'93 Ski Nautique 351 PCM Pro Tech Overheating

And the best way to test either one is to suspend it in the water.If it sits on the bottom you will get a false reading due to the contact to the hotter bottom of the container.

I ordered a new 143F from SKIDIM today along with several other items and spoke extensively with Vince(great help). He indeed said it probably was a faulty thermo, but still could be a number of other things. I couldn't wait so I drove to Houston to pick one up from Palmer Power. I spoke a good long while with the manager there who also was very helpful. I showed him the old thermostat that I took out and he confirmed that it was a 160F. Remember in my previous post that when I found out the tech had installed a 160F I had him change it back out to the original 143F which he said he did. Obviously he LIED.
Well I got back home and immediately installed the new thermostat. Hooked up the water supply and started the boat the temp. rose to 140-150-160 all the while I had my hand on the top of the thermostat housing to see if I could tell a temp. change. At 165 I started to feel a difference, at 170 it stopped rising and dropped back down to 160 and stayed there. I let it run there at about 1,000 rpm for about 5 minutes feeling spots on the engine, checking water flow out the back. I felt safe to rev to about 1,500 with not much change. I decided to install my fresh water strainer back inline, had to go to local auto parts store to obtain new o-ring. I installed the strainer along with reconfiguring my water hookup. I this time used a 5 gallon bucket to let the water hose fill the bucket and let the motor pull the water from the bucket. With the bucket full and water running over I started the engine. Same result with the temps and felt good suction from the hose connected to the engine. At 1,000 rpm and water on all the way, the bucket would still run over. At about 1,500 the bucket would stay level with the top, at 2,000 the water level in the bucket starts to drop fairly quickly. I feel pretty confident I have solved the issue, but the true test will be getting it into the river(hopefully tomorrow evening, have to work). Another step I want to verify is test the engine areas with thermo gun(hopefull tomorrow or Thursday). On and by the way I still have yet to recieve a call back from the shop where the original service was done(imagine that).

Good to hear of your progress. Sometimes the cause is right in front of you, but mixed in with extraneous information.

Your boat looks great. Have you considered replacing the side graphics?

Will be replacing decals in the next couple weeks. One good thing about the whole process is how much I have learned about my boat. This is my first one.

Can't confirm anything what the original service tech did concerning stat replacement other than the 160F that I took out(it was installed correctly) which should have been a 143F. All I know is that when I replaced the 160F to the new one it seems to work like it should.