02-200 hpdi. temp alarm goes off every now and then and i've got 15-20 lb on the gauge and peeing good. impeller is 4-5 yrs old, but pressure is great, sooooo------? first time it went off i thought it was a low oil alarm, but got plenty oil. next time i looked at the gauge and the temp indicator is blinking. let it sit 4-5 min and everything is fine. this motor is driving me crazy. i've got 995 hrs on it and never had a mechanical problem, but the fuel problems are leg
endary. now temp problems---aaaarrrggghhh! i did catch a couple reds and a flounder though!

That's too long on an impeller. I would do a complete cooling system service including poppet assembly, thermostats and complete water pump.

why would the impeller be bad if i'm getting 20 psi?

I agree with this...it's a good thing to do anyway for preventive maintenance & peace of mind. Sometimes small pieces of the impeller break off and restrict the cooling passage. Don't ask me to tell you how I know.

Question is how much pressure do you have with a new water pump? Should be close to 30psi at WOT. Is your water pressure gauge right?

Gary, i've been rearranging the wiring in the console and i rerouted the water pressure line. before that i always had 25-30 lb at close to WOT. afterwards, it was 15-20. i assumed that when i cut the line and shortened it, i left about 1/8" sticking out of the ferrel at the guage, that it was a little compressed and not showing as high as before. hard to believe the water pressure would change overnight.
today, if the weather allows, i'll take the boat out of the water and replace the pump and both thermostats and check the temp sensor. after all the work i've done to the boat this winter, it's killin me that now i'm hav ing these problems. thanks for you help.
after some more research, looks like i might as well do the poppit valve also.

More than likely the pressure relief valve "poppit" is stuck open not allowing water to get to the top end where the thermostats are, went through the same thing with mine last year. But would be a good idea to flushed and impeller replaced.

This.

You should be running around 30-35 psi. You better change that pump before your next trip or you will be replacing the motor soon. 15-20 is way to low.

I change my impeller every two years! Cheap fix/insurance.

WOW.----waiting on weather.