2007 Honda BF9.9/10D - Replacement Carburettor Confusion

[robbob]

Hi All;

I am in Europe (Ireland) and I have got a second-hand 2007 BF10D for a sailboat. This would be exactly the same as the 9.9 in the States - well, that is what I thought!

VIN is BABJ-1306966
The other ID plate says it is 2007, BF10D (HNX0222G0)

This is a tiller steered, electric start (plus manual), automatic choke, long shaft version.

This engine was a little neglected (but running), so far I have done the usual - impeller, cleaned out the lower unit, gear oil, motor oil, new sparkplugs, new fuel line and bulb, restored coolant water flow due to blockages..

Compression is fine and she runs first pull (and via starter motor), but does not like to go above idle. Dies when I throttle up. Thermostat is fine (cleaned all that area out and tested it in boiling water) - but will replace anyway. But I don't think it's overheating, because using carb cleaner in the air intake while running got her revving up for a while. So I am guessing carb jets are blocked or maybe the gaskets are bad.

Cleaning the carb and replacing the gaskets is the obvious first step but I thought it would be better to replace the carb assembly entirely and clean the original, keeping it as a spare.

So, I go over to SVB24.de (a German chandlery) and they offer a replacement carb for 126€ - great deal I think.

The parts number for this carb assy is 16100-ZW9-G01.

Then I decide to double check the parts diagrams on the SVB site, and I notice they say that they are for the >2012 models.
https://www.svb24.com/en/spare-parts/spare-parts-for-outboards-honda-outboards-bf10.html

Most items are identical to previous models (motor design seems unchanged since 2003), but of course, not the carb.:rolleyes:

I can’t seem to find an EU/ROW parts finder database online. The official Honda parts site is US only - and doesn’t recognise my serial number!

So I go to the US ones, like boats.net. Here I find my VIN number (BABJ-1306966) corresponds to a 2004 BF9.9D4 LHSA model (well, without the “A” for “American” I presume). This is a bit funny as my engine is 2007. Nevertheless, the carb assy parts numbers are identical between the 2003-2007 models.

I come across this thread:
http://www.marineengine.com/boat-fo...9-Tiller-poor-running&highlight=16100-ZW9-716

Which confirms that manual/auto start need different carbs and won’t be compatible..

The correct carb for my model is 16100-ZW9-816 according to the parts diagram.
https://www.boats.net/catalog/honda...-babj-1300001-to-babj-1399999/carburetor-auto

Well of course this is more expensive than the >2012 one from Germany, but, ok. I shop around and see on Defender the same carb:
https://www.defender.com/product.jsp?id=1829803

Note, this says,
“Identification: Replacement for Carburetors Stamped BJ02BD
Please be sure to check your stamp before ordering”

Good idea!

So I check my carb and it is stamped:
14B(A) V105

???

The carb on SVB for the >2012 models is "BJ14A A" apparently, so also different.

I google image search various Honda BF10s but in all of them, the code on the carb is never legible - nor is it visible on product photos..

So the question is -

- What the hell is the right carb for my model and where can I find it??

I don’t want to order something from the US that ends up being the wrong part because of some obscure EPA/EU emissions regulations…

Hopefully someone here will have an idea, I am stumped!

 

[robbob]

Some photos:

 

[jgmo]

Hi,
Your story leaves me probably more confused than you are.So many numbers! And no match!
I feel your pain.

I have to admit I have no clue as to what you need.

I can't make out clearly, from your photos, details I would like to see. But, looking at the throttle linkage return spring and, what I think is the accelerator pump belllows, your carb looks to be different from what is available on boats.net. It could just be my bad eyes but I'm saying yours is different in my opinion.

You might see if you could figure out how to contact Keihin and see if they might help you using that stamped number.

I agree with having a spare carb if it's affordable but, since these carbs can be difficult to properly clean, you wouldn't know if your old one would work unless you bolt it up and try it. So, I suggest that you carefully clean
yours while you figure out what to buy.

However....

....Since you don't know how to correctly source parts, you would need to reuse the seals and gaskets. I never recommend reusing seals and gaskets but, in this case, I'm not sure there's any alternative unless you can positively identify what you have.

The paper gaskets are easy to reuse if you're careful taking them off and there is really only one critical internal seal...a tiny oring on the jet-set tube....and I have reused those before too.

I wish you the best of luck.

 

[robbob]

Hi Jgmo,

Thanks for your help! I've been reading older threads and what I get from them is that cleaning these carbs (I think I have part of the carb cleaning manual somewhere) - is very tricky.

Luckily regarding the seals and gaskets,

16221-ZW9-000
16211-ZW9-000

These appear to be exactly the same between models since 2003 up to now?

So I will order these from an EU supplier and see if can get an ultrasonic cleaner.

I'll upload more photos soon to see if that helps.

Can't believe that it is so convoluted to just get a replacement carb!

I am wondering if my model is the same as the BJ02BD carb but a different manufacturer? I read somewhere Honda uses a couple of external companies to source their carbs?

 

[jgmo]

Well, I have the 2018 publication of the carb manual (6th edition) and it states that, theoretically, carbs of the 9.9D "genre" SHOULD be BJ model coded.
BUT...
...it does not go into any detail about the 10D outboards???
I have never seen a 10D outboard but you would certainly THINK that they would be extremely similar to the 9.9D. I just don't know.

In the photo you sent of your carb model stamp though, the manufacturer, Keihin, is clearly visible in the casting. Which does make sense to me and why I thought contacting that company might shed some light on this for you.

 

[jgmo]

As an aside, I had read somewhere once that the 9.9 hp rating for most outboard manufacturers was due to horsepower limits on many small lakes and was an easy way to market/sell their 10 hp outboards without doing anything other than swapping a decal.

 

[jgmo]

The mount gasket you listed (16221-ZW9-000) is what I would expect. However, the insulator...16211-ZW9-700...is almost always reusable unless mishandled and cracked. I would NOT order one of those. See items 21 & 22 in the link below.

https://www.boats.net/catalog/honda...-babj-1600001-to-babj-1699999/carburetor-auto

The critical tiny oring I spoke of is only available with the purchase of the jet set tube (16150-ZW9-003)...item 18 in the link OR by purchasing the gasket set (16010-ZW9-003)...item 1 in the link.

I can tell you from experience that finding those tiny orings locally can be a challenge. And that particular one will cause you no end of headaches if it is loose and doesn't seal the tube properly.

I would normally suggest to most that buying a new jet-set tube is the way to go. That tube gets partially plugged in the internal orifice and can be VERY difficult to clear because it is so hard to see inside. The tubes also have a tendency to crack vertically from vibration or overtightening the retaining plug that secures the emulsion tube.

I would also buy the gasket set because the float chamber seal can deform in some instances and won't reseal. Ethanol treated gasoline can cause that.

Ultrasonic cleaners are great tools...I own two...but I don't rely on that alone to thoroughly clean these carbs. Sometimes it works, sometimes not. I always use carb spray to blow out critical passages such as the carb throat delivery orifices, the accelerator pump spray tube and orifice and the high and low speed air jets. Oh, and that jet-set tube when I don't have a new one to install.

I will be happy to "walk" you through the process if you need it. It's actually been awhile since I cleaned one of these but I still remember how it's done.

It would be great if you could post more photos of the carb but I know it's a pain. The file size limits for pictures on this site has always given me trouble and the pics come out grainy and out of focus. Some guys know how to overcome that and post some spectacularly detailed photos but I haven't figured it out.

 

[robbob]

Hi Jgmo,

Thanks, great tips!

As it happens I have a PDF of the 2001 BF8D/10D/etc Honda Service Manual. This includes a very detailed description of taking apart and cleaning the carb, amongst other things.

Flicking through it everything seems identical to my engine but I do need to check that in detail. I keep wondering what the differences between the carbs are?

I mean apart from the manual/auto and the HP rating. US vs EU.. I think I read on this forum that one change was just deleting the slot in the idle screw so it was impossible to adjust without taking a Dremel to it...

Like you, I was under the impression that the only difference between the US 9.9D and the 10D was the label. Seems not.

An ultrasonic cleaner would be very useful for other parts (also restoring a Yamaha 8C) but I have a can of carb cleaner as well, of course. And compressed air..

I forgot to mention earlier I also greased all nipples and replaced the internal fuel filter already.

More photos no problem, but I haven't taken it out of the engine yet:

Here the auto choke throttle linkage, seems to work fine:

Drain screw (Drained it before I did anything, nothing came out)

Hopefully a better view ...

 

[robbob]

Also, for context, I do want to renovate this engine fully as a new one would be very expensive (duh).

A previous owner misplaced the rubber seal on the lower cowling port side; this allowed salt spray to penetrate upwards under the cowling. This has caused superficial rusting of various brackets and nut heads; however that seems to be mostly cosmetic. I'd be more worried about the long-term reliability of the wiring. But, battery start, starter motor, sparks, and charging seem to be all fine so far (touch wood).

There was a lot of salt deposit build up inside the cooling tubes, which required removal to get her peeing again. I've read on this forum about using warm vinegar instead of mechanical removal; I do want to run with SaltAway first and see what happens to remaining deposits..

Previous owner also let the leg in the water for about 6 months on a mooring (salt water estuary) :rolleyes: - this resulted in a crustacean infestation in the lower unit - all cleaned out, pump housing renovated and impeller replaced - still ugly pitting corrosion on the exterior. Which I will clean up, epoxy, and spray. Gear oil replaced, shaft and prop and gears seem fine, no milky oil when drained.

So going forward, apart from the carb cleaning and the above, plan is to:

- Replace missing lower cover seal - 63719-ZW9-000
- Replace cowling seal (of course this is loose and cracking in places) - 63102-ZW9-310
- Replace thermostat - 19300-ZW9-003
- Replace internal fuel lines to carb/fuel pump - 16861-ZW9-000
- Replace internal anode - 12155-ZV4-A00
- Replace cooling housing gasket - 19371-ZW9-000
- Replace muffler plate gasket - 17384-ZW9-010
- Replace timing belt - 14400-ZW9-004
- Replace thermostat - 19300-ZW9-003
- Install water/fuel separator between (new) tank and primer bulb

Not sure if I'm forgetting something important... Should keep me busy for the winter...

 

[jgmo]

Well, the biggest difference I think I notice is that your carb doesn't appear to have the plastic tamper proof idle mixture "screw". I'm not positive because the photo isn't directly from the side. Other than that it looks pretty familiar to me.

Your action plan sounds good to me. You didn't list oil and filter change but I assume that's because you probably did that first thing.
I would only add that you replace the anode attachment with the anode because they weaken and break over time. It's worth the 82 cents.

I also suggest removing the propeller and inspect the thrust washer. Any wear at all would have me replacing that item out of hand. I keep a spare new one just because.

It is a good practice to remove the prop from time to time and keep that thrust washer "fresh" to protect the transmission and, at the same time, remove any line or debris that wraps around the shaft. Monofiliment fishing line is probably the #1 killer of prop shaft seals.

Lastly, I would urge you to check/adjust valve lash.

You stated that you backed out the carb drain screw and nothing came out?....hmmm. Nothing at all? If so, that is suspicious unless you diconnected the fuel line and idled the engine until it quit as most people do when putting the tank away.

I will tell you that the feed passage to that drain along with the passage that supplies the accelerator pump piston are both in the bottom of the float chamber. On a very dirty carb, those passages will pack up with "mud" and need to be poked clean with a small piece of wire.

I will also tell you that, unless that accelerator pump circuit is perfectly clean and open, that outboard will never run correctly. That is something they don't tell you in any of the books and it drove me crazy when I first started working on these carbs.

Good luck and please keep posting your progress.

Eirinn go Brach!

 

[robbob]

Yeah, nothing came out of the carb. I figured this was because the mechanic let the motor idle out, but who knows.

So it seems like the only differences regarding the carb is the idle screw? In the US they remove the slot in the screw and in the EU they seal it off entirely? "Will no-one rid me of this turbulent priest?"

If gaskets, internal seals, and jet set are identical, differences in carbs must be minimal, doubt Honda would want to change more components than the minimum...

Oil and filter were changed last year by a mechanic, then by me. Honda brand oil.

Good idea for the anode attachment - I assume you mean 93500-05020-4J ?

Prop I already took off, no fishing line. Examined the thrust washer - photos attached after cleaning off the grease and loose dirt. Dirty (a few molluscs were still on it). But no wear. I will order a new thrust washer anyway.

I actually have a spare prop; and seem to have misplaced the castle nut again... Both props are in ok condition but the high thrust 4-blade version would be best for a 2.5tonne sailboat I think. Existing ones are 3-blade stock.

Valve clearance sounds like a good idea. Saw a Danger Stu video on a BF40, looks straightforward. Should be done before or after replacing timing belt I wonder?

Thanks again - I am very eager to learn things they don't tell you in the books!

 

[jgmo]

Do you think the idle mix needle screw is hidden behind an expansion plug? I mean there HAS to be one, right? IDK....??

Yes, that is the anode mount screw part number. They break off flush sometimes and are very hard to dig/drill out.

I would adjust the valves after the belt replacement.

The thrust washer contact area on your gearcase looks pristine! I would venture a guess that this outboard doesn't have many hours on it.

Ahh, a sailboat in Ireland! I tried to rent one in Kinsale when I was there for the Rose of Tralee pageant with my daughter. I quickly found out I didn't have that kind of money! The hotel concierge in Dublin got me great deal on a really underpowered little Opal suv though! I just had to learn how to drive all over again ;>).....Whew! We made it!

What boat do you have?

 

[robbob]

Jgmo,

Nice story! I have a Leisure 23 - in Kinsale!

My guess is also that there are not that many hours on this engine. As usual owner neglect is more of an issue than overuse.

Not that mechanics are necessarily better. I measured the oil level with the dipstick before running - and it was overfilled! Which is why I changed the oil despite it being "serviced".

I'll see if I can find the idle mix screw..

 

[jgmo]

4k lbs. Half again heavier than my San Juan 23. You will actually use all that Honda will give.
Fin or bilge keel?
I watched a video of some guy having his girlfriend sand and paint the bottom on an L23. The twin keel made it "a very convenient arrangement" if you get my drift ;>)

 

[robbob]

Hi jgmo - your San Juan 23 is very similar in dimensions to my L23 but no doubt performs much better in light airs. On mine my 135% Genoa does most of the work - pretty small main (masthead). She is quite seaworthy for her size - a bit of a pocket cruiser - designed for the North Sea. Reminds me of a Coronado 25 or a small version of a Pearson Triton.. It's good that I'm a fan of the "classic" look!

Different beasts to the Beneteau 37/41's which you would rent from Sovereign Sailing down the road, which I assume were the company you were interested in renting from.

She is a bilge keel which has a few advantages here - it's quite tidal, like Maine. But ease of painting isn't one of them any more - she's been Coppercoated!

I think a lot of L23 owners these days use a Tohatsu 6 SailPro, extra long shaft. I have to say, being half the weight of my Honda is very appealing to consider! Especially as the motor is not in a well but on a stern bracket (I had to replace the old one which crumpled because of the weight in rough seas.) But the Honda is quiet and efficient, even with the stock prop. An extra-long shaft version would be a nice upgrade, but they seem to be very rare.

 

[jgmo]

Oh yes!

Little Wing....my boat's name....sails like a dream! She points very high for a shoal draft centerboard boat and RIPS downwind with the board retracted. Like your Liesure, the main is pretty small and the power is all in the headsails.

But the boat will answer the helm in a whisper of wind and sailing her into a slip or picking up a mooring with just the main up is virtually childs play.

I had an old Chrysler 6hp 2 stroke smoker/noise maker that, when I learned the boat, got taken off the bracket and stowed below the cockpit. I ultimately gave that thing away to a buddy for his trade school engine rebuild class.

Outboard? Outboard??? We dohn need no stinkin' outboard!

BUT......
Venture out into the North Sea in a SJ 23?? NO THANKS! Motor or no motor!


I used to get pretty nervous off San Diego's Point Loma on a sunny day with a small swell running!

I like to say shortening sail and reefing MUST be in a San Juan skipper's blood!

 

[robbob]

Well jgmo, I’ve finally got around to removing my carb for cleaning with the ultrasonic and carb cleaner.



I have the jet set and gasket set you recommended.

I was wondering, what is the deal with the accelerator pump? How do I know if I’ve got it perfectly clean, or is there a way to disable it without any negative side effects?

Engine still runs - first pull. I have hardly ran it since the Spring unfortunately as I was busy doing other refit work.

I have the Honda service manual but not sure what additional tips you recommend for this process. There are different threads with interesting information over the last years but it’s hard to put it all together.

 

[jgmo]

Hi robbob,

Welcome back!

Well, the pump itself..ie: piston and spring... is really of no consequence. What REALLY matters is the accelerator pump nozzle and tube portion of the circuit.

The brass tube can easily be seen jutting out horizontally into the air stream at the Inlet side of the carb throat. The nozzle is at the tip of that tube facing the outlet side of the carb throat or, in other words, the throttle plate.

If that tube and/or nozzle get plugged, the engine won't run well at all.

You need to remove the float chamber and find the passage that feeds the tube in the main carb body in order to test and clean both tube and nozzle.

Do this:
With the float chamber removed, find a way to prop the throttle wide open so that the throttle plate is horizontal to the carb throat. I use a pocket screwdriver to do this but many items will work.

With the throttle wide open, you can now sight through the carb throat from the outlet end and see the tiny accelerator pump nozzle in the end of the brass tube looking back at you.

You need to take your can of carb spray with the plastic spray straw attached and insert the straw through the outlet end of the carb throat. Carefully place the end of the straw over the tube nozzle and give it a shot of fluid. If the nozzle and tube aren't completely plugged, fluid will come out the inlet to the tube feed. If so, you need to spray fluid into that opening. If no fluid comes out of the nozzle as a result then try spraying the nozzle several more times. Hopefully, that will start to clear the blockage.

If not, you will then need to locate the feed opening by finding the accelerator pump piston outlet in the float chamber and use that as your guide to find the opening in the main body. Once you locate the opening, spray into it attempting to unblock the tube and nozzle. What works best is spray into the opening and then spray into the nozzle. Back and forth, back and forth until you start getting some fluid to push through to the other end.

I have never been unable to unblock a tube and nozzle in this manner although it can take quite a while and a lot of fluid. More than one can sometimes.
A sonic cleaner might help in this process but I wouldn't bank on it.

The bottom line is this:
That tube and nozzle need to be clear enough so that when you spray into the feed opening, a solid stream of fluid shoots out past the open throttle plate approximately 8 feet.

Yes! 8 feet! If not, keep cleaning.

If that nozzle or tube is plugged....even a little....your outboard won't reliably make power even if the accelerator pump is brand new.

Good luck.

 

[robbob]

Hey, thanks for the advice again! Hope you had some fine sailing this season.

I disassembled the carb according to the shop manual.

Everything on my carb seems identical to the shop manual (which is from 2003).

I found the accelerator pump nozzle and indeed it was blocked!

After an hour in the ultrasonic cleaner (I used distilled water mixed with an appropriate alu-safe degreaser), and liberal spraying with carb cleaner, the nozzle now sprays clear and far, as do the others.

Now, here’s the funny thing.

I got a new jet set #45 as is appropriate for my model. That is part No. 16150-ZW9-003.

Well, my old one is different. It is #42!

I took a photo, attached. You can see that it is slightly different.

I have attached photos from all sides of the carb body as well.

I am now wondering if my carb is from another engine?

Or if I even have some sort of Frankenstein engine?

As mentioned before the plate says she is from 2007, BF10D HNX0222G0.

But the SN/VIN are says BABJ-1306966, which is the 2004 D4 sub variant according to boats.net.

Then again, an ID sticker for the chassis says BEABJ-2006419. Suggesting 2006/7.

I’ve replaced o-Rings, checked float valve, etc as per the shop manual but I did not replace the #42 jet. I will run her tomorrow to see if the issues are fixed but I am tempted to just get an all new carburettor from Impex and be done with it!

Be interested to see if you can shed some light on this …

 

[jgmo]

Well, I don't have the answer to your question. Interestingly enough, the dedicated Honda carb manual makes no mention of a 10hp model. Not even in the context of "9.9/10" type of description. But, then, I'm not sure that I have the most recent publication. My latest is the sixth edition printed May 2018.

I might have tried installing the #45 to see what would happen but that's just me. Although, your comparison photo does show some physical differences so it might not work so well at all. You probably did the right thing installing the old one if all you want is to "get on with it".

If your description of the accelerator pump spray nozzle delivering liquid "far" equates to spraying a stream 8 feet past the throttle plate (as I previously described) then I'm predicting that you will be happy with the result and performance.

Good luck on the test drive and looking forward to your triumphant report of success.

 

[robbob]

JGMO;

I presume 9.9 is the 10HP model, only the sticker is different.

My 2001 copy of the carburetion manual (I only have Chapter 7) states that Jet #42 is used in:

BF8A**
BF45A
BF50A
BF75A

This old version doesn’t have the newer D range (these were in 2003), what does yours say? I am citing P7-3.

My suspicion is that someone swapped out the carb from one of these models. (Well, or the D equivalents). The previous engine on the boat was also a Honda, so it could even be from that one!

AsFAICT the correct carb would have the #45 jet, as this is what boats.net diagrams and part numbers show.

There’s an additional notch in the #45, so the fuel/air mixture with a #42 jet will be different to what is expected, which is unlikely to help the engine to run better IMO.

 

[robbob]

Looking at some old documents it says the original engine on the boat was a Honda 9.9, 4Str, SN BG03AADD…

 

[robbob]

Looking at some old documents it says the original engine on the boat was a Honda 9.9, 4Str, SN BG03AADD…

I was just looking for prices for a new carb - going by the latest 16100-ZW9-G11 part number as the older 16100-ZW9-816 version is hard to find …

And I come across a website with this photo:


That’s “14BA” …

 

[robbob]

And according to the German SVB site parts finder mentioned in my original post .. the jet set part number for this carb (G11) is …

16150-ZW9-G01

Which is #42!

So the mystery is solved. I already have the latest version of the carburettor, which is “post 2012” according to SVB even though boats.net and yumbo only list “2007 and later”.

Go figure …

 

[jgmo]

Well....

interestingly enough my carb manual shows the 45 jet set specified for both the 9.9A and the 9.9D.
(page 7-3)......so.....

I don't know.

It may be that the later model "downsize" (if that's what it was?)....
....was due to accommodate some governmental emissions rule or something.

Again, I don't know.

 

[robbob]

Well, I managed to put everything back together. Sort of.

I don’t know what it is with Honda, adjusting or serivicing anything is extremely fiddly and awkward to access compared to my Yamaha and Tohatsu.

No matter how I adjusted the throttle shift cable as according to the shop manual and common sense, at idle the lever no longer lifted the spring lever of the accelerator pump.

It was good before I took it out. So something has gone wrong with the spring inside the carb. Or the throttle cable.

She started up first pull, and no longer dies above idle, and she sounds good I guess (using muffs with engine covers off)

Activating the accelerator pump manually while running at the carb didn’t seem to do anything of note. It was obvious that it wasn’t really working because the throttle changes were kinda rough and not smooth as you’d expect.

I’m not messing around with the carb anymore.

I will simply order a new one. Not dealing with this hassle in the future. And looks like a new throttle cable as well. To be honest I am on the verge of parting out this engine and replacing with a Tohatsu SailPro.

 

[jgmo]

The accelerator pumps on ALL these carbs are pure junk! They only work when brand new but that means getting a new float chamber to get a new piston bore. Not worth the $$$.
Your piston is likely cocking in the bore and hanging up. Lightly sanding the bore and the piston can get it working for a time but it will hang again soon.
I agree with the new carb purchase.

 

[jgmo]

I went back through and read the thread because I usually warn people about the accelerator pump being a useless device on these carbs. But it looks like I didn't give you a heads up about that so I apologize for the omission.

It's crazy too because the accelerator pump nozzle is SO important to keep cleat!

I have run these carbs with the accelerator pump piston and spring completely removed and I see little to no difference in performance.

As a result, I stopped buying new float chambers and pump kits for our fleet of 8D and 20D outboards. Instead I just made sure the nozzle and tube was clear and I ran a coarse Dremel sanding barrel in the bore to remove enough metal so that the piston wouldn't bind. No more accelerator pump problems and no complaints.

 

[robbob]

That’s interesting. Your method would ensure the accelerator jet would always be pumping right? Just bunging in a new carb seems simpler though.

I still have my timing belt and thermostat to replace. And then the valve lash. Earlier this year I noticed the compression (from cold after water storage) was lower than I’d like, about 120 in both cylinders. I’ll run her again tomorrow and recheck the comp warm after a while running.

I replaced two of the three internal fuel lines just in case, but the old ones looked perfect inside. I should do the third one too as it’s more likely to be an issue (the line from the external connect to the fuel filter).

In your experience what else is most likely to fail in one of these motors ? Fuel pump? Oil pump? Wiring? CDI? Anything specific?

The government has mandated E10 here - it’s important to destroy the Borneo rainforest quicker - I treat with E10 stabiliser and run carb dry but I don’t trust it’s effects.

See attached photos for a demo of the accelerator issue. Can’t seem to attach vids. You can see that the throttle lever hits the stopper fully closed.

 

[jgmo]

No, my method would have the accelerator pump circuit basically doing NOTHING....
....pretty much what it's already doing after a few hundred strokes and a little bit of wear. It's a problematic, USELESS system on an otherwise EXCELLENT piece of equipment.
Why it's so ABSOLUTELY necessary to keep that brass tube and spray orifice clear I can't answer with any facts. I do suspect though that it acts somewhat as a system vent in some way because, as you've proven to yourself, the carb just doesn't work well when it's plugged up.

The carb IS the weak link on these outboards. I've not had experience with ANY of the items you listed failing although I'm sure it's happened to someone. Anything mechanical or electrical in nature IS eventually going to go south.
But....
.....Honda built these outboards TOUGH. All things supposed to be hard ARE hard....unlike stuff on your proposed replacement motor. The systems are RELIABLE and CAN take a beating. These outboards survived 15 years of daily rental service...general abuse...collision (rocks, boats docks, trees)....idiots and drunks making "adjustments"... and a couple of sinkings! All while I watched. The most often replaced parts were thrust washers, props and carburetor parts. Those and spark plugs, filters, oils, impellers. Almost NOTHING else!
An ignition coil here, prop shaft seals, indicator lamp there, a couple of trim unit rebuilds, fuel line disconnects and so on. No pumps, no CDI units. Wiring? YES! The trim control relays on these break the wires off right at the relay housing. But I could usually save them with a soldered on pigtail repair.

OH!...and two VERY EXPENSIVE (dealer cost) gear case assemblies! Assemblies that failed beyond repair because the gear oil wasn't checked for 5 years and water got in. They were run with water for lube until catastrophic failure occurred.

And that's after going FIVE YEARS without ONE oil change or waterpump service before I came along and insisted on some maintenance being done. (That's how I got paid).

I didn't know Honda before that but I quickly gained a loving respect for them during my time there. So much so that I still have my '06 20D....big brother to your 9.9.

Most carb issues in that arena stemmed from fuel with water in it being not drained. They had their own gas station that had leaking tanks. It was so bad that I finally convinced them to fuel all the boats with gas from town via big Gas Buddy tanks hauled in pickup trucks a few times a week. Down time fell significantly.

I never did get the facilities manager to have the dock hands close the fuel tank vents every day so water would still develop in the tanks. Especially after any rainfall.
They were still happy selling the contaminated gas at three times the priceto all motorists and boaters that pulled up though. First $6 a gallon "gas" I ever saw pre Joe B!
That is, until the State Weghts and Measures inspector filed a report. Not sure if that filling station is still operational today.

BE VERY CAREFUL WHERE YOU BUY FUEL AND TEST IT OFTEN.

Running the fuel out is good but doing that and then opening the float chamber drain to ensure it's dry is better. At least the first couple of times to make sure it's actually getting dry.

You're not getting full throttle?

Is that throttle cable new? If so, is it OEM? I ask because it looks too long to me.
Stretched maybe?

I don't know.