I was wondering if I should have a thermostat. I remove the thermostat housing to replace a gasket and nothing was there. I know cars, but when it comes to boats I am a newbie. Motors are 454's.

Need more info about the engine specs, but most likely they should have 140* tstats.

I talked with hardin marine today. The previous owner removed the circulation pump and installed a crossover tube, without a exhaust water bypass. He should have used a oil thermostat that bypasses cooler until oil reaches 180. I ordered new crossovers with t stats and oil stats.

I just added a thermostatless crossovers and got rid of my circulating pump to my engine. I noticed that I was starting to get some condensation in my valve covers. I just got some thermostat housings housing and started replumming.

Some problems you can get from not having T-stats are: hanging intake valves and condenstation in the oil.

I guess I don't know more than Mercury..........they put them in their for a reason. l am living and learning.