2001 5.0 GLPEFS Overheating, running out of usual suspects.

Joined
Jul 23, 2016
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We recently bought a 2001 205 Sundowner with very low miles, original owner. During the test, everything was great. First time we took the boat out about a week later, it overheated as soon as we hit the harbor and would not cool back down. Forunately, we have Coast Guard friends and caught a tow back with them. So far we have checked the impeller, it looks great. All accessible hoses on the engine were checked and had no blockage. The thermostat was replaced, housing cleaned. The circ pump was also replaced. We ran the boat on muffs for a good 45 minutes, revved up and down, with absolutely no issues. We dropped the boat today and within 10 yards of the pier we had a high temp alarm. The hose going into the impeller is cold, and the line coming out going to the thermostat housing is hot. All of the hoses coming off the thermostat housing were scorching hot. What would the next step be? The boat ramp is about 45 minutes from our house, so we are trying to test as much as possible with muffs, but I am aware that limits some diagnostic abilities. Thank you for any help, we are really just hoping to get more than 5 minutes in the boat this summer!
 
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bajaunderground

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Apr 18, 2008
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1,401
Freshwater? Saltwater?

There's an overheating troubleshooting guide under the VP section under Adults Only. I would suggest isolating which sensor is reading high? You should have 3 two on the exhaust elbows and one on the front of the thermostat housing. Make sure your seawater pump is not sucking air (sounds as if your ruled that out as you say the pump is cool) I suggest double checking the thermostat housing by-pass (it feeds the water jacket of the fuel cell and allows water to flow into the engine. Sounds link blockage, back-flush and check risers?
 
Joined
Jul 23, 2016
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Thank you for the response! I found the troubleshooting guide and will go through that tomorrow. Forgive my ignorance, but what is the best way to isolate which switch it might be? Just remove them one by one? By isolating which one, it should help determine which section is actually overheating, correct? It makes sense in theory, I just have no experience and my husband is gone for a few weeks. I do have the repair manual, which I have been reading through to try to figure things out. I just can'tcan't figure out why it was great on muffs and instantly overheated in the harbor. Oh, it was salt water. Again, thanks for the help!
 

bajaunderground

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Joined
Apr 18, 2008
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1,401
Yes, just one at a time. There's some amperage or on/off ways as well, but to isolate the overheating, just pulling when alarm goes off will help. Don't get too hot for extended times...

So muffs are difficult to trouble shoot overheat issues as the water comes out of the hose with pressure and flow values... It can hide a bad impeller or an air leak or an occlusion. When the boat is in the water the sea pump is at or slightly below the water line which helps create the head pressure for drafting. Hope that makes some sense? There are others that know a lot more than I in regards to overheat issues... I just went thru it this spring!
 
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