Alarm going off, assuming overheat???150 yamaha

[Richardsonracing]

I have a 1996 yamaha 150hp V6-2596cm3

Alarm first started when cruising across the lake at full speed. As soon as alarm went off it went into rpm protection mode. After killing it and letting it cool off I was able to restart with no alarm. If I went slow I could go a ways, but the more rpm's the faster the heat and faster the alarm. Now i can just start it and let it idle for about 3 minutes and alarm goes off. The impeller pump has been changed since and tonight I tested the thermostats which seem to be working just fine. This boat does not have an oil pump as it's self mixing. Where do I go from here to figure out the reason for the alarm????? Thanks in advance!!!!!!!!!

Ron

[boats.net]

Start at the water pump, housing or impeller could be be bad. Check pressure control valve is not stuck open.

[Richardsonracing]

New water pump installed and boat pees fine. I checked both thermostats and they are working fine. Next I took off plate for pressure release valve and the plastic piece that goes inside the rubber washer was very tight and hard to turn or pull out. It seems as corrosion build up got underneath the rubber o ring making the tolerances too tight for the plastic piece , sorry not sure what it's called, making it tight. Now I have a different prob. I knocked the rubber seal into the motor. I reinstalled everything without it and with it still inside motor. So far no overheat alarm, I'm only running it in driveway with muffs. I know I have to get it out! Any suggestions on how? Thanks!!!

[Oxander]

same issue it was the oil system port

after doing a total rebuild after this issue my mechanic told me to just put the oil in the gas as the oil injection system does not always work well and eventually fails. I have been running it this way for a year now no issues.

[Richardsonracing]

Well, took the boat out and it ran the best it has in a long time. Problem is now the motor isn't "pissing" but I got rid of the over heat alarm. Looks like a stuck poppet valve was my problem. Now to figure out why it's not pissing and how to get the seal from the poppet valve out of the motor. Any thoughts...