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318 Thermostat

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stuart

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I own a 1973 F31 Trojan with 3

I own a 1973 F31 Trojan with 318 Chryslers and my problem is that both my engines will not heat up.
I have checked both the guage and the senders. OK

I pulled the thermostat and I am not sure what I am looking at or how they work. They are similar to part # 3675303/4142522

These are 2 1/4 x 3 - mine are 2 1/2 x 3 1/2 (approx.)

In the marineengineparts there are no thermostat for the years 69-74

Any help in finding a thermostat will be appreciated
 
"I have found with my 318, hal

"I have found with my 318, half closed cooling system, that the standard automotive 160 degree thermostat with a 3/16 hole drilled in the flange works just fine and very inexpensive.

Of course it is not advisable to use an automotive thermostat in a raw water cooled motor,if you are in salt water, you will need the marine brass type."
 
You can test the thermostats b

You can test the thermostats by putting them in a pot of hot water and raise the temperature while measuring the water temp with a thermometer. Be sure it closes back up when you cool it down. You should see it open at the rated temperature. Sometimes the temp is stamped into the housing.
 
Had the same problem with my 1

Had the same problem with my 1981 lm318---contact Hurrikain marine--they have a web site--great help and knew what I was looking for--I am just ordering a couple of more for the Spring
 
"We have the thermostats for t

"We have the thermostats for the 69-74 boats.. One thing to look at IS to make sure the thermostats are in correctly .. If I recall they can be put in upside down..You want the Top Hat UP.. Most folks think they would go in down in the manifold. ).. If you look up into the top of the t- stat housing you will see a seal up in the top. The Top hat needs to sit up against that. We have seen the seals go bad also, but it isn't a real common problem but worth looking at while it is apart. There is a 145 and a 160 degree available you will see it here: http://www.hurrikain.com/Chrysler-Thermostats.htm
Dave"
 
"One other thing you can check

"One other thing you can check....Is the T-stat seating tightly in the housing, or is the seat so rusted that water slips on past? Have this problem with mine so I epoxied a new T-stat to a stainless plate that looks just like a gasket. The water can no longer slip past now, and the motors warm right up.

Jeff

PS: Got a photo of this if you're interested."
 
"My problem is the opposite of

"My problem is the opposite of Stuart's. My 1975 Trojan rebuilt 318 overheats (bought in spring '08.). No T-stat was installed so I installed one. Still OH's. (Also, I'm new to boating so I'd like to learn about the cooling system possibly with water flow diagrams.) HELP! Thanks."
 
"Sean,
An easy way to help di

"Sean,
An easy way to help diagnose overheating is to temporarily remove the thermostat. This should cause the engine to run very cool assuming no ther problems. Do you have sea water cooled or fresh water cooled engine? If seawater, then you can check to be sure that plenty of sea water is able to get through the hull fitting and stop cock. On many installs, the seawater pump will pull water from the hull through a transmission cooler and up to the engine. On a 318, this pump is off to the side of the engine attached with a fan belt. It may need to be rebuilt. If you are able to, you can remove the hose from the outlet side of the pump and turn the engine over for a few seconds to see if it is pulling sea water from below the hull. If that checks out, then hook the hose back up and look at the engine recirculating pump that looks like it is actually part of the engine where the pulleys join together. These pumps are an arm and a leg, but they can be rebuilt in most cases. It is more likely that the hose coming into the boat is plugged and not allowing enough water to the pumps/engine. Are you blowing steam out the exhausts? If so, the problem is likely in the exhaust manifolds. If this is the case, get them checked or replace right away, since there is the possibility of blowing water into the cylinders (been there done that). It could also be something as simple as a bad temp sender or gauge. Hope this helps..."
 
Had overheating problem with m

Had overheating problem with mine as well this year. Problem turned out to be an air leak at the strainers. ANY air leak before the raw water pump will cause an amazing amount of trouble.

Jeff
 
Check your rubber impellers in

Check your rubber impellers in the raw water pumps. They are cheap ($24) and wear out or can crack. You have to flex each vane to see if its cracked.
 
"Thanks all for the advice. O

"Thanks all for the advice. Originally, there was no T-stat & I had OH's. Mechanic said to install the T=stat. I did, but it still OH's; i.e., the temp climbs as I hit high RPM, then I back off on the throttle & temp starts to decrease. I did have one occassion where I didn't watch the temp guage climb, we stopped at a favorite swimming spot for apprx 20 minutes. When we went to leave, she wouldn't start & the temp guage was almost pinged right. I let it cool down & checked the antifreeze level & it was low, so I added more antifrz & water. She started with no problem. while heading home, the temp guage would climb when I increased the RPM power. A boater friend checked the impeller & said it was good.
I think my cooling sys uses sea water to cool the fresh water via heat exchangers. Naturally, I'll try all of the good advice provided. Thanks again. (Is there some way of getting a cooling systme diagram for the 318?)

Sean"
 
"You need to clean out your ex

"You need to clean out your exchangers.

Attached is a cooling diagram for Chrysler 318/ 360 FWC engines.

Jeff
218683.jpg
FWC Cooling System
 
"Another possibility is a smal

"Another possibility is a small leak in the heat exchanger that causes loss of freshwater coolant when the engine heats and the pressure builds, forcing coolant into the seawater stream. This could be caused by winterizing problems leaving a crack in the exchanger internally... This would be a possible explanation for the coolant loss when the engine gets hot.. All the above assumes no steam in the exhaust."
 
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