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2006 Honda bf9.9 starts fine, runs well at low rpm but won’t rev up past half throttle.

W

Warkmeister

New member
Hello all. First post but I’ve search for weeks on this.

2006 bf9.9D6 lsha (babj1500030) starts fine, carb mix is at 3 turns out, 45 slow jet (stock), 100 main jet (stock is 102 but I run at 3-6000 ft elevation). Float height measures within range. The issue I can’t figure out is that it seems to not like or be able to rev past half throttle. Issue existed with 102 jet as well. It surges and sounds like it’s struggling to eat fuel, regardless or increased throttle position past half. Occurs under load or in neutral, with muffs or in the lake. I’ve replaced spark Plugs, which seemed to help a little, but no cure. Also replaced auto choke. I’m curious if there could be a non mechanical issue? Could the cdi be failing? Or would a bad coil behave this way?
 
Hi,
Sorry you're having problems.

Tiller or remote control?

To kinda, sorta answer your questions about CDI, ignition coil or exciter coil being a possible cause.....I don't think so.

While anything is within the realm of possibility, my number one suspect for this is the finicky little carburetor that is fitted to these wonderful twin Hondas. It probably needs a thorough cleaning.

But, first check that when you ask for full throttle, the carburetor throttle arm is moving all the way to the stop. Just had a case here recently with a 9.9 D where the cable housing wasn't secure and full throttle wasn't being achieved.

I would also take a close look at valve timing and valve adjustment. Make sure the the timing marks are properly aligned and that the timing belt is in good condition and not stretched or loose.

If you don't know when the last valve lash adjustment was then it's time to check that.

If all that is in order then I suggest that the carb be P.R.O.P.E.R.L.Y. cleaned.

I emphasize that because there's more to it than most people realize. Basically, it's a pain.
But....completely do-able and, more than likely, necessary to get your baby back "up to snuff".
 
Thanks for the thorough reply. I was hoping someone familiar with these engines would answer, and it sounds like I got it. It’s remote controlled. It came with a brand new, proper keihin carb from the boat shop I bought it from, but never ran as well for me as it did when I bought it. I’ve had it for a year and a half, and never checked the valve train. I guess I assumed the shop mechs adjusted and checked it all before I bought it, but that’s most likely naive. I will clean the carb and look into the valve adjustment. Throttle cable is getting full unrestricted travel.
 
Hmmm.

As far as assuming the boys at the shop did you any favors....don't. 99 out of 100 times they're more worried about what's for lunch tomorrow so, even if they did do something.....can their work be trusted? Maybe.....maybe not.

And as far as the N.E.W carb goes....
That term stands for:
N.ever E.ver W.orked
I learned not to trust "new" many moon ago.
I have had foundry casting sand pour out of sealed Honda carb parts bags before. NO! REALLY!!!

And, after watching your really excellent video, I wonder if the float got set correctly in that carb? It could be a little low shutting the needle prematurely. Make sure you check that if you go in there. The float should be basically level when the carb is held upside-down.



Does your primer bulb stay nice and firm while this is happening?
Have you tried squeezing it while running to see if there's any improvement?

These little Keihin carbs took me to school on my first go with them.
Yours has an accelerator pump. The most USELESS accelerator pump I've ever encountered. I have removed the pump piston before and had ZERO performance complaints.
The piston can be siezed in the bore....the Inlet check ball can be rattling around or missing and you'd never notice the difference.
BUT.....
Let the delivery passage for that pump get the least bit plugged (and they do frequently) and the outboard almost refuses to run.
Special attention needs to given to that passage and I have a fool proof test if you're interested.

Also, MOST (and I'm talking "experienced" shop techs) people miss a bunch of things when it comes to cleaning them. While I know people have success using ultrasonic cleaners (I have two) they don't always get the job done. I prefer spray cleaner, compressed air and technique to hose these babies out.

I don't mind helping you or answering questions and, as I'm sure you can see, I'm a bit "wordy". So, if you find my missives make your eyeballs sore, SORRY! Can't help it.

Good luck.
 
first off, wordy is good when it comes to gathering knowledge! Secondly, thanks again.

Carb will come off tonight to get cleaned out, I’ll do my best to blow the cobwebs and passages out.

I’ve done some of what you mentioned in the recent past, ran off auxiliary tank while squeezing the bulb to ensure it’s not a flow issue….same results.

I did just reset the float prior to that video, but it ran essentially the same before. I followed a procedure that described a 13-15mm free end float height when the plunger just begins to unseat…while upside down. I feel like I’ve read 2 or 3 different procedures in various carb orientations. I’ll try yours and see how it runs tomorrow.
 
Ok,
Try not to get in a hurry.
I would like you to locate the high speed and low speed air jet "tunnels" on the Inlet side of the carb. Looking at the mount flange for the intake housing or "muffler" as it's called....
At the top of that flange are the two openings. It's always good to hose them out with spray cleaner.

Also, find the brass tube that juts out into the carb throat. That's the accelerator pump tube. Following the path of that tube back inside the carb body and locate the passage that feeds it gasoline from the accelerator pump.
Use a small pocket screwdriver to prop open the throttle so that the plate is fully open and you can see through the carb throat from the rear. Locate the TINY jet at the end of the brass tube.
Using the straw that comes with the spray can, carefully cover that jet or nozzle with the end of the straw and see if you can get fluid to come out of the feed passage hole. If not, keep trying.
After a few tries, put fluid through the feed passage hole and see if fluid squirts out the nozzle in the tube.
But DO NOT look directly at the nozzle when doing this!

Ultimately, you want to see an 8 foot stream of cleaner shoot out the back of the carb from that nozzle.

Make sure the two vents on the top of the body will pass fluid to the float chamber.

If you haven't removed, inspected and cleaned the jet set tube yet or don't know what that is...
let me know.
 
Other things I should have asked you about are your remote control features. Is it a Honda control?
And is it properly wired to provide overheat warning and engine oil pressure?
Does the green oil light come on and stay on while it's running?

I asked you not to get in a hurry but I'm probably the worst at doing that.

For example, recently a guy had a "low power" issue and I was focusing on the carb because it's usually the culprit. Only to find out it was a bad kill switch that was trying to shut down the engine because of the normal vibrations occuring. Simply unhooking the ground to it had the engine running beautifully.
Those are little things to check out prior to ripping stuff apart and I'm guilty of often overlooking them.
 
It’s remotely controlled (throttle only) by a Trollmaster electronic dial unit I installed. The servo and control box all function as intended. Steering is via manual linkage to the boats outdrive.

Green light stays on for oil pressure while running.

Overheat wiring is something Ive never verified or had issue with (has never overheated in my limited use).

I did however see that timing looks to be off on first glance. 2 teeth off on TDC for cyl #1. To be clear, is there any chance that can be a slipped gear-on-camshaft position and still be running fine or did I just discover the high rpm issue?69E0AFBE-44D3-41B5-AD15-DDCC2456745E.jpeg
 
Well, it might not be the whole of the issue but I sure wouldn't run it anymore until that's been repaired. If the belt isn't bad and jumped on you I imagine it got that way by someone working on it and screwing up. I've never seen a problem with the cam pulley but ANYTHING is possible on a used outboard that people have been messing with. But, I haven't seen EVERYTHING yet, so who knows?

Good luck
 
It’s alive! I moved the timing gear back 2 teeth to the appropriate marks, adjusted throttle cable and reset idle to 900rpm. Oh boy is it awake now! Full throttle achieved! I feel like I got a new engine. Thanks for the help and encouragement to take my time and pay attention. Video to show the difference below.
 
That's great! Way to suss it out!
Really good that you caught that.
So much though for being able to put any faith in that shop you bought it from. Pretty typical in the outboard sales and service racket I'm afraid.

Now, feed her clean fuel, change the oil and filter, service the gear box and keep an efficient water pump on her and you will have what many Honda twin owners enjoy. A LIFETIME OUTBOARD!
Happy boating
 
Bye the bye...

Check out that belt and BOTH the crank pulley and cam pulley belt teeth for ANY signs of why that puppy got out of time.

The belt is just too cheap and easy to replace not to do it in order protect that engine. If there's ANY DOUBT, THROW IT OUT.

Like I said, my guess is that someone might have set it up wrong but, why were they there in the first place?

I did once work with a guy that was a very gifted mechanic and drag racer. He would advance the timing on a LAWN TRACTOR to eek out a couple of more horses. But most of we mere mortals shouldn't be dabbling in such witchcraft.
I will never really understand why someone will not do their homework and buy too small an outboard and THEN, go about moving heaven and earth trying to turn an 8hp into a 10hp!
But.....they do.....all the time!

Anyway, good job so far my friend.
 
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