175 Yamaha with hot alarm.

[Hunterhja]

I have a 1997 Yamaha 175. Lately I've been getting a hot alarm when I run 35-40 mph. It will run all day at 30 mph with no alarm. Top end is 65 mph. My pressure gauge does funny while running. At idle speed it may show 3-4 psi or nothing. At higher speeds it may start with 20 psi then drop to 12 psi at the snap of your fingers. Pressure may drop just as fast to 8 psi. Pressure will continue to vary constantly 8-10 psi to 18-20 psi at the snap of your fingers. I did install a new water pump kit and new housing. This did nothing for my problem. I got this motor new and has never been in salt water. Any advice would be deeply appreciated. Thanks.

[zenoahphobic]

I have a 1997 Yamaha 175. Lately I've been getting a hot alarm when I run 35-40 mph. It will run all day at 30 mph with no alarm. Top end is 65 mph. My pressure gauge does funny while running. At idle speed it may show 3-4 psi or nothing. At higher speeds it may start with 20 psi then drop to 12 psi at the snap of your fingers. Pressure may drop just as fast to 8 psi. Pressure will continue to vary constantly 8-10 psi to 18-20 psi at the snap of your fingers. I did install a new water pump kit and new housing. This did nothing for my problem. I got this motor new and has never been in salt water. Any advice would be deeply appreciated. Thanks.

Checked your thermostats? They would not cause change "at the snap of the fingers" timeframe though. Nor would a faulty pump. A moving lump blockage might, but sounds too sudden a change. If you did not have a hot alarm I would have said your gauge is faulty or playing up with a blockage of sort to it. Thermostats a good place to look to get an indication of general corrosion in your cooling passage also.

And do you flush the engine regulary, even though you never use it in salt water? Weed and mud could be slugging up your motor's cooling passages. Give that also a go, and flush whatever line you have to your gauge also if nowhere else to go.