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Honda BF9.9DK3 Woes

soggyhalyard

New member
Hi all, I have a Honda BF9.9DK3. Not sure what year but early 2010s I believe. I’ve been pulling my hair out and hoping someone can point me in the right direction before I decide this thing is just going to be my new boat anchor.

Here is the story:

I’m sailing in a remote region. About a six weeks ago my engine starts acting up, harder to start, stalling, needing longer to warm up and stalling on acceleration. I had not winterized it the previous year, was running year old fuel through it, and think I might have sprayed some water in vent of my fuel tank when washing my deck.

Clearly a carb issue. The issue got progressively worse and worse until I couldn’t ignore it. I disposed of my gas, cleaned the tank, got new gas, removed the carb and cleaned it the best I could. The issues still remained but changed so I figured I just was not able to sufficiently clean the carb. The issue turned to only being able to run with the choke at idle, and only being able to get to high RPM using the choke, poor idling, etc. After a few more carb cleanings the engine was idling again and could go to high RPMs with the choke to accelerate so clearly something was wrong with the accelerator jet. I ended up removing the little ball and snap ring at the bottom of the accelerator pump. This fixed the issue and the engine was running well but noticeably rich. Smoke, smell, etc. I was only going to run it like this for a week or so until I got to a parts store but things got worse again.

Finally I got to land. I replaced the carb, new gaskets, new spark plugs (which were heavily fouled after a few hours of running rich). Got new fuel and installed a racor fuel water gasoline separator with 10 micron filter, new fuel line and bulb; did an oil change, replaced the gear oil (maybe a little low but I put it in a unmarked container so maybe not, color was okay), sprayed the whole engine down with T9, ran it on the stand in neutral and it ran great and idled well. Sweet, although there seems to be a little smoke coming from the lower exhaust, okay… maybe spraying T9 on everything was not a great idea and it’s burning off.

I put it back on my dinghy. Idle is good, maybe not perfect but it’s not stalling. Low speed is good. There is definitely smoke but it’s not a lot and not overly rich smelling. Big problem is the engine will not reach high RPMs. It stutters a little at about 60% WOT and then continues at any throttle over 60% like I’m sitting at 40% throttle (in terms of RPM sound and thrust).

I don’t think it’s a spun prop because the engine is not running that hard. I thought maybe fuel pump but pumping the bulb while running doesn’t make a difference. The condition seems stable to. I’ve ran it for maybe 20 minutes trying different things here and there and nothing is changing. The fuel being run through is the fuel recently purchased with Heet added.

Can some one give me some pointers on what to do next? This is killing me!
 
Soggyhalyard...not pleasant in the early morning but far better than frozenhalyard :LOL:

Sorry, couldn't resist.

An odd set of symptoms for sure.

My first thought when reading the beginning of your post was "thermostat stuck open".
That's still at the top of my list, especially if you are operating in very cold water.

You mentioned spun prop. You can check that by marking the the inner and outer hub and then checking to see if the marks remain aligned after a run. Magic marker works good short term but two clear scratch marks will always be there for reference.

Other things that I think might cause what you're describing are:
Cam timing ....is the belt tight and do marks align as they should?

Valve clearances...it might be time to pull the cover and do a check.

Hopefully you have the shop manual. I don't so I can't provide you the specifications.

Beyond those things, you mention using the choke to keep it running.

Did your new carb come with a new choke cable assembly?
I ask because these don't have a conventional "butterfly" choke.

Instead, they have what they call the "Service Enrichment" or SE system.

On the end of the choke cable is a small "pellet" that is the valve that opens and closes the system.

Consequently, if the cable gets stretched or kinked or the cable housing is worn or damaged in any way, the "choke" will no longer work properly and will cause problems.

That's all I have at the moment.

Good luck.
 
Few things worse than a soggy frozen halyard :ROFLMAO:

Thanks for the thoughts, jgmo.

Since I don't know how old the thermostat is I replaced it. In the process snapped the upper bolt to the thermostat cover deep. Drilled it and when extracting it, the screw hole on the engine block broke away... Great. I'll be able to secure it with a bolt and washer now but not a great start.

The choke cable has damage and I can't source a new one for two more weeks but I'm relatively sure it's fully depressed. It's in the mail and it won't hurt to check all the other items you mentioned in the meantime.
  • Spun prop
  • Cam timing
  • Valve clearances
If you have any other thoughts that pop up, please share them.
 
Hi,
The damaged choke cable is a problem because they are not very easy to change. It looks simple but can be a real pain.

First of all you shouldn't try to replace just the cable. If the cable is damaged then you MUST also replace the "valve set, starter"....see item 12 in the link.

The "valve set" is really nothing more than the housing that guides the cable into the carb.

Honda used to sell the cable already installed into the "valve set" but now people tell me they only sell the two separately and you have to assemble them yourself. WHAT A RIP OFF!

Anyway, I know from experience that trying to use a new cable in a used "valve set" is a waste of time and won't work well.


Sorry for the glum news but been there, got the T-shirt.

Good luck.
 
Okay, thanks for the information. That's good to know. The new carb I bought did come with the valve set. I stowed it and just installed the old valve set/ damaged cable. Hopefully installing the new cable coming in two weeks into the new valve set won't be too big of a pain. Wouldn't it be nice if that solved it.

If I just installed the new valve set (#12) without installing any cable, would that be the same as a not-engaged choke so I could verify if that is the issue? The spring in the valve set would be pressing that little pill down so it seems like it would. I want to avoid taking and reinstalling the carb too many more times.
 
The."little pill" at the end of the cable shuts off the extra fuel for starting when it's all the way down. So, not having the cable installed would be the same as FULL CHOKE or rich mixture.
That should have the engine starting easily when cold with elevated idle. After about 60 to 90 seconds running like that the mixture will be too rich for a rapidly warming engine and at about 3 minutes in the idle will probably be pretty ragged and she will likely stall and be difficult to restart until cool again.

Don't underestimate the difficulty of fitting the cable and valve together. Go slowly and carefully because, you can ruin the valve or cable or both and then will need to order again.
I DON'T LIKE those little devils!

I found a VERY SMALL amount of Vaseline in the boot entrance can make assembly easier but too much is not good.

Also, note that the threads on the valve are plastic and can easily strip if slightly over tightened. BUT....if you don't get it cinched down well enough to stay tight, it can loosen over time and vibration will strip it for you ANYWAY! I have found several ruined like that. Once the threads are stripped, it's toast and won't work.

Did I say I DON'T LIKE THOSE DANGED THINGS?

I have never run one with the cable removed so I don't know if there's a danger of fuel splashing out on you. Just keep an eye out for that if you try!

Good luck
 
So, quick follow up to this journey.

I swapped out the carb. Using the vaseline trick it was pretty straight forward. Ran the engine and no improvement. At this point I was running out of time and dropped the outboard off at the local service shop. They called me back and told me I overfilled it with oil by about a third of a quart, no other issues.

Being a bit skeptical I asked if they tested it under load. They did in a tank but can't fully load it. Unfortunately my dinghy was packed up and I was schedule to fly out that afternoon so I couldn't test it in the water but I'm going to operate under the assumption that all is well now and I'm a doofus. Happy the saga is over.

Thanks, jgmo for your help.
 
Hmmmm...

Well, these  can be pretty sensitive to overfilling the crankcase.

Hondadude (who always knew a heck of a lot more than me) used to always say "leave the oil just a bit low".

Sorry, that never crossed my mind for this.

So, I guess we'll see. Hope that's all it was anyway.

Good luck and let us know.
 
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