Seeking advice on what could be my trouble with my 40 H.P Yamaha four stroke. She’s always been a little cold blooded but as of lately it takes 8 or 9 times to turn her over and then she’s coughing, vibrating and shimying until she warms up a little. I changed the plugs and the fuel filter. If anyone else has had experience with this or wishes to chime in any advice, please do.
Thanks in advance!
You may want to run a can of sea foam through it once in a while.
Yamaha carbs seem to gum up easy.
My mom has the same engine and about this time of year it does the same thing. They are cold blooded, but a can of seam foam usually clears hers up.
I can say I havn’t had a single hicup with my 75hp one. It starts with just a touch of the key everytime. I’ve never had to bump the throttle in iddle once even in February? I’ve got several friends that run Yammy’s and none have ever had a problems like the one you describe. They run motors from 25hp to 200hp ones. I’d say run a can of Sea Foam through it, but I’d take it in and see what the problem is. What year is it? Is it still under warranty?
Did it just all of a sudden one day after a fill up start acting up? Cause I have had similiar problems with an outboard and the results were it had watered down gas. Always fill up at gas stations you know. I filled up at some old run down station and the damage there fuel caused cost me.
A guy told me to drain out each bowl on all three carbs (brass screw at the bottom of each carb) so I did that, poored the ol’ gas from the tank into the lawn mower,old truck and empty gas cans. Added the sea foam to the new gas and she seems to be much better. I guess the carbs must have either had some moisture in them or I got bad gas…… I noticed in another posts and other forums that some guys are talking about bad gas and ethanol in gas hurting their carbs. Should I be buying 92 octane for the four stroke?
You mainly wanna run what ever octane the manufacturer recommends, running a different octane does not do anything to change ones horsepower,etc. The manufacturer has configured what that motor runs best on and that is what they recommend. Just keep using seafoam every now and then and you should be running alot cleaner… 
I would not run the high octane. It gets a higher octane from more ethanol. 
Seafoam, and Yamaha makes a de-carbonizer additive that is highly recommended as well from time to time.
The owners manuals state that up to 10% ethanol is not a problem. Does anyone know the effects of more ethanol??
I think the law makers were talking about boosting that to 20% across the state.
Run 87 in your four stroke.
I just talked to my moms mechanic about her 40 HP and he said she has a pin that sticks and that by pumping the ball extremely hard sometimes that can get it to break lose. He said it is a common problem with the 40 for some reason. Sounds like it is more common if it is not used for a couple weeks in high heat. Hers is being fixed right now. Sea foam or OMC 2 + 4 are always good to run in your gas though.
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