Thunderstruck

My modified carb 500HP has developed higher oil temps on stbd motor. After tearing apart the entire raw water system, rodding out oil cooler, ps cooler and fresh water heat exchanger, checked the hose through the transom, changed raw water pump I have not lowered oil temp enough to be comfortable as compared to the port motor.

After reading an oil temp post in the drive section regarding oil tstat I took apart the remote oil filter mount and removed the oil tstat. I put the themostatic end in boiling water and nothing happened, the plunger did not move. Got frustrated and stuck the thermostatic end in the flame on the stove and the plunger popped out. BTW I had a severe leak in exhaust manifold earlier this summer with salt water getting past the rings and raising the oil level by 1" so my theory is that the oil tstat got some salt or corrosion in the plunger and stuck.

Question, what is the temp the plunger should fully deploy. Since the oil tstat plunger pushes out against the spring and ports more oil to the cooler as the temp gets hotter I would think that at 212F the plunger should be sticking all the way out. Especially since my port motor oil temps are 220 max. seems like the port motor oil tstat has been open by 220. Anyone have any experience with this?

I am going to replace the oil tstat anyway but I wanted get some info from the board for educational purposes.