68 Nautique 390 ford overheating
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=39681
Printed Date: October-07-2024 at 6:20am
Topic: 68 Nautique 390 ford overheating
Posted By: 68nautique
Subject: 68 Nautique 390 ford overheating
Date Posted: August-15-2016 at 9:43pm
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Hi, I have a 1968 ski Nautique with the 390 ford interceptor engine and it has been overheating lately. It has a heat exchanger that cools the engine and the exhaust is cooled by the lake water from what I can tell. I checked the housing where the thermostat should be and I was surprised there wasn't a thermostat. I made sure there was no air in the system. When I run the engine I can see the flow of the coolant when I have the cap off the exchanger. It usually runs at 150 degrees under normal conditions but now just idling it gets to almost 190. Not sure what to do, any ideas? Thanks.
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Replies:
Posted By: SNobsessed
Date Posted: August-15-2016 at 10:42pm
Have you checked the raw water pump? The circulating pump may be doing good, but the RWP needs to bring in lake water at idle.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin
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Posted By: bwinn
Date Posted: August-15-2016 at 11:45pm
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Pics? Maybe push water backwards through the exchanger to see if it's plugged with debris? Just a guess
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Posted By: 8122pbrainard
Date Posted: August-16-2016 at 7:06am
Paul,
Pictures would be great. It does sound like your 390 is set up with a closed cooling system similar to a car or truck. On a marine engine, it's commonly called fresh water cooling except the closed portion of the system is cooled by water instead of air. Fresh water cooling on a marine engine is typically added when the engine will be run is salt/brackish water and or if there are aluminum components on the engine in contact with the cooling fluid.. The closed portion can be cleaned just like a car by using one of the radiator flushing products found at the auto supply. I suggest the flushing but first as Chris mentioned open up the RWP (raw water pump) and check the impeller. The RWP will be a pump added to the engine to bring in lake water. Follow the hose from the thru hull fitting on the bottom of the hull to first belt driven pump. BTW, there should be a T stat. Maybe a PO was a hack and removed it as a back yard crutch for the overheat problem?? Check all the hoses on the suction side of the RWP for general condition and tightness at all the connections since the RWP may also be sucking air.
How have you determined the engine is a 390? A 352 would be more common in a SN of that era..
Welcome to CCfan. Yes, picture would be great plus tell us more about the boat. Have you had it very long? There's also a 1st generation SN registry thread that you shound check out and contribute to. http://www.correctcraftfan.com/forum/forum_posts.asp?TID=39633&title=1st-generation-ski-nautique-roster" rel="nofollow - 1st generation SN roster thread Besides the roster, a diary entry is always welcomed.
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/diaries/details.asp?ID=1622" rel="nofollow -
54 Atom
/diaries/details.asp?ID=2179" rel="nofollow - 77 Tique
64 X55 Dunphy
Keep it original, Pete
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