Yamaha 9.9 stalls at idle and low throttle - please advise

[romandesign]

Last season I had a problem with my 1989 Yamaha 9.9 4-stroke I bought with my Mac 26D 3 years ago. It became very unstable at idle and low throttle - sputtering and stalling unless I give it a little gas. Sometimes after starting and running for a while, then sailing, it would not want to start again, requiring a few tries and extra throttle until it started. It's used only a few hours in a season. It was fully serviced before I bought it ans insides look like new for the most part. I replaced the impeller when I bought it. Yesterday when I got it out of my basement where I stored it for the winter, I changed oil in upper and lower units, changed spark plugs, that didn't help. Please look at the video: you can see uneven detonation - it is shuddering neurotically, then after I put it to forward gear it becomes unstable and eventually stalls.
https://youtu.be/FbaIOq_eCIA

I bought carb cleaner spray and tried to clean carburetor that way - see video below, it was difficult not to let the engine stall and I could not do it continuously like instruction said, or the engine would stall for sure. I did it several times, using about half or more of the can. Look towards the end of the video (around 9 minute mark) - I still see some uneven shuddering but I let it run on lowest throttle with forward gear engaged for 10 minutes and it didn't stall. So it looks a bit better now, but I'm still not 100% sure if it's completely fine.

https://youtu.be/9Efj3aubeLU

So my question is: does it look normal to you? Or should I do something else? Should I try to adjust idle with the screw? Disassemble carburetor and manually clean it? Do anything else? Or is it OK as is?

My worry is that if I adjust idle to higher throttle - it would put a larger load on gears when switching to forward or reverse from neutral. Also when hoisting sail or reefing under motor I want as slow speed as possible, so increasing lowest throttle is not desirable. But I'm worried if while docking or maneuvering in tight situations the motor quits on me at the worst moment - I'm gonna be in trouble.

[paula_ke]

Fuel flow problem. These little engines have tiny jets. I'm sure you were careful winterizing but just to be sure:
Before putting engine away for winter:
1) Put gasoline stabilizer in the gas.
2) Shake up the engine to get stabilizer mixed.
3) Run the engine for 5 minutes or so.
4) Shut the gas line off and run the engine dry. (till it stops for lack of gas)
5) Drain the carb float valve holding well (one of the the tiny screws at the bottom of the float valve well).

Others may have some additional tricks to good winterizing.

Problems like this may be but not limited to:
1) Fuel line filter is clogged.
2) Low speed jet has been compromised by gasoline shellacking (by product of gas evaporation).

Problem with carb cleaner in a running engine is that you can't get the cleaner into the low speed jet (since you are throttling hard to keep engine running).
The way to properly clean a compromised carb is a tear down and carb cleaning of the parts especially low speed jet.

Just thought of another possibility: flooding. I ran across this with my DRZ400 motorcyle engine. Flooding can be caused by:
1) sticky or flooded float in float well
2) float valve pin cannot settle into float valve jet (how gas is regulated into the float valve well)
And for really crazy, the float valve jet usually is a brass fitting that is screwed or push fit into the carb body usually with an 'O' ring. The high alcohol content gas causes the 'O' ring to harden and stop doing it job (sealing off the gas line) causing the float valve well to flood and thus the engine flood. Don't ask me how I know this!!!


GL,

Captain Paula of the good ship AirWave

[opie]

http://macgregorsailors.com/phpBB/viewt ... =9&t=20498

see above link for good answers

[NiceAft]

I have a 2003 Mercury 6HP 4 stroke. What it took me years to realize is that if I ran it for fifteen minutes at a good speed, and did this every three weeks, the engine ran fine when the summer season came. Being outside of Philly meant cold winters. I solved the problem by filling a trash can with water, placing the motor in it (clamping it onto the can), and starting its every three weeks, all was good for the season. It just sits in that can through the winter, and I change the water every once and awhile. Be certain to feel the temperature of the water in the can when running the motor. You don’t want the water temperature in the can to get warm. I also am certain to put Sta-Bil in the fuel tank.

Ray

[miamistyle]

Small 4 strokes are known to have issues if not run on a regular basis.

I had so many problems with mine that I ended up trading it for an older 2 stroke. The opening on the carburetor on that motor is very tiny. Any little particle can get in there and clog it.

You also have the problem of ethanol in most gas you find. That can cause issues. My best suggestion is to get good at removing and cleaning the carb, or to know someone who can do it cheaply.

Good Luck.

[Tomfoolery]

So my question is: does it look normal to you? No, it does not. Or should I do something else? Should I try to adjust idle with the screw? If it has an idle mixture screw, sure, give it a whirl. But note where it is now, perhaps by closing it gently and counting the revolutions to do so, in order to put it back where it started. Disassemble carburetor and manually clean it? That would be my next move. Invest in a tin of carb cleaner with basket. Compressed air with blow gun would be a necessity here, IMO. Do anything else? Inspect the float and float needle, as previously mentioned. Or is it OK as is? If it runs well enough, then maybe it's ok to use, but I would put some effort into diagnosing and fixing that rough idle.

[Highlander]

If it,ll run at all try running a can of sea Foam thru the gas tank & see if it,ll clean it out

J

[Interim]

and a couple more ideas:

1) use good gas. I run 91 octane (in my area it is that, or 87). And I add SeaFoam to each tank. My Yamaha 9.9 uses so little fuel, that the extra cost per gallon is irrelevant.
2) does turning up the idle help? perhaps it is just set low.
3) if the engine was fully serviced before you got it, perhaps someone reset the timing wrong. One peg off can make a difference.

--john

[133bhp]

After having same (very common) problems, I always run dry and drain the float bowl on my 2.5hp 4 stroke. Leave fuel any length of time in there and they clog. idle jet is the worst. I can come back to them now, assured they will start. My 5hp, will behave for a few weeks untouched.

You can run for a few minutes, slowly keep trying to increase the revs to a ) to allow fuel to break down the fuel deposits. and b) create vacuum to dislodge.

failing that, You can put you hand on the intake to create bigger vacuum. someimtes clears it. esle, strip the carb.