Runnin hot...bah!

[TheTinMan]

Pullin my hair out here. My 98 Merc 200 EFI gets an overheat alarm over 4000 rpm's. I replaced the waterpump, thermostats and the dealer did the poppet but still getting alarm >:(

I replaced a 15 psi water pressure gauge with a 30 psi one, 15 is too low for my motor. I also installed a Faria cylinder head temp gauge and sender.

I launched the boat today to run the Seafoam process....good stuff, try it! I needed to run the boat pretty hard after the Seafoam. Water pressure is WAY too high. The 30 psi gauge gets pinned at only 3000 rpm!

I did get her up to 50mph @ 5600 rpm ;).....and an alarm too! :'( :'( Temp gauge was only reading 145-150F. I really need one of those infra red thermometers that you just point and get a read on all cylinders to see if I'm actually running hot or not. Could just be a temp sensor maybe???

The really high pressure kind of points to the poppet valve not working properly. I have that pulled out and will take to the dealer tomorrow. If that doesn't fix the pressure problem I have a blockage somewhere. I'm hoping that's not the case because I really don't feel like pulling the power head and lower unit off.

Any Merc heads have any ideas? How bout you BigShrimpin?

Thanks