Alarm sounds on plane only why 1995 40hp

[Streamln1]

Help does anyone know why on a 40 hp yamaha 1995. Impeller,thermostat,fuel oil mixed in tank, head plate taken off and acid bath around cylinder heads, poppet valve ok, water flow good and slightly warm.


I really am puzzled also engine has no VRO.

HELP.

[Aleutianwest]

buzzer

check intake grates on lowerunit make sure not backwards or plugged

[Streamln1]

Can anyone help figure this out

yes did that to also took off the lower unit and double checked that the impeller was install properly. Also, I removed the thermostat and poppet valve and still that buzzer sounds?

[jb123]

so instead of replacing the 16 yr old parts you just take them out and expect the motor to run correctly ?

when I have overheat issues i replace everything... cheap insurance....but thats just me

[99yam40]

All water cooled motors have to have a restriction in the system to make sure the water circulates properly to all parts of the motor. Removing the thermostat will cause hot spots and over heating in those areas that do not get the proper circulation. Put the thermostat back in but make sure it functions properly by testing it.
I did not think that motor had a PRV or poppet valve, so I have no idea what you pulled out

You can pull an test the temperature alarm switch to make sure it is funtioning properly in a pot of water while heating and monitoring to see at what temp it closes and reopens to see if it is in spec.
If it is then you are having a over heat problem

[Streamln1]

is it possible that the exhaust from the cylinder is blowing hot air past the gasket and over heating the water. I tried every combination I can.