Rapid temperature fluxuations

[Scotty]

I recently bought a 1998 Maxum 1900. The boat only had 43 hours on it. Long story short, the seller let the motor freeze. I bought a long block from Jasper motors and installed it. The pump is new and the motor temp. Shoots up and then I can hear water surge in the motor when the tstat finally opens. I have tried three tstats with the same problem. I pulled the tstat and it runs great, but the temp is too cool. I'm not sure what to do. Can anyone point me in the correct direction?

[pascavone]

either your raw water pump is not working, you have a hose on backwards or the thermostat is installed up side down.

if you have a serpentine belt, it might be looped wrong, and turning the water pump the wrong direction.

At least it runs.... that a start....

[shrew]

Hi Scotty!!! WElcome Aboard!!!!

Is this a Raw Water Cooled or Fresh Water Cooled (Closed Cooling system)? Does the temp guage rise and fall, rise and fall? I had a similar problem in a vehicle a few years ago because of an air pocket in the closed cooling system. The closed cooling system essentially had to be 'burped'. Not sure if it applies but I thought i'd give it a shot.