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2017 Yamaha F90 here. Boat has been sitting for a few months because of bad weather and lack of fishing time. Recently took it out, turns on fine, idles fine. Once accelerated to around 5000 RPM all of a sudden it drops speed and lowers to 4000 RPM, its stays like that for a few seconds, then it goes back to 5000 RPM without me touching the accelerator. It did it a few times on my way to the fishing grounds, then it stopped doing it and stood constantly at 5000 RPM, when it drops speed you can floor it all you want, it wont accelerate pass a certain speed, then all of a sudden it goes all the way up. After my fishing trip it did it on my way back, but way less times and way less deceleration. Water filter separator changed about six months ago, and fuel filter about a year ago, always used non ethanol gas.
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I feel your pain. Make sure the small filter on the back of the engine has gas and your fuel tank vent is open. -
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Are you sure it is fixed?
awful strange for 2 plugs go bad at the same time
have you run it much since replacing the plugs?Comment
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yep, two at the same time, things got worst, engine was running super rough at idle ( something it did not do at the beginning) one cylinder was not working at all and the other one was really bad, we switched injectors but the problem kept on going on the same cylinder, so we tought it was the spark plugs, so we swtiched all four ( i already had them bought before) and problem solved.Comment
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need to find out what caused the failures of those plugs.
Something contaminating them could be the problem, like salt waterComment
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funny thing is they did not look bad just by looking at them.Comment
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I had the same issue with my F150 years ago, but not quite as bad.
Super low hours on the engine...Shop said the plugs should be changed (which looked brand new)
Installed new plugs, fixed it...Scott
1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXRComment
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