When you're putting an engine in a boat for the first time how do you determine if you should be using a thermostat or not? Seems like you need to know this up front so you can buy the correct parts to run one if needed. This would be for a NA 540 making 650 hp in lake erie. Thanks

I was researching this recently, lots of opinions.. I found the general consensus was to use one on a N/A motor, I have similar power as you 557 N/A motors & I run 140's - the gauges read 150 while cruising, Blower App is another story - you want them to run as cold as possible

Assuming you know what temp you want to run how would you know if you would require a Thermostat to hit the temp prior to running the engine in the boat? If you're buying a crossover and housing how do you know if you should get one that has the bypass? Can you just guess that if its a na motor that it should run a thermostat?

I dont run a thermo, blocks run about 110 after warm-up/ but I run thermo oil coolers, set at 180. The shop that build motors said to keep the water pressure lower at high rpms to not use the thermos. The setup works great. 540cu merlin tall decks, huber trans, arneson drives.