'02 150 vmax overheat alarm. advice please

[deslinger]

Ok folks, thanks in advance. please read all.

Recently purchased 02 lowe Tahiti with Yami 150 vmax. First trip made a sharp turn and got a overheat. Idled down and alarm went off. next trip WOT about 5500 rpms got alarm. waited awhile to allow cool, ran all day without another issue. thought for sure was sticking thermostat. yesterday replaced both thermostats and impeller. Went out again and again at WOT got alarm. was playing with the trim and thought maybe cavitated. allowed it to cool again and after a run at WOT got another alarm. Shut down to allow cool and noticed white "smoke" coming from exhaust ports at the same moment I shut it off. waited and started motor while alarm was sounding. the temperature of the pee was exactly the same as lake temperature.
After it cooled I throttled down to 5000 rpm's and ran it another hour without issue. Today checked pressure relief valve. minimum buildup but I also noticed yesterday after the second overheat water was coming from the exhaust ports.
Any thoughts on what to check or do to troubleshoot? BTW. motor never went into limp mode.

[deslinger]

Oh also.... Alarm was solid and constant. I called my mechanic from the lake on the second trip. he said continual means overheat and beep is oil.

[boscoe99]

Let's see here. An alarm goes "off" and that means trouble. But then, the alarm goes "off" and that is good.

This is not directed at you. It is directed at folks that say might their alarm went "off", what needs to be replaced, when really they mean that their alarm turn on.

First, you need another mechanic. A Yamaha sounds only one alarm. A solid tone. Could be over temperature or could be oil system related or could be a fault in the alarm system. But the alarm is the same. Your mechanic might think that you have a Mercury motor.

Another reason that you might need a another, but better, mechanic, is because when the alarm is activated the motor is supposed to go into RPM reduction mode, which you are saying did not happen. That needs to be fixed.

Did you replace just the impeller or did you replace the entire pump, to include the base plate? What does the water flow to the motor look like when you are running it at high power?

By the way, pee water will always be more or less lake water/sea water temperature. Generally, just a tad higher. Water out of the tell tale has not gone through the block. Again, someone is confusing a Yamaha with a Mercury.

[deslinger]

Thanks for the reply

Ok. point taken on the alarm went "off", but you do understand right? lol

My mechanic has not looked at this motor to be fair to him. we only had a conversation on the phone. The white smoke or steam would indicate a temperature issue though. In fact I thought at first I had a blowed head gasket but the compression test was good.

Only replaced impellor. everything else looked good and I have lots of water flow out the pee hole. even when it got hot.

As for the info on the temperature of the water out the pee hole, thanks for the info. that was only my observation at the time so I included the info here.

[rodbolt17]

like its been said, SAME TONE for ALL alarms.

could be battery voltage,water in the fuel detect,low oil level in the engine tank.
could be a chafed wire.
and like its been pointed out,the ECU controls the horn ground path.
anything that sets the alarm also sets RPM reduction, except water detect on that model.
its supposed to but doesn't always.
what gauge package do you have???

Yamaha digital or aftermarket?

[99yam40]

anything that sets the alarm also sets RPM reduction, except water detect on that model.
its supposed to but doesn't always.
what gauge package do you have???

Yamaha digital or aftermarket?

Seems like that would be where to look first if you have not already