5.0 L overheat questions, after trying all I can to diagnose.

[Ark-86]

Hello iboats members

I count this site among my most valued resources The wealth of info in the archives, stickys, etc is incredible. I have tried to avoid this post by searching the archives for info, but am unable to find a couple of answers I think can be quickly dealt with by an experienced VP person.

I have a 2001 20 ft Glastron with a 5.0 L GL / SX. (Motor is also a 2001). Bought last August, dealer maintained, pristine condition, used a few times, worked flawlessly. Winterized according to the manual, changed oils, impeller, and took it out for an hour run 2 weeks ago. had a couple of minor issues: A faint squeal I thought may be a belt. Belts are tight, noise seemed to fade away. Trim pump was a bit noisy, reservoir was low, topped it up to line.

Here's where the trouble starts: Went out Friday eve, warmed it up on the trailer, engine overheated and alarm came on as soon as we started to pull away. Shut down, cooled off, idled 100 ft back to the trailer with the alarm screaming, but kept the temp in the just above normal range. I had noticed a lot more mud / sand stirred up around the prop coming off the trailer than usual. I think the bottom has changed with the spring freshet in the river where I launch. (not a boat ramp). Checked for blockage at the intake screens, no muck there.

Tried it again on the trailer, still overheating. Pulled the impeller, looked fine, no sand as expected. tried a new one anyway. no difference. Sucked on the inlet hose from the raw water pump, pulled up water while on the trailer in the river. Pulled out of the water...ran water into the flush hose fitting with the engine turned off. and discovered water coming out around the plastic pipes where they go into the brass impeller housing. As I've read here, a new housing is needed. I'll order one today, but just to rule out other problems, I shoved a very tight 3" piece of heater or rad hose over each bad joint and clamped them off, 4 clamps. Water leak stopped completely.

Primed the raw water pump from the top of the hose on the thermostat housing, just to help it get rolling, then back in the river on the trailer. After what seemed like a long time idling, but may have only been 5 min, it overheated again.

Finally, my questions:

Would a bad thermostat cause an overheat?
Could the water circulating pump be shot?
Is the sucked up mud and the bad raw water pump fittings possibly just a coincidence?

What to do now? If take it to a dealer, i won't see it again this summer, and will spend a small fortune, I'm sure.

Thanks in advance for some advice guys!

 

[skydiveD30571]

Re: 5.0 L overheat questions, after trying all I can to diagnose.

A thermostat stuck closed could cause an overheat, yes.
Anything could go bad, but a circulating pump isn't high on the list of usual failures.

You can almost bet your overheating issue is related to sucking up mud. You said you're replacing the pump, and that should include the impeller too. Just because it looks good doesn't mean it is. Pull the thermostat housing and check the passages. They are small and can clog when debris is sucked up the intake.

 

[Ark-86]

Re: 5.0 L overheat questions, after trying all I can to diagnose.

A thermostat stuck closed could cause an overheat, yes.
Anything could go bad, but a circulating pump isn't high on the list of usual failures.

You can almost bet your overheating issue is related to sucking up mud. You said you're replacing the pump, and that should include the impeller too. Just because it looks good doesn't mean it is. Pull the thermostat housing and check the passages. They are small and can clog when debris is sucked up the intake.

Thanks Skydive. Replaced impeller, no fix there. Will check thermostat housing passages and test thermo while I have it apart. I saw a test of the impeller described, where you hold the top of the output hose level with the flame arrestor and see if it will pump water an inch high. could easily try that on the trailer in the water as well if no clogs and thermo working correctly.

Cheers from the east coast!

 

[mikeneal]

Re: 5.0 L overheat questions, after trying all I can to diagnose.

Somewhere ( I think it's a sticky) Don S has posted a great overheat troubleshoot flow chart.

 

[Ark-86]

Suck-Sess! Overheat Solved 5.0 L VP, iboats came through again.

Suck-Sess! Overheat Solved 5.0 L VP, iboats came through again.

After trying a new impeller, checking thermostat and housing for clogs, back-flushing, flow testing, priming, fixing leaky joints on raw water pump, and I can't remember what else, I read a thread from last summer about a similar problem. Seemingly good pump and new impeller, no air leaks after a couple of clamps etc, would not suck water at idle on muffs. He put it in the water and revved the motor to 2000 RPM.

I tried it after taking the boat off the trailer to give it less height to pull from. Primed the pump again for the heck of it, and away it went. Ran it 2 hrs off and on. (even towed home a couple of guys paddling the smallest speedboat I have ever seen.) Never got near overheating, either at idle or cruising.

Thanks to Skydiver for the reply, and all who take the time to post their issues, advice, and resolutions. I'll continue to buy parts etc from iboats and spread the good word.

 

[mikeneal]

Re: 5.0 L overheat questions, after trying all I can to diagnose.

I had an odd over heat with my 5.0GL a couple years ago and turned out the nylon fitting in the transom shield was racked and it would sometimes lose prime.