Engine Still Running Hot

My problem is solved and thought I would take the time to post the resolution. cmariner32 was correct - once I switched the t-stat from a 160 to a 140 degree, it ran steady at around 170 as it did before the engine rebuild.

Mercruiser states my engine uses a 160 degree and that is what I ordered. But, I decided to look through my records and receipts for previous 100 hour services and found the previous mechanic installed a 140 degree t-stat for every service.

Thanks to all who replied.
 
with a 140 degree thermostat, shouldn't he be at about 150 degrees? I'm asking because every boat I ever had that was RWC with 140 degree thermostats ran at 150 by gauge and temp gun. I don't understand how a 160 degree thermostat would allow an engine to run at 195 degrees if all was well with the cooling system. I'd expect 175 to 180 degrees.
 
Having tested a few thermostats, the rated temp is when the therm STARTS to open, not fully open. It may take 5 or 15 degrees more to fully open.

Another thing to check, only because of the overheat. Make sure the flappers haven't broken up and/or partially blocked the exhaust system somewhere down the line. It can get stuck in the outdrive itself. Same for old pieces of the raw water impeller.

Also, do you have a thru-hull raw water pick-up as well as the drive water pick-up?
 
exactly Charlie, 5 to 15 degrees is 165 to 175 degrees, not 195. 195 degrees is too hot even with 160 degree stat. If I sit and watch my temp gauges as my engines warm up, they'll get to 175 then drop about 5 to 10 degrees and I know when the stat opened. I think there is another problem with the cooling system above. If he was running at 165 to 175 degrees with 140 degree thermostats before his overheat, he was running too hot long before he knew he had a problem. I think he still has the same problem.
 
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