NEW Thermostat issue

[ron3033]

1995 Four Winn, 200 Horizon, 5.0 litre (Ford block I Believe) model 502APHUE OMC Cobra (this info on valve cover) This was about the time Volvo Penta and OMC merged.... I have a Volvo Penta SX Cobra Outdrive and says OMC Cobra on engine valve cover sticker.

I installed a new thermostat on Aug 10, Aug 14 went for a ride, gauge read a needle pointer above 150 f mark, so about 152 to 155 f at 3000 to 3200 rpm. Even with a 4200 rpm stayed about the same. About a hour down and a stop and an hour home all was exact same. Went out Aug 19, about 3000 to 3200 rpm about hour down the gauge was exact same as before. On way home it ran 139 to 142 f, same rpm..... at marina while I idle to get to launch dock it went to 150 f.

This is a new thermostat, o ring retainer, and gasket. Why would I get this sudden change in temperature? I can only think maybe a bit of debris got picked up at the marina I stopped at? I think there was 6 or 7 feet water at that dock.

Any Ideas why the temp would change. Maybe next run it will clear itself as it is on the trailer at home, and engine has completely cooled?

The boat is in showroom condition hopefully phots from marina I stopped at on Aug 19, 2018 are in my photos
https://www.iboats.com/ideabook/ron3033-photos

Thanks
ron3033

 

[ron3033]

new installed thermostat issues

I posted here as well as not sure this is all OMC, All Volvo Penta, or combination of the two???

1995 Four Winn, 200 Horizon, 5.0 litre (Ford block I Believe) model 502APHUE OMC Cobra (this info on valve cover) This was about the time Volvo Penta and OMC merged.... I have a Volvo Penta SX Cobra Outdrive and says OMC Cobra on engine valve cover sticker.

I installed a new thermostat on Aug 10, Aug 14 went for a ride, gauge read a needle pointer above 150 f mark, so about 152 to 155 f at 3000 to 3200 rpm. Even with a 4200 rpm stayed about the same. About a hour down and a stop and an hour home all was exact same. Went out Aug 19, about 3000 to 3200 rpm about hour down the gauge was exact same as before. On way home it ran 139 to 142 f, same rpm..... at marina while I idle to get to launch dock it went to 150 f.

This is a new thermostat, o ring retainer, and gasket. Why would I get this sudden change in temperature? I can only think maybe a bit of debris got picked up at the marina I stopped at? I think there was 6 or 7 feet water at that dock.

Any Ideas why the temp would change. Maybe next run it will clear itself as it is on the trailer at home, and engine has completely cooled?

The boat is in showroom condition hopefully phots from marina I stopped at on Aug 19, 2018 are in my photos
https://www.iboats.com/ideabook/ron3033-photos

Thanks
ron3033

 

[Lou C]

First the boat is immaculate, beautiful! I have an '88 that got a new deck in 2007, much of the interior has been replaced and it got a top end engine overhaul last summer (reman cyl heads, all new center riser exhaust and conversion to Holley 4bbl carb).
Dash gauges are not 100 % accurate but one problem I have had is similar, due to raw water cooling causing a lot of rust flakes inside the intake manifold, one little flake will hold the 'stat partly open and you will get lower than normal temps like 120* typically. I would not worry about it, a good run on plane may clear it out. What you can do is at the beginning of next season, remove the stat housing and clean out the intake area right below it, you will probably find some rust flakes there. Then take the stat and hang it by a bent coat hanger in a pot of water and heat it up, watch to see if it opens and closes all the way as the water cools. I usually do this at the start of each season. In a few years I am going to re-power this boat as the bottom end of the engine is original. Then I will start with a new GM marine engine and add closed cooling, this will end any sticky thermostat issues because the engine will have antifreeze in it as GM intended.....

 

[vasy]

It should be a bit hotter at idle as you get less water flow.
Water temperature itself can make a difference plus the condition of the water pump.
Also thermostat opens and closes, so it will heat up a bit, then cool down, not gonna be same temperature all the time.
10 degree is not really that big of a deal is it?
Also, how was it before the change? What temp thermostat did you get?

 

[ron3033]

HI Lou C Thanks for the reply. Yes the boat is like new... I wax it every year, and I live less than a mile from marina so it comes home each time It only got 2 uses summer of 2017...we had a very cold wet summer til 7 days end of Sept. and only 3 so far this year as I had surgery.

When I pull out the thermostat to immerse in water to clean as you instructed..... so this opens it full to clean?
1. I would need to get a new o ring that holds it in place?
2. A new housing gasket as well? I did not put any sealer on the gasket, but I scraped the old 22 yr old gasket off the 2 surfaces and polished with 275 sand paper to clean.

Another question
My outdrive creeps down on the trailer about 1 3/4 to 2 inches in 4 to 5 days. I bought the new style bidirectional seals for the lift pistons (they are supposed to be better than the old 3 piece seals. I have the old style pump (no reservoir) SEE Photos. How can I tell if it is the lift pistons or the valve body on the pump is the issue?? ... I am getting varied opinions. and the pump is in a very awkward spot to get at, and I had hand surgery and have to get the other hand done too.

One thing I read some place was to open and close the manual relief valve, that cured one person's problem...I am afraid it may worsen mine and the valve was so tight I could not turn it as you need to use a stubby straight blade to get at.

https://www.iboats.com/ideabook/ron3033-photos (shows lift pistons, pump, and new style rebuild seals)

Thanks Again Lou

 

[Lou C]

The rubber ring that holds it in you can re-use. I would get a few spare gaskets. I use a razor blade (carefully!!) to scrape the intake and the thermo housing clean and use Permatex Aviation sealer on the gasket and bolts. Never had a leak in all the years I've had it. Yes the heating in a pot will allow any rust flakes to fall out. When running on plane you'd think it would but it often does not. Must be how the water flows around it. The trim problem, well that is one thing I never had with my 30 year old Cobra. There is a guy on you tube who has a series of vids on a OMC Cobra boat and he has fixed the trim problem, see if you can find it, forget his name but his vids are good.

 

[ron3033]

Hi It was a 160 Fahrenheit same as came out. The original, 1995, ran 122 for years, then creeper up to140 to 150...It was kind of erratic. I figured 1995, time to change.
but on Tues same trip and rans 152 ish both ways.... Sunday trip, same trip, same rpm. 152 ish down, an hour later going home it ran 139 to 142 fahrenheit.
I can only think a bit of debris.... I don,t think the new thermostat failed in 3 hours use? Iwas stopped about an hour or less on Sunday at the other marina, then headed home.
Thanks
ron3033

 

[ron3033]

Hi
I am wonder thermostat failure but it is new, and your prior post about debris or rust keeping open makes sense. Just maddening all the time to do , and less than 4 hours use and it goes to different temp in an hour?
I did not know you could reuse the O ring....it took a while to get it in good and tight. As for the gasket,,, I guess if I have to take apart I will need a new one?? I put it on dry???
Does the Permatex Aviation sealer make take apart a real chore of scape and sand as it make the gasket pretty much permanent?

I am trying to determine pump, or lift pistons hate to fix pistons and find it is the pump or vice versa.
His name is Michael Romer

https://www.youtube.com/watch?v=xNnZePASXsM

 

[vasy]

if it failed, you would see the temp jump high, not a few degrees here or there.
Check the impeller condition just for fun. having a 160 thermostat and getting to 155 seems perfectly normal to me.
Normal operating range should be: 150-160 from my understanding how thermostats work.

 

[bruceb58]

Buy an IR thermometer and verify that your gauge and reality match. It may have always shown this variation and you never noticed it before. Mine moves around as well. I have a 140° in mine.

 

[Lou C]

I have checked them on and off for years and have found that the area on the intake manifold right under the thermo housing reads the closest to the dash gauge, usually about 10 degrees less.

 

[Lou C]

Yep that is his name...
The Permatex does not get hard. It seals well and also you put the sealer on the bolt threads and they will not rust in place, they will come right out. As I am in a salt water region, I use either this, or OMC gasket sealer on all the bolts on the drive, and many on the engine (even for exhaust systems) as it really does prevent bolts seizing up due to corrosion. You can replace the rubber ring if it got torn up removing it but I use a small screwdriver to carefully pry it out (or a pick) and am able to re-use them.
The trim rams I can't help with as that is about the only problem I have not experienced.....yet....lol....maybe because I have always stored the drive down....

 

[ron3033]

Hi Lou

when I put the thermostat in the housing and the o ring I did not use any sealer Like Permatex Aviation Sealer, Should I have done that?

 

[ron3033]

HI all when I put the thermostat in the housing and the o ring I did not use any sealer Like Permatex Aviation Sealer,

Should I have done that?

 

[Scott Danforth]

could be debris holding the t-stat open
could be bad gauge
could be bad sender
could be bad connection between them


as Bruce mentioned, get an IR thermometer and read what you really have at the block. best $15 you will spend.

 

[Lou C]

No sealer needed for the o ring only for the gasket between the thermo housing and intake manifold. Put some on the bolt threads too

 

[USA_boater]

I recently changed my t-stat, OEM in '04 was 150* stat. I used Indian Head Permatex gasket Shellac on the stat to housing sealing surface and then put in a new o-ring which probably also got some of the excess shellac on it which I figured would hold it in there better too.

I saw the permatex aviation sealer at the parts store but there were several kinds and I wasn't sure so I just went with the shellac since it is safer (no solvent fumes) and has worked for me for years on other applications. I also replaced the t-stat gasket and as Lou said, I bought several...a 2-pack of Sierra (with the gold brads) and a single OEM Volvo gasket. I went ahead and tried the sierra this time around and shellac'd it to the housing but DID NOT put any shellac on the intake manifold flange because I figured I did a good enough job of cleaning the sealing surface. However, upon a test run on the trailer, the gasket was sweating a tad bit until it warmed up..The Volvo gasket is more well made so I suspect it would have been fine to use without shellac. But the Volvo gasket has a smaller inside diameter and covered part of the intake manifold flange opening and I'm dealing with rust in the system so I wanted the best possible flow which is why I used the sierra gaskets which did not even cover the entire flange at all.

May I ask - how were you determining the temp for the numbers you gave? Did you use gauge only or IR? ALSO - what is the half-way point on your gauge? Mine is 120-220 so I "assume" the half-way is 170*?

 

[USA_boater]

No sealer needed for the o ring only for the gasket between the thermo housing and intake manifold. Put some on the bolt threads too

I used teflon tape on the water pump bolt threads and copper anti-seize on the t-stat housing bolt threads...is that okay Lou? Not hijacking, this is related to OP's issues so maybe some of my questions will help him out.

 

[Lou C]

It should be OK, I use the sealer because that's what OMC recommended in the '88 OMC factory shop manual I have. They recommend their sealer but the Permatex Aviation is nearly the same thing. Just a tad darker in color. It does not harden.
I have been doing it this way with out problems about 15 years worth....100% salt water use.

The one time you would NOT want to use any kind of copper anti seize is on threads that go into aluminum, because it will cause galvanic corrosion. Aluminum is less noble than copper. I like the gasket sealer because its basically inert. It will never cause galvanic corrosion but anti-seize in a wet environment can. And, the OEM in this case (OMC) recommended only sealers never anti seize in all their service literature. All these years I've replaced the thermostats (or at least pulled them out to clean out rust flakes) and I've never had any trouble with the thermostat housing bolts.

In an aluminum engine, or on your transom mount or outdrive DO NOT USE antiseize, even in fresh water it can and will cause galvanic corrosion if it contains any metal more noble than aluminum. Use only OMC gasket sealer, Merc Perfect seal or Permatex Aviation.....

 

[USA_boater]

Okay so the aviation stuff doesn't harden???...the gasket shelac does harden and is probably harder to remove. It says on the bottle it can be sued for threads and resists most fuels and water, etc. I guess I could use it in most places where you use the aviation sealer but it would make it harder to remove vs. aviation sealer?