Yamaha 90hp outboard

[YamahaTom]

Im new to this forum but looks very informative. I had a question to ask you. I have a yamaha 90hp runs like a dream sips gas. its perfect. occasionally i have this problem where the motor will shut down after WOT to 2000rpm and will not go any faster but if you trim the motor up it will WOT but when its in the water ....bogs very bad. Im thinking an oil sensor? now its got to the point where the motor wont idle without knocking and hissing. Otherwise it will get up and scream on this aluminum boat.
thx for your help.

[robert graham]

Oiling system problems or overheating can cause motor go into RPM reduction mode to try and protect motor. Maybe check out both these systems for problems. Good luck!

[YamahaTom]

i know the motor has a good water stream...always does.. it shoots it like 3 feet...and powerhead doesnt feel warm...its very cool. where is the oil sensor located? i get lights saying the oil is low??? but i always always check the oil tank before I start it at the ramp.......and before I leave home. so 2 checks..for oil level.........

I think its a sensor its acting electrical?

[99yam40]

Does your boat and motor have 2 tanks or just the one on the motor?
We have no idea how old of a motor you have or what all has been done to it over the time you have owned it. Can you give us a little more info

[YamahaTom]

just one oil tank on the motor....the motor is old....at least 15-18 years....its a 2 stroke yamaha 90hp...(square cover) .....


I have a green circle on my indicator its a 3/4 full green circle....other than that...its just a tach...and a tilt trim indicator...and theres a horn underneath....the green light always stays on.......i always have the oil tank full of quicksilver

what else would you need to know?

[YamahaTom]

1984-1995 yamaha 90hp Precision Blend 2 stroke

[YamahaTom]

the other night ...i went out fishing.......i hammered down on the throttle......no problem......it planed out like usual and we were well on our way...

on the way back........i hammered down planed down and was going about a mile before the engine bogged down tremendously and wouldnt get to any RPM past 2000........no horn or anything alarmed....ill tell you that the horn used to alarm when i tilted up the engine and the key was on ...(engine not running) also at the time when it bogged.....i checked the oil.....it was full.....the engine had a steady water stream......i feel that its an oil injection problem. there was a little green light on the indicator panel saying 3/4 full....but it always stays on....

[YamahaTom]

could oil sensor or bad CDI unit be the cause of the 2000 rpm limit?

[calveryc]

If the green light is on thats a good thing, The red light is bad and the red light is worse. Read through the document below and see if it helps any. The reduction of RPM's could be a faulty sensor or it may think its overheating. The document below will tell you how to check out your sensor and lamp assembly.