www.iFourWinns.com :: View topic - overheating at idle

I have a 2008 h220 with mercruiser 5.0 and bravo 1 and recently had a bad sea water impeller that caused me to overheat. Since replacing impeller everything is much better but one formed hose was fatigued and needed replacement but still at idle for a while and temperature rises until alarm sounds. If I give it some rpm it cools right away. Im guessing its particles of old impeller which was totally disintegrated or could it be something else? Only 30 hours on boat so far.
New to this forum but great stuff out there so hoping someone can help.

jamesosullivan wrote:

ding ding ding ding ding

but after you take the thermostat out -- put it back (or a new one)

you also have to do more than just casually look inside -- the impeller parts can get past the thermostat and stuck in the smaller openings above the thermosts.

so actually remove the thermostat from the housing and look in all the small openings

Author:	jamesosullivan [ Thu Aug 25, 2011 9:10 pm ]
Post subject:	overheating at idle
I have a 2008 h220 with mercruiser 5.0 and bravo 1 and recently had a bad sea water impeller that caused me to overheat. Since replacing impeller everything is much better but one formed hose was fatigued and needed replacement but still at idle for a while and temperature rises until alarm sounds. If I give it some rpm it cools right away. Im guessing its particles of old impeller which was totally disintegrated or could it be something else? Only 30 hours on boat so far. New to this forum but great stuff out there so hoping someone can help.

Author:	ardy [ Fri Aug 26, 2011 2:40 am ]
Post subject:	Re: overheating at idle
Firstly welcome to the forum. Sorry I can't help with your dilema but I am confident that someone will chime in with the information that you need. Also couple of rules here 1) Post some pics 2) Post some more pics Hope this helps

Author:	ric [ Fri Aug 26, 2011 9:42 am ]
Post subject:	Re: overheating at idle
jamesosullivan wrote: I have a 2008 h220 with mercruiser 5.0 and bravo 1 and recently had a bad sea water impeller that caused me to overheat. Since replacing impeller everything is much better but one formed hose was fatigued and needed replacement but still at idle for a while and temperature rises until alarm sounds. If I give it some rpm it cools right away. Im guessing its particles of old impeller which was totally disintegrated or could it be something else? Only 30 hours on boat so far. New to this forum but great stuff out there so hoping someone can help. ding ding ding ding ding

Author:	Paul I. [ Fri Aug 26, 2011 12:38 pm ]
Post subject:	Re: overheating at idle
ric wrote: jamesosullivan wrote: I have a 2008 h220 with mercruiser 5.0 and bravo 1 and recently had a bad sea water impeller that caused me to overheat. Since replacing impeller everything is much better but one formed hose was fatigued and needed replacement but still at idle for a while and temperature rises until alarm sounds. If I give it some rpm it cools right away. Im guessing its particles of old impeller which was totally disintegrated or could it be something else? Only 30 hours on boat so far. New to this forum but great stuff out there so hoping someone can help. ding ding ding ding ding YOU ARE TOO FUNNY!!!!!!!

Author:	Paul I. [ Fri Aug 26, 2011 12:40 pm ]
Post subject:	Re: overheating at idle
jamesosullivan wrote: I have a 2008 h220 with mercruiser 5.0 and bravo 1 and recently had a bad sea water impeller that caused me to overheat. Since replacing impeller everything is much better but one formed hose was fatigued and needed replacement but still at idle for a while and temperature rises until alarm sounds. If I give it some rpm it cools right away. Im guessing its particles of old impeller which was totally disintegrated or could it be something else? Only 30 hours on boat so far. New to this forum but great stuff out there so hoping someone can help. Try taking the thermostat out. You might find something there, plus it is very easy to do.

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Author:	DaleG [ Fri Aug 26, 2011 12:48 pm ]
Post subject:	Re: overheating at idle
but after you take the thermostat out -- put it back (or a new one) you also have to do more than just casually look inside -- the impeller parts can get past the thermostat and stuck in the smaller openings above the thermosts. so actually remove the thermostat from the housing and look in all the small openings

Author:	LouC [ Fri Aug 26, 2011 12:55 pm ]
Post subject:	Re: overheating at idle
In addition to looking for pieces of the old impeller, when it was changed, did the mechanic also replace the wear plate and housing? If not these parts can sometimes wear and the pump won't pump that well at low rpms.....

Author:	Paul I. [ Sun Aug 28, 2011 11:05 am ]
Post subject:	Re: overheating at idle
DaleG wrote: but after you take the thermostat out -- put it back (or a new one) you also have to do more than just casually look inside -- the impeller parts can get past the thermostat and stuck in the smaller openings above the thermosts. so actually remove the thermostat from the housing and look in all the small openings Thank you!!! That is what I meant, take it out & put it back.

Author:	jamesosullivan [ Sun Aug 28, 2011 1:33 pm ]
Post subject:	Re: overheating at idle
thank you I'm going to give it a shot this weekend I replaced the thermostat already, so now I will take a closer look for small pieces of the impeller. Mechanic did not change housing or plate so that will be my next step if I don't see anything. I read somewhere there can be two balls and a spring inside some hose that could need tightening? How do I know if my set up has that? Where would they be located? I am looking forward to the responses and I will post what I find out as I dig in

Author:	ric [ Sun Aug 28, 2011 10:37 pm ]
Post subject:	Re: overheating at idle
my boat used to overheat when the impeller was bad, it was stiff and didn't let much water pass at low speed

Author:	TX H210SS [ Thu Sep 01, 2011 10:39 pm ]
Post subject:	Re: overheating at idle
I agree with what you have heard already - remove the therm and check all the ports in the therm yoke....from there remove each of the water supply lines one by one (isn't hard) and make sure all are clear of debris - then i would dump the water out of the engine block and exhaust manifolds......not a hard task and you may want to have a small probe to pull out any debris as the water drains from each of the ports (mani's and block). By doing this you may be able to flush out some of the debris. you also can buy a 30 dolla infared thermometer....run it on the muffs and start checking the lines, block and mani's in order to find out where the drastic temp change occurs. This will be your point of blockage. There may be a way to backflush the system, but research this extensively first - don't wind up dumping water into where water doesn't need to be.

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