Trojan Boat Forum

140 raw water cooled 180 fresh water cooled ( uses coolant ) .







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If it's a raw water cooled unit, you should be using the lower temp stat. If it's closed cooling (fresh water cooled, has coolant and heat exchanger), It's likely you have the higher temp stat. You must confirm the one you have as the temp cut off switch spec is dependent on the stat used.

Hey, stop writing at the same time as me.....what he said

mine is lake cooled and uses 140 same as Chrysler engines. Bob at Beacon explained that the higher temp t stats would cause adverse reaction with salt water in the engine so the 160 to 180 are fresh water (antifreeze in raw water heat exchanger) at least with Chryslers. bet same for gennys.

larryeddington wrote:mine is lake cooled and uses 140 same as Chrysler engines. Bob at Beacon explained that the higher temp t stats would cause adverse reaction with salt water in the engine so the 160 to 180 are fresh water (antifreeze in raw water heat exchanger) at least with Chryslers. bet same for gennys.

Thanks! that is what I was thinking. Use 140* for Mississippi cooled. This one had 180* stats that were plugged up. Go figure, no strainer either. Correcting that too.
Thanks everyone for setting me straight!

larryeddington wrote:.....the higher temp t stats would cause adverse reaction with salt water.....

The concern is that higher temps increase the rate of salt depositing on all surfaces it comes in contact with and it also promotes crystalline bridging. In a short time, it would cake up the inside of the block and cooling system components. The fix, or at least the way to prevent deposits from forming as quickly is to run at a lower temp however running a cooler engine has it's own set of drawbacks.

Big D wrote:

larryeddington wrote:.....the higher temp t stats would cause adverse reaction with salt water.....

The concern is that higher temps increase the rate of salt depositing on all surfaces it comes in contact with and it also promotes crystalline bridging. In a short time, it would cake up the inside of the block and cooling system components. The fix, or at least the way to prevent deposits from forming as quickly is to run at a lower temp however running a cooler engine has it's own set of drawbacks.

What are the drawbacks of running a cooler engine? I don't believe my boat has a thermostat in it since the hottest it seems to get is 105F. I replaced the gauge and sender, so I know the temperature reading is correct.

The Dog House wrote:....What are the drawbacks of running a cooler engine? I don't believe my boat has a thermostat in it since the hottest it seems to get is 105F. I replaced the gauge and sender, so I know the temperature reading is correct.

Engines are designed to operate most efficiently within a window of operating temps. Low temps increases fuel consumption, and they don’t promote burning off moisture in the oil. Water in the oil combined with combustion by-products produce acids harmful to engine components. Oils and their lubricating properties are designed to be most effective within normal engine temp specs, so are the oil filters. Cold running prevents proper expansion of engine components like pistons, rings, etc. which is needed to bring clearances to normal spec while running to promote proper combustion and minimize component ware. Seals are also designed to run at normal temps and become more effective at such. Cool temps also cause higher soot levels and fuel dilution,…... 140 degrees for raw water cooled is already too low but necessary for other reasons so lower than that is not good. If you can’t get your engine to proper operating temp, I wouldn’t run it hard!

Draw backs of running to cool ? You will burn more fuel .It won't run as efficiently Your will end up with more moisture in the oil . And things break a lot easier . I can't remember how many valve springs I have seen break on marine engines . In every case of these broken springs ,I found the thermostats were removed. I also help replace a diesel that threw a rod that was run up cold (rod shattered ) Can say for sure that was the cause but can't rule it out 30K+ later you can bet he will let it come up to temp from now on .

On some engines the thermostat closes a bypass when open . removing the thermostat on them can cause a over heating condition .

Big D you trying to get even by posting while I am typing ?

What big D said X2 I think we are on the same page

I had to improve my typing speed because of you

Dam Canadian short hand !!! ITS Not fair I tell you !


I have got to get faster thumbs

Any idea where I could purchase a 140F thermostat for a 1971 Chrysler 318? Beacon Marine is sold out.

They are available, just google them. I did some extensive work on my 6.5 and found a defunct dealer that had a lot of parts. Do a search on my posts for Onan, I believe I posted it there.