T Stats
 

Today we fished in Long Island Sound everything was fine, on the way back in I came in from fishing @ 4400 rpm for about 20 minutes dropped down to 3000 rpm and the over heat alarm came on for 30 seconds as soon as I gave her some gas it shut off and never came on again. The guy in Outboard Exchange said it sounded like a T Stat hung up and said to change them. He sold me 2 and gaskets for 27. Is it as easy to change as he said it's like a car T Stat and does that sound like the problem? 1982 Merc 150

we dont have working thermostats we stuck them open and never will have to worry bout them again...

T Stats
 

I just removes them from the engine and they looked old and had white corrosion on them , dropped them in a pan on the stove and watched them open with a thermometer, they didn't open evenly, one was noticeably slower than the other, they started to open at 120 F and was fully open at 130 F. Closing one was smooth and the other just before shutting it snapped closed you could hear it. I 'll install them in the morning, what kind of sealer, Permatex #2 or silicone?
Water telltale is peeing out about 3 feet behind the engine, I don't think it's a water pump issue.

Working T-stats are a GOOD thing to have, those that block them open or bypass them will pay for it sooner or later and wish they would have put them back in. The factory doesn't spend money to put them in for nothing. Yes, T-stats in a V-6 MERC like yours are pretty easy and straight forward, just be careful not to break off the bolts as years of salt has a habit of welding them in.

Most motors run like crap at idle speed or trolling if the Tstats have been removed.
If you haven't done the water pump in a while, also plan to do it while you got the motor down for repairs.
I didn't remember using sealer when I replaced mine. Permatex has always been my favorite.

Oh, don't forget the Anti Seize!

ours runs great at idle and trolling speed so no probs there. And as far as paying for it eventually rob had an old 115 with bypassed stats and ran it for thousands of hours and had no problems.. so idk i just bypassed mine.

On some of the newer and older ones with elec fuel injection and sensors the eng temp determined how much fuel was injected into the cyl's, without the t stats the computer may overload or not give the eng enough fuel into the cyl's and either burn the cyl's up and seize the motor or flood the rings and wash the cyl walls and you'll eventually loose compression sooner than expected by the manufacture's history for the motor. You may not get max hp out of the motor.

Just my 2 cents worth

yeah i got some good old fashion carbs..:nice:

One of the biggest killers of 2 stroke outboards is carbon build-up, and running them cold is the biggest contributor to carbon build up there is. Some engines will live, but many will die a slow painful death until they eventually stick a piston form sticking rings or score a cylinder wall. I can't tell you how many times somebody has brought an engine to me complaining of how it idles or pours out black soot from the exhaust and come to find out it was the owners removing the t-stat that caused it. And what many don't think about is the T-stat is a restricto that is needed to reduce coolant flow and to allow the water to absorb engine heat rather than just pass through without absorbing heat. I've seen more engines overheat from no t-stat than I have overheat because of a bad one. And many people never think about a T-stat when doing there maintence, but it is a maintence item that needs to be replaced periodically depending upon useage.

My thermostats are still in there they are just open forever.

T Stats
 

I just replaced mine. After it warmed up it idles better than ever. After 15 minutes or so on the muffs you can still stick your hand on top of the head for about 30 seconds or so. Monday I'll take it for a ride to be sure but I'm confident that was the problem..........

I know some of teh go fast guys use nickles(or maybee its quarters), drilled out in the middle to offer some restriction in plae of thermostats.

But getting back to the original post, I don't think your engine had any type of rpm restriction in case of over heat, sorry to be the buzz kill, but if it reduced rpm's, it may be something else, you might want to do a compresion test

What happened I was going in to the buoys for the channel to get under the bridge I slowed down from 4400rpm or so to about 3000rpm for about 5 minutes of so when it happened ,I when to neutral then back in gear and it shut off and never came back on.........

You made me nervous about the motor that maybe a piston was melting down, so I did a compression test and everything was 118-120 psi same as before.........

your poppet valve opens around 2500 rpms or so. it lets more water in the powerhead above that speed. if you run your motor just below the speed that it opens your motor will run hot. if you have a water pressure guage you can watch as you slowly accelerate the pressure increases than drops(poppet opens) than increases again. long story short... you may need to replace the water pump. Merc pressure style water pumps like yours should be changed every other year. they are cheap enough and very easy to replace.

A water pressure guage goes a long way to keep your eye on the condition of your motor's cooling system. one of the best investments I ever added to mine!!

:nice:

T Stats
 

Just got back from a 1 hour run around the lake. NO MORE ALARM...Thanks for the help......

Can anyone tell me if an 84 90hp inline would have t-stats and if they do where would they be located?

Turbo