100 HP Outboard T-Stat Question

l_striker

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Can anyone tell me (or provide a diagram) where to find the t-stat on my 1988 Merc 100 HP outboard?
 

HD Fatboy?

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Re: 100 HP Outboard T-Stat Question

If it is like my 115 I don't think it has one.
 

l_striker

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Re: 100 HP Outboard T-Stat Question

Does your 115 spit water through the "tell tale" on a cold start, in netural, using muff's? I just changed my impeller, ruled out a hose blockeage, and nothing is coming out. I was thinking the t-stat could be stuck shut since the boat was always used in salt water.
 

Dave1027

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Re: 100 HP Outboard T-Stat Question

Can anyone tell me (or provide a diagram) where to find the t-stat on my 1988 Merc 100 HP outboard?

Looking at the back of the motor, it's at the upper left corner, next to the #1 spark plug. You'll see a cover about 4 or 5 inches long which houses two circular objects. The small object on top is the t-stat. The larger in the bottom part is the poppet valve.
 

Dave1027

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Re: 100 HP Outboard T-Stat Question

Does your 115 spit water through the "tell tale" on a cold start, in netural, using muff's? I just changed my impeller, ruled out a hose blockeage, and nothing is coming out. I was thinking the t-stat could be stuck shut since the boat was always used in salt water.
Before you go too far you should first consider the more simple and more likely causes. Remove the tell tail nozzle and blow compressed air backwards through it. Those nozzles clog all the time.
 

l_striker

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Re: 100 HP Outboard T-Stat Question

Thanks. I removed the hose and blew compressed air through it without an issue. I also blew it the opposite way just to be sure. The one thing I didn't do is replace the gasket on the water pump but it should spit out a little bit of water though even if it's no 100% sealed, right? By the way, I made sure the impeller was facing the right way and that the key was in place.
 

Dave1027

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Re: 100 HP Outboard T-Stat Question

Does your 115 spit water through the "tell tale" on a cold start, in netural, using muff's? I just changed my impeller, ruled out a hose blockeage, and nothing is coming out. I was thinking the t-stat could be stuck shut since the boat was always used in salt water.

Nope. The tell tail should be squirting water even with the t-stat closed. Mine begins squirting within 10 seconds of a cold start. This is in the water not on muffs, but I don't know if it makes a difference.
 

l_striker

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Re: 100 HP Outboard T-Stat Question

I wouldn't think so but stranger things have happened. One more question, is swapping out the t-stat pretty straight forward? The impeller was a breeze.
 

Dave1027

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Re: 100 HP Outboard T-Stat Question

Looks pretty easy but why do you still think the problem is the t-stat?
 

l_striker

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Re: 100 HP Outboard T-Stat Question

At this point I'm at a loss of what else to try next. I figure for $10, even if it's not the problem, it couldn't hurt to change it. I'm thinking about dropping in the water to see if it works but I'd hate to go through all of that effort if it doesn't. Any other suggestions would be greatly appreciated!
 
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