Alarm at high revs

[Desperate Demetri]

I have a 1988 V6 Excel 225 hp Yamaha Outboard. It runs great up to about 4200 RPM. At higher RPM (4500-5500), it will run of for approximately 5 minutes. At that time an alarm sounds (steady alarm) and the motor starts shutting down. After 2-3 minutes turned off, the alarm goes away and all is normal until it is pushed at the higher RPM again. I am fairly certain it is not overheating because the cylinder heads are not too hot to touch. Also, I have replaced all thermostats and the water pump impeller and I can run at 3900 RPM for extended periods of time without incident. Finally, the oil reservoir on the engine appears to be at a normal level. Any suggestions?? Restricted oil flow? Bad Oxygen sensor? Faulty or dirty oil pump? Thanks in advance for any info.<br />DD

 

[bossee]

Re: Alarm at high revs

Hi,<br />Check in your outboard manual what a steady alarm is supposed to mean. Any warning lamps that flashes in any guage? I had a Suzuki DT65 before (I have a Yamaha F115 now) that had trouble with alarm going "on". After much investigation it was found out it was the heat sensor that was defect and when it was replace with a new all was fine. The overheat alarm only kicked in at higher rpm, so it is somewhat similar to your situation.<br />But before that was found to be the cause I had replaced impeller with a new, also a new thermostat and cleaned the cooling channels. If overheating is the problem with our outboard I do not know. Also there is a revlimiter that kicks in at over rev but it seems not your outboard is over rev?<br />Good luck.

 

[rodbolt]

Re: Alarm at high revs

+hello<br />well after testing the over heat sensors then stand by to remove the heads and replace the gaskets. you describe a classic combustion gas leak into the cooling system.

 

[rodbolt]

Re: Alarm at high revs

hello again<br /> low oil in the engine oil tank will cause the steady sound as well. do you have any alarms visual indicators ?

 

[BRIAN03]

Re: Alarm at high revs

Hi The 220 special doesnt have an o2 sensor. There are two reasons that engine will go in rpm reduction. The first is high heat or low oil on the oil tank on the engine. The engine might not be getting hot it may be one of the two sensors on the cylinder heads (pink wire and black wire). When the alarm sounds remove one pink wire at atime untill the alarm stops. On that engine the oil tank alarm wire is also connected to the alarm cicuit on the cylinder heads. Look behind the tank on the engine and you will see the pink wire. If the heat sensors on the heads dont turn the alarm out disconnnect the pink wire on the oil tank on the engine.If that does it and the tank is full of oil you need a new tank sensor. 130.00 us.