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View Full Version : What Happened to my Cooling System?


yippikaiyay
04-27-2008, 07:09 PM
First run of the season, and I had a problem with overheating.
I had brought the boat out of storage, gone through my de-winterization including a new impeller etc.etc. Fired the boat up in the driveway with my garden hose attachment, and all was running perfect. No leaks, lots of water discharging through exhaust flaps, all appeared normal.
After dropping the boat into the lake today, after about 10 minutes of running time, the water gauge started to creep up, and I was getting some considerable steam out of the exhaust - while on plane.
So I shut down, checked the intake screen, disassembled a number of the raw water hoses, and the impeller cover, and everything seemed to contain water.
The exhaust manifolds were definitely overheated.
So waited 45 minutes or so, fired back up, and just when I was getting ready to shut down, again, as I watched the water temp start to go past normal, it suddenly dropped, back to normal.
I ran it for about another 15 minutes, and all is good.
Any ideas on what happened??

Chief
04-27-2008, 07:49 PM
Lost it's prime? Good to hear everything went okay. Notice any extra water in the bildge? Maybe a leak somewhere?

Maybe theromstat stuck closed?

yippikaiyay
04-27-2008, 08:55 PM
Thanks for the advice, Chief.
No leaks, I'll re-tighten everything though, to be safe....and thermostat wise, can that fry an engine??
Is there any way to check their operation, or is just regular replacement that way to go?

Chief
04-27-2008, 09:40 PM
Thanks for the advice, Chief.
No leaks, I'll re-tighten everything though, to be safe....and thermostat wise, can that fry an engine??
Is there any way to check their operation, or is just regular replacement that way to go?

If it's sticking it will not open to allow water from raw water pump to go through block. While the block is heating up the thermostat is closed until it reaches 160 degrees then it will open allow water from the raw water pump to circulate through engine before that it's just cooling the exhaust risers. It will open and close to keep engine at operating temp. To test it remove it and put it in a pot of water and heat until you see it open. If there is rust in the block it can cause it to stick.

Replacing is a cheap option. Hope this helps.

teddy
04-27-2008, 09:43 PM
you can put the thermostat in water and boil it. If you have a cooking thermometer you can see when it open and closes. It may be just as easy to replace.

JimN
04-27-2008, 10:32 PM
OTOH, if the water is boiling and it doesn't open, you know it's bad and don't need a thermometer.

Have you ever lost the rubber vanes from an impeller and not found them? They can get stuck in the passages and make i t hard for the water to go where it needs to.

Do you open the petcocks or remove them when you drain the block? Never just rely on opening them. I would actually recommend removing them, toss them and replace them with plugs that come out completely.

stuartmcnair
04-27-2008, 11:02 PM
thermostat...had the exact same problem...new thermostat, no problem

TMCNo1
04-28-2008, 08:44 AM
Putting in a new thremostat is better than beating you head on the wall, and it's one less thing to address if it happens again anytime soon.

mayo93prostar
04-28-2008, 08:49 AM
it appears the thermostat was stuck and then it moved. i recommend replacing it. cheap part, bad results if stuck. have a good season. mine stuck a couple years ago and had to shut it down and get towed back to dock. this is why it is good to watch the gauges.

yippikaiyay
04-28-2008, 09:36 AM
OTOH, if the water is boiling and it doesn't open, you know it's bad and don't need a thermometer.

Have you ever lost the rubber vanes from an impeller and not found them? They can get stuck in the passages and make i t hard for the water to go where it needs to.

Do you open the petcocks or remove them when you drain the block? Never just rely on opening them. I would actually recommend removing them, toss them and replace them with plugs that come out completely.

Firstly, thanks to everyone for the input, much appreciated!
I have replaced my impeller every year, and no vanes have ever been missing. And, I've always removed the entire plugs to drain in the fall. I'll replace the thermostat and go from there.....

Prostar Rich
04-28-2008, 10:39 AM
Make sure that you get the right thermostat that the owners manual calls for.

Prostar Rich

rob935
04-28-2008, 03:59 PM
sounds like some kind of blockage , either the t-stat not opening or some kind of build up in the manifolds . quick way to check for deposits would be to remove one of your risers and have a look at the slots where the water passes through the manifold , any kind of blockage or build up here will have a huge affect on how your cooling works or doesnt as the case may be !!!

Romanod
04-29-2008, 09:50 PM
I had the same problem Sunday but, I had a leak from the drain plug on the exhaust. The plastic fitting split and the more I tightened the worse it got. I check the thermostat and it worked perfectly.


Found my problem! The Raw Water pump hose was reversed. When I drained it in the fall must have switched hoses. Easy to test. Remove hose after the raw water pump going to the block if it is sucking you got it reversed.