Where is my thermostat

[1dumbazz]

Hello every one I have a question
i have a mercruiser 170 4cyl
with a closed system I can’t find the thermostat
can anybody tell me where it is

p.s the reason I am trying to locate it is because I am having a overheating issue I just changed the impeller
flushed the system and it still overheats at higher speeds I can cruise all day without issues runs about
165 degrees but when I get it to speed it starts to overheat any ideas?

 

[Bt Doctur]

it`s inside the thermostat housing

 

[1dumbazz]

Haha I didn’t think of that!!!!!
i looked everywhere I can’t find the thermostat housing

 

[HT32BSX115]

Haha I didn’t think of that!!!!!
i looked everywhere I can’t find the thermostat housing

Maybe it's in the glove box of your truck.....Did you remove it and just misplace it?

I'm always putting my glasses down and can't find them. Just retrace your steps. You'll find it!! :thumb:

 

[achris]

Overheating at high speed is almost always a blocked/partial blocked exhaust elbow. Before you go ripping into the thermostat housing, check the elbow.

Chris......

 

[Scott Danforth]

did you find all the old impeller pieces?

when was the last time you had the end caps off the heat exchanger to clean out the tubes?

 

[Bt Doctur]

Just couldnt resist that comment
click to enlarge

 

[1dumbazz]

I had a local boat mechanic replace the impeller
when I changed the bellows and throttle cable
the old impeller was not broken just bent and dry

 

[HT32BSX115]

I can cruise all day without issues runs about
165 degrees but when I get it to speed it starts to overheat any ideas?

Overheats in closed cooled engines where it's OK until a certain higher power level are almost always clogging in the raw water circuit either from the raw water pump to the heat exchanger or exhaust manifold/riser cooling water output.

If you have an oil or power steering cooler, it's possible that you have debris or impeller fragments (or both) stuck in them or in the heat exchanger itself!.

Simple back-flushing can sometimes dislodge the "stuff" in there but sometimes it won't be enough.

My oil cooler is in the circuit directly after and down stream of the raw water pump and power steering cooler, but before the heat exchanger.

The oil cooler was so tightly clogged that I had to use needle-nose pliers to extract the impeller fragments. It was restricting flow to the heat exchanger that wasn't a problem until near cruise power settings.

If your heat exchanger is clogged, it might not be easy or even possible to completely clear it. You may have to take it to a radiator "guy" and have him (or her) take it apart to clean it out and re-solder it back together. Sometimes it may be easier and cheaper to just replace it.

 

[1dumbazz]

I will check the elbow and caps today
thank you for the advice and thank you
bt for the pic I will check that after the elbow and cap