Boat thermostats

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5,149
Location
South Carolina
... It's about the worry of salt crystallizing in the cooling passages.
^^^ This ^^^

and ... its important to remember, water temperatures are not oil temperatures. Marine oil temperatures run far hotter then the water temperature.
This goes for any vehicle, but way more so in marine engines that run under incredible stress pushing a boat though water vs a vehicle with wheels.
Throw in the high RPMs, stress factor, bearing heat, super hot pistons getting cooled with oil being sprayed on them and I am sure your oil is much hotter then a automoble running at a higher water temperature then a boat.
Plus its in an enclosed space. Water temperature is not oil temperature. I think many would be surprised if they check oil temperature.
Two different fluids, doesnt make sense to talk about the temperature of oil by taking readings of the temperature of the water anymore then it would to talk about the temperature of the water by taking an oil temperature reading.

BTW my Volvo engine is spec'd for 20w50 oil
 
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Messages
2,056
Location
Minnesota
^^^ This ^^^

and ... its important to remember, water temperatures are not oil temperatures. Marine oil temperatures run far hotter then the water temperature.
This goes for any vehicle, but way more so in marine engines that run under incredible stress pushing a boat though water vs a vehicle with wheels.
Throw in the high RPMs, stress factor, bearing heat, super hot pistons getting cooled with oil being sprayed on them and I am sure your oil is much hotter then a automoble running at a higher water temperature then a boat.
Plus its in an enclosed space. Water temperature is not oil temperature. I think many would be surprised if they check oil temperature.
Two different fluids, doesnt make sense to talk about the temperature of oil by taking readings of the temperature of the water anymore then it would to talk about the temperature of the water by taking an oil temperature reading.

BTW my Volvo engine is spec'd for 20w50 oil
marine engine oil temperatures are very close to the same as automobile engine oil temperatures. Most marine engines are based on car engines. This has been well studied because oil breaks own in the 240 degree range.
 
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5,149
Location
South Carolina
marine engine oil temperatures are very close to the same as automobile engine oil temperatures. Most marine engines are based on car engines. This has been well studied because oil breaks own in the 240 degree range.


I said nothing about automobile engine oil temperatures being different then marine engine oil temperatures, though I think you will find higher temperatures if you measure your boat with a car after a 1 to 2 hour run, you misread my post and that's ok, just letting you know as others might be mislead..
Oil does not break down at 240 degrees but will agree once you get to the 250 to 270 range it will degrade some, I guess, but have not really seen that happen in my Harley though I do change the oil sooner rather than later.
 
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2,761
Location
Caldwell Idaho
The cooler temps is as mention for deposit control with raw water cooling. I have built several boat engines over the years and the piston and piston ring manufactures have different clearances for a raw water cooled marine operation.
 
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25,966
Location
Upstate NY
Back in my day fresh (raw) water cooled engines ran a 160 thermostat and closed systems ran a 180. Closed systems were easier to control. Raw water systems running in the Tropics (or in a nuke plant cooling lake) might start out with a much higher water temp. Also, closed systems were much more efficient.
+1 - its all about fresh water cooled engines or raw water cooled engines.
 
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