Yamaha 90hp problem...Help

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ahifever

Cadet
Joined
Jun 28, 2005
Messages
19
I have twin 1986 90etlj and I recently installed a new impeller on one of them. I went out for the first time since installing it and after about a minute of running under load the rpm's would drop and pulse between 2500-2800. It would not rev higher but would run smoothly below those rpm's, I'm thinking its some kind of overheating problem? maybe temp sensor? Please, any advice would be appreciated. Also, where is the temp sensor located? I loaned out my manual and haven't got it back yet.
 
R

robards

Seaman Apprentice
Joined
Apr 20, 2002
Messages
34
Re: Yamaha 90hp problem...Help

Could be an overheat problem since it didn't do this prior. I would want to pull it down and make sure the install is correct and the pick-up tube is in the housing. Is the motor pumping and strong.
 
A

ahifever

Cadet
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Jun 28, 2005
Messages
19
Re: Yamaha 90hp problem...Help

robards,<br /> thanks for replying, I dont think its an overheat problem anymore, as I changed everything <br />that could cause it and yes It is pumping strong.<br />I'm starting to think its electrical, maybe coils or something. I went out on the water to run it under load and it will get to about 2500 rpms and the whole engine starts to shake. Revs to about 3000 then cuts out down to 2500 and pulses like that throughout.<br /><br /> Maybe one or two cylinders not firing? I am going to change out all the coils and see if that works. Any other input would be appreciated.<br /><br />Thank you <br />Ikaika
 
B

bigbrownbuku

Master Chief Petty Officer
Joined
Sep 17, 2004
Messages
885
Re: Yamaha 90hp problem...Help

check the spark. if you have 3 sparks it wont likely be the coils. it would seem your motor is going into a "safe mode". does an alarm sound? does the alarm even work? to test the alarm locate the temp switch on the cylinder head, disconnect it and plug the 2 wires together or ground out the pink wire.
 
A

ahifever

Cadet
Joined
Jun 28, 2005
Messages
19
Re: Yamaha 90hp problem...Help

BenC <br /> I think your right, it seems like safe mode or could it be a rev limiter? it almost seems like its red lining at 2500-3000 rpms. The funny thing is it will run good throughout the rpm range for maybe 30 seconds to a minute or so and then just pulsate at 2500-3000 after it warms up a little.<br /><br />I'll try to see if the alarm works.
 
A

ahifever

Cadet
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Jun 28, 2005
Messages
19
Re: Yamaha 90hp problem...Help

I checked the alarm and it is not working, but I <br />know that it is not overheating and probably not oil related. When I removed the tubing going into the oil pump? the oil was flowing out. I'm <br />stuck, what else could it be?<br /><br />Thanks
 
A

ahifever

Cadet
Joined
Jun 28, 2005
Messages
19
Re: Yamaha 90hp problem...Help

I think I fixed it! It runs great with the muffs but I'll have to wait till I take her out to know for sure. After everything I went thru can you believe it was the main ground power cable. <br /><br />BUT, now a couple more problems that just started after fixing the ground. Tach not working and the engine won't shut off when I turn the key off.<br />Whats up? Thanks in advance.<br /><br />Ikaika
 
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