2002 40 HP Yamaha Tiller Problems

Hello –

I just got my boat in the water today and my 40 HP Yahmaha Tiller was not running very good. It seems to idle fine in neutral – although seems to vibrate/run a little rough. When I put it in gear and give it gas it doesn’t really respond and if it does the motor quits within seconds. I had the carbs cleaned 2 years ago and then they did it again last fall(said they did) because I said I wasn’t happy with how it was running after they were cleaned the first time. It was also “professionally” winterized last year. Wishful thinking on my end is it’s bad gas. Any other ideas you guys have? I do think I am done with the current repair shop as I think they should have it running smooth after 2 cleanings, 2 winterizings, and me describing the problem? Any other ideas what the problem could be?Thanks in advance.

Chad

Fuel filter or a bad gas line/bulb would be my first two choices.You can eliminate the gas problem by getting rid of the old stuff,(lawm mowers seem to like it), and buy some 92 octane.Try it,if it works then you know it was the fuel…

Try dropping down to 87-89, it makes my motor run a ton better than the higher stuff.

Have you checked the plugs?

Do you have a small tank you can run the motor off of, with fresh gas? Dont just add new gas to the old, start with fresh.

When I had my 40 hp Yammie 2 stroke I was having troubles with it running rough, not idling good and they recommended using Stabil Marine treatment regularly and that did the trick for me – luckily. It’s no fun having troubles with motors and not getting satisfaction from repairs. Good Luck.

Make sure all hose to carb are ok no cracks and fuel line hose is in good shape. Sucking air in from a crack hose will cause poor running at higher rpm’s. When I have my engines work on I always have them run engine in front of me to make damn sure they are runnning smooth. Good luck!!

ADD Seafoam to the gas..sounds like a water problem to me, wasn’t treated at winterization….if you want it done right you have to do it yourself..

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ADD Seafoam to the gas..sounds like a water problem to me, wasn’t treated at winterization….if you want it done right you have to do it yourself..

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You didn’t say if is a 2 or 4 stroke. Mixed gas can form a sludge that very easily plugs the low speed jets which is what is happening to you. Aside from tearing it down and reaming the jet with a wire plucked out of a wire brush (A trick I learned from Mr. Holst) Sea foam is a great first step. I was able to fix my weed whip and auger with Seafoam. It simply works.

You didn’t say if is a 2 or 4 stroke.

Sorry, it is a 4 stroke.

Mine absolutely hates old gas. Or water in the gas tank. Or a loose battery cable.

My dad has had this same problem with his brand new 30 hp etec. He bought it last year, and our first time out in the water (middle of nowhere in canada) it would just idle down after he put it in gear. He tried to get it fixed over the winter, so we took it to the mississippi a couple of weeks ago to see if it worked, but it didnt. He again took it to a marine shop and we just got news yesterday that it kept overheating because not enough water was getting through it. Check the water hose and ask a dealer if you think it needs to get replaced.

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ADD Seafoam to the gas..sounds like a water problem to me, wasn’t treated at winterization….if you want it done right you have to do it yourself..

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Seafoam is a fuel system cleaner. It cannot and does not remove water from gasoline. If the gas is contaminated with enough water to cause engine problems, then only a mechanical separator can remove it.

I’d check the plugs, clean them and check for proper plug type and gap. Also, make sure the plug wires are on the correct plug.

As others have mentioned, check the fuel hose both external and under the cowling. Replaced any hoses that show any signs of cracking.

If there is a fuel filter (and I think most late model Yamahas have them) then replace it.

Pump about a quart of fuel out of the tank into a glass jar and check for water contamination. If the contamination is significant enough to cause the problems you are experiencing, you WILL be able to see it when you pull a sample. If you don’t know what to look for, just ask.

BTW, fuel that’s contaminated with water can be treated pretty easily. In aviation we used to use a device called a “chamois funnel”, although I don’t believe they actually use a chamois anymore. Bottom line is that this device takes advantage of the density differences between fuel and water to stop the water from passing through.

West marine now carries the modern version of this separation funnel. Pump the wet gas out of the boat, though the separator funnel, and into cans. Then either burn in a car or return to the boat. I think the funnel costs less than $20.

Grouse

Did you just hook up a hose and run it that way or did you take it out? Most of the time they spray the carbs when they winterize it and might take a little bit of time for that to work itself out. Is it fresh gas you are using. If you dont have a fuel water separator filter that is the first thing I would add. If it still runs rough spray the intake with carb cleaner.