Yamaha 9.9 outboard 2stroke running poorly

[mattyc]

Hello from the Abacos,

My 9.9 Yamaha outboard ( 2002 2stroke) is acting up. Basically it runs fine at idle, but as soon as the throttle is applied, it bogs down and has no power and just sort of blubbers along. Gas is good ( no water), I have cleaned the carb 3x, checked all the electrical connections including the grounds and changed the plugs. It has spark, fuel, and air???? Any suggestions?

[cfarrar]

When you say "cleaned the carb," what do you mean? Are you sure the jets aren't plugged? 'Cause the symptoms are typical of that condition.

[mattyc]

Had the jets out and checked for obstructions. All good.

[s/v Jedi]

I had that with a 2002 Mercury 15hp and it turned out to be coil(s) for spark that are NOT used at idle rpm, only when throttle opens in gear so that the engine must work. I know very little about these motors but your problem sounds exactly the same.

[mattyc]

That's interesting. My 9.9 has 2 coils, one for each plug. Would they both fail at the same time? I was leaning towards the CDI assembly, but what do I know ... I usually fail miserably on any electrical issue. How does one test a coil or a CDI unit?

[amytom]

Maybe the fuel pump? Sounds like its starving for gas.

[sea-bee]

I had similar symptoms on a big 4-cyl 2-stroke years ago. Turned out to be "power packs" (read coil) of which there was one per cylinder.

Diagnosing which one was the problem with the big motor, and the advise from the mechanic was this: run the motor while it is making the problem occur, and then immediately stop and pull the spark plugs, and the problem cylinder plug would be cool.

Better would be to try a gun thermometer. That might tell you whether the problem was electrical (and impacting one cyl only) or fuel (and impacting both).

Chris

[mattyc]

Gas is new, jets are not blocked, yes it has a CDI and 2 coils. A member mentioned changing out the diaphragms ... do you mean the diaphragm that sits at the stop of the carb under the steel plate? The only other diaphragm I'm aware of is in the fuel pump. What would be included in a carb rebuild kit? Keep those suggestions coming... I'm really curious to solve this mystery. I'm usually not bad with small engines, but this one has me stumped. I'm suspecting the CDI or the coils ... electricity... my nemesis. I'm anchored off Green Turtle Cay in the Abacos, and sadly it seems that any electrical parts will take 2-3 weeks to get if the local Yamaha dealer is correct. I have some friends coming down next week and I'm hoping to have a diagnosis by then and have them bring the needed parts. Is there a way to test the CDI and the coils? Thanks for all in input so far.

[s/v 'Faith']

This is going to sound like a weird question... Does it sound more quiet then normal?

If you mix the fuel a little rich over time, it is possible for the exhaust passages to get partially plugged and cause the problem you are having... You may notice to runs more quiet, and maybe even a little more smooth....

[s/v Jedi]

doesn't the dealer have a mechanic? They can test the coils.

[mattyc]

I would say the engine sounds as per usual on idle. As far as the dealer goes, they could probably test the coil, but I'm trying to solve this on my own. Dealer happens when I run up the white flag and surrender

[mattyc]

Hello everyone, I took the engine into Abaco Yacht Services in Green Turtle Cay this morning and Scott diagnosed the pulser coil as the problem, not putting out the required voltage of 9v, it was only putting out around 3v. Sadly, they don't have the part in stock so this couldn't be verified. The pulser coil sits under the flywheel and I'll need a flywheel puller to get at it. I went to boats.net to check out the part in question and noticed that there a couple of other electrical parts under the flywheel connected to the pulser coil which is causing me a bit of concern. My sister and family are coming down in 2 weeks and I was going to have them bring the parts, but if it turns out that the other electrical components are also involved, I'll be stuck with guests and no dingy. I will run this by Scott. I've been getting around in my inflatable kayak - not a solution for 4 people. Anyway, thanks for all the input and I will update as things progress. If anyone knows about pulser coils, I'm listening.

[s/v Jedi]

Originally Posted by mattyc

If anyone knows about pulser coils, I'm listening.

All I knew is that it was the coil that was probably to blame... I paid somebody to fix it with mine. Hope this works out for you so that you have a dinghy for the guests

[mattyc]

In Nassau now, and picked up my pulser coil. Off to the auto parts store to buy a flywheel puller. Does any know the correct bolt size/pitch/thread for the 3 bolts that fit the flywheel. I believe they are 6mm ????????????

[Oceanis 40]

Often you can loosen the nut on top of the flywheel a few threads till flush with the top of the thread. Place a large screw driver under the ring gear so you have firm leverage, keep applying force and give a couple of short sharp taps on the nut. The fly wheel will normally pop up. I am sure you have done this job already by now. I believe in checking basic problems first before jumps straight to coils, stators and CDIs etc. When a boat idles fine and starts to faint when you accelerate, I would recommend checking the spring and ball bearing in the fuel line quick couplings, they get hairs, plastic and pieces of rubber in also the fuel bulb can be taken apart and check the one way valves for the same. Then check filter. Then take the cover of the fuel pump and remove the diagphragm and hold up to the light. Often these are made out of a dicoloured (with age) stiff plastic which wears with dirt and gets tiny tears. Most 2 stroke fuel pumps work off the back pressure of the bottom carburettor. Hence work a little when they need little fuel but fail faster. They also make starting sometimes difficult.
After that it gets more difficult and expensive unless you have a spare coil. Often a coil gone will be an intermittent problem but not always. It goes fast, dies a few second and goes again. Stator and charging coils under the fly wheel often have an advance/retard arm. Sometimes due to grease drying out these seize. If you have one, you should check it can wiggle freely back and forth and only stopped by the linkage. If you take the linkage off, it should have full movement without resistance.

I am more familiar working on the larger HP 2 strokes than the babies though.