T-stat question

[BobList]

88 Force 125.. the coolant flow thru this engine is designed in such a way that even if the t-stat is stuck shut, you can look at the pee-holes shooting a good flow and be lulled into thinking everything is ok? My engine was running great yesterday, and I was giving it the how fast can it go routine, and died, fast. I think it locked up, blowing a headgasket in the process... it started back up ( sluggish cranking)a few minutes later, ran good, but with a lot of steam from the pee holes.. it seemed to have the slightest miss, though. It was hard to start a few times after that, cranking speed pretty good, and otherwise acted "normal". 'cept for a lot of steam from the holes.
I got it home pulled, the head, no obvious gasket damage. I also found out my O Heat buzzer must be inop. Cylinders and piston tops look ok. #2 cylinder, piston and head area dry, and clean, the rest were oily, normal looking. Water jacket area around cylinders seemed dry, considering it was in the water 45 minutes previous. I'm gonna do a new gasket, compression test, boil the t-stat to watch it open, or not, , and hope for the best.

So, basically, can you overheat due to a stuck t-stat, even though there is good flow from the holes?

Bob List

 

[pnwboat]

Re: T-stat question

When you say pee holes, are you referring to the two holes on the upper part of the lower unit where exhaust and water kind of spit out at idle speed? I don't trust myself enough to make that judgement so I installed a water pressure and water temperature gauge.

Back to your question if the motor can overheat if there appears to be good flow from the pee holes. That's kind of a matter of opinion. When you're at WOT, you normally don't see any or very little water coming out of those holes. This is when you have maximum water flow through the block. Only time you really see consistent water spitting out is at low or idle speed. Those are exhaust pressure relief holes to allow the motor to get rid of exhaust (mixed with cooling water) when the lower unit is deep in the water. At low or idle speed, the exhaust outlet just above the propeller is sitting much deeper and it takes more pressure to push the exhaust out. Once you get on plane, the lower unit is not so deep in the water and it takes less pressure to push the exhaust out so not much comes out of the two pee holes. I don't think you'll really get a good indication of water flow from looking at those two pee holes. A separate "Tell Tale" is much better. 1. It's not spurting out, you get a solid stream. Much easier to judge water flow. 2. You can get a good indication of water flow at all speeds.

Look under the FAQ section at the top of this Forum. It has a section that shows how to install a separate Tell Tale because it's a popular thing to do. I guess it's popular for a reason.

NOTE: Don't forget to check your water pump impeller too.

 

[BonairII]

Re: T-stat question

Installing a telltale will at least let you know that the impeller is pumping water. If it's located before the t-stat it won't let you know that water is cooling the block though(as is the case with my motor).

Having a functional overheat alarm is important. Get that taken care of.