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Coolant problem

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beebelawn

Well-known member
I finally got to put the boat in the water tonight and when it runs up around 3800-4000 it will start spitting water out the overflow. Right now I have a 16 lb. cap. I'm not sure if there is a problem or I just need to get a higher cap?? Any ideas?
 
Thats hotter than I run any of mine.
I would have a 165 degree thermostat and I would be shutting down if I hit 200 or trying to figure out why it is getting so hot.

Is your water pump belt tight? Is the radiator large? and getting plenty of air? Fins damaged?
 
You think the heat is why its puking antifreeze. Should I put the 165 thermostat in? The radiator was fine on a 454 with a 2 to 1 belt box that was on this boat before, but I did change out the gas tank and it may be blocking some. I had thought about putting an electric fan on there to help keep it cool.
 
I had the same problem but I was running a thermostat with the guts cut out ( kinda like just having a restricter plate) I just plugged up the overflow hole and now run a closed system. Haven't had a problem with it since, Just my 2 cents on this one.
 
You can try the thermostat. If that doesn't work, replace the cap (what lb.?) If it still pukes, I'd look toward head gaskets or a crack somewhere. There is a test kit at NAPA that picks up carbon monoxide in coolant when a leak is suspected. BTW, the kit isn't always accurate, depending on what type of leak, BUT if it shows positive, it is 100 % accurate. Sometimes it misses the other way if no carb mon reaches the coolant.
 
Don't run an electric fan that is a waste of money, think about it you have an 80'' fan that moves enough air to push a boat how much air does an electric fan push. Faron is right I like to keep my motors at 150 to 160. Some engine builders will say thats wrong and the motor needs to be 180. This doesn't work in an airboat. An airboat motor that runs at 150 when you beat on it running dry, can run miles before it hit's 200. However a motor that runs at 180 will over heat before you run the length of a football field. I would first run it with out a thermostat all together if it runs 150 to 160 your perfect if not then try using restrictors!
 
Something worth checking is your total ignition timing. Too much timing with crummy gas will over-heat an engine with the best of cooling systems.
 
Tried with no thermostat it would overheat real quick then. Timing is 9 at idle. 32 at most. 16 lb cap in it right now. The engine was just put together with all new parts. This was on the maiden voyage.
 
Put in a restrictor disk or just cut the gut's out of your thermostat! I would try around a 1'' size restrictor disk! Your timing is OK as long as your marks are correct!
 
Big Mac":3bvqjb15 said:
Something worth checking is your total ignition timing. Too much timing with crummy gas will over-heat an engine with the best of cooling systems.
Click to expand...



Big Mac,
Is dead on the money here! Check your timing and your plugs. If you ae going lean on the top side you will over heat under full load.


PS: I run an electric fan and I LOVE IT! If you bowfish or do a great deal of ideling around you can click on the fan. Also when you shut your boat off you can run the fan to cool your water off. Of course it does not add any cooling effect uder power as your prop pulls way more air.
 
I pretty sure there is no air in the line. Yes this a bowfishing boat. After running it around 4000 for a little while then you let it idle the temp starts climbing. I was wonder if the fan would help move air across the radiator when idling. The prop doesnt pull much air at idle at all. I'm idling at 500 rpms.
 
I also know a guy(name withheld) who plummed the system backwards..it would overheat and spit up after a few minutes.Don't overlook the simple solutions. Just this morning my 7.3 diesel was dripping fuel, did a little looking and found out a 10 cent gasket was the problem.....hope you get it solved.
 
Have you looked in the radiator for bubbles. It sounds like your cooling system is being presurized. Also check that rad in/out hoses aren't backwards, like Rich mentioned.
 
if you have a aluminum rad or heads make sure you use the red gm coolant and not the green it dont like aluminum
 
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