Thermostat - odd problem resolution.

[sschefer]

Last night when I got home I got a call from a guy with a 200 that was overheating. The shop he was taking it to couldn't resolve it and had changed everything. He asked if I had time to take a look at it.

He brought it by and we put it on the hose. The head temps climbed up to 160 on both sides (infrafred thermometer) and the tell tale was weak and spitting. Good water flow out the hub so the pump was working.

For lack of any other suspicions I pulled the thermostats and after looking at them for a few minutes I realized that the rubber grommet gaskets were upside down with the lip side pointed into the head instead of into the fitting. I flipped them both over and reinstalled them and WA LA.. temp head stabilized at 140 and the tell tale was strong.

For the life of me I couldn't see what was being blocked. Obviously something is. If you happen to have this problem this might be worth checking.

 

[mxzeatr]

Re: Thermostat - odd problem resolution.

Do you happen to have a pic of one that is correct? We put new stats in my motor with new gaskets, and there didn't appear to be a 'right or wrong' way...Wondering if its something I should check.

 

[sschefer]

Re: Thermostat - odd problem resolution.

Do you happen to have a pic of one that is correct? We put new stats in my motor with new gaskets, and there didn't appear to be a 'right or wrong' way...Wondering if its something I should check.

The grommets are flat on one side and have a lip on the other. When they're packaged the grommet is slid on the main body of the stat with the lip facing the top of the stat. There is a slit on the inside of the grommet. The grommet is slipped over the top of the stat's lip so that the stat lip is in that slit. The lip on the grommet needs to be facing outward into the fitting side and not into the head side.

I tore an engine down last night and still have the therms. I'll take a pic tonight.

 

[mxzeatr]

Re: Thermostat - odd problem resolution.

Ok.

I think I did mine right, but was just curious. If the boat wasn't 100 miles away I'd take one out quick tonight and look. Thanks!

 

[ufm82]

Re: Thermostat - odd problem resolution.

Very interesting- I've been having very odd overheat issues as of late and haven't found the problem- now I'm interested to see my t-stats. As Artie Johnson used to say, veeeeeeeeeeeeery interesting.

 

[Faztbullet]

Re: Thermostat - odd problem resolution.

Should not make any difference as t-stat it trapped between housing cover and water jacket and gromment makes the seal, in fact mine are reversed on the washers on my 200hp(holds em in place) and my 2.5 has no stats or poppit!!!!

 

[bullet88]

Re: Thermostat - odd problem resolution.

i just had my mercury promax rebuilt, within two minutes it overheated. they swear it has a new impeller. What do i need to check

 

[sschefer]

Re: Thermostat - odd problem resolution.

i just had my mercury promax rebuilt, within two minutes it overheated. they swear it has a new impeller. What do i need to check

I'm being serious here.. Check your warranty.. If you can, take it back or let them tell you what to look for. If you do anything to it other than what the rebuilder suggests you'll give them an easy out.

You have to be sooooooo careful with these types of things and it will drive you nuts but it's whats got to be done.

 

[sschefer]

Re: Thermostat - odd problem resolution.

Should not make any difference as t-stat it trapped between housing cover and water jacket and gromment makes the seal, in fact mine are reversed on the washers on my 200hp(holds em in place) and my 2.5 has no stats or poppit!!!!

It only seems to make a diff if you're running the stats and I can't figure out why. I'm guessing ...... it might be that they cover the bleed hole and create an air gap or something on that order. I really don't know for sure but it does make a difference.

Ahhh yes, but another Merc Mystery...LOL

 

[nbnewbie]

Re: Thermostat - odd problem resolution.

Should not make any difference as t-stat it trapped between housing cover and water jacket and gromment makes the seal, in fact mine are reversed on the washers on my 200hp(holds em in place) and my 2.5 has no stats or poppit!!!!

I'm curious as to why you're running no stats or poppit. Will you elaborate some please? TIA

 

[Faztbullet]

Re: Thermostat - odd problem resolution.

This is a factory "hot rod" engine and designed for WOT throttle running/(max cooling) and racing, aint worth a der on a stock bass boat or runabout....

 

[sschefer]

Re: Thermostat - odd problem resolution.

I'm curious as to why you're running no stats or poppit. Will you elaborate some please? TIA

All sorts of tricks are used on "Go Real Fast" motors. Nothing you want to try on a stock motor. Most "Go Real Fast" motors only last about 100 hours if the owners even wait that long before refreshing them. The one in FB's pictures comes from the factory with either no warranty or a 1 year I can't remember for sure. It also cost's about double what a normal motor does.