Thermostat Question

[CraigBarnard]

I have read through the manual and I cannot seem to locate the thermostat for my engine.
Its a 4 cyl. Mercruiser 120 hp not sure of the year but its in my 1965 Starcraft Cheiftain.
I did find one thermostat at the exhaust elbow but I have been told its only a "failsafe" t-stat. Not the main one.
I have attached a couple of pics of the engine. Could somebody locate the proper location for the t-stat.

thanks

 

[jimbo_jwc]

Re: Thermostat Question

Most i've seen are at the top block where your tempature sending unit and brass drain / vent plug are . Mine has 145 degree in it .Pic 1/of 4 looks like silicone high temp was used before.

 

[grzzzz]

Re: Thermostat Question

Just went through that 2 weeks ago. Had all those "places" apart. Only one I found is the one you found. That is the only one the parts books show. I have a 66 110 but they all look about the same. I was concerned because my gauge would go UP TO the red line and stop when idling. Dropped down at increased RPM. Changed gauge. Changed the thermostat,(145) took off every part that could be hiding one, new impeller, Still did it. Got a mechanical gauge and put it in so I could read real numbers. It went up to 160 at idle. So I determined that the beginning of the red line on the old color gauges was 160. Not over heating but at the line.

I don't believe you could put 2 thermostats in the same fluid flow and ever get any good temp control. I could be wrong.

Grzzzz

 

[Don S]

Re: Thermostat Question

I did find one thermostat at the exhaust elbow but I have been told its only a "failsafe" t-stat.

That is the only one. Did that "I have been told" person try to sell you any bridges?

When was the last time the raw water pump impeller was replaced?

 

[dozerII]

Re: Thermostat Question

Picture #4 is normaly where the t-stat is located, slightly different looking than my 72 120 though.
Glen

 

[CraigBarnard]

Re: Thermostat Question

Replaced the impeller just the other day.
How does that one at the elbow control the water in the block? It only has a small copper tube leading to it as far as i can tell.
It does not look to me like it would allow enough circulation to do much. Not familiar at all with how this works.

 

[CraigBarnard]

Re: Thermostat Question

Picture #4 is normaly where the t-stat is located, slightly different looking than my 72 120 though.
Glen

Thats what I would have thought too. Nothing under that housing. There is one located in pic #3
Weird.

 

[Pete104]

Re: Thermostat Question

My info was way wrong, so I took it out!

 

[dozerII]

Re: Thermostat Question

I tried looking up a tstat on a couple of sites and all the 120 are very similar. The only ones I could find that look like your photos are for the 110 which shows exactly the same parts as yours. Here is a link to the schematics, http://www.boats.net/parts/search/M...AUST ELBOW (ALUMINUM - 5-16"BOLTS)/parts.html From what I can see there is a relief valve and a tstat, the only tstat is located where yours is.I hope this helps.
Glen

 

[CraigBarnard]

Re: Thermostat Question

Well my first indication that it was a 120 hp was the label on the top of the valve cover that says "Mercruiser 120 hp".

As you can see in the following pics.



Also all the parts I have already installed on this engine are for the GM engine.
Which included spark plugs, distributer cap, rotor, ignition wires and a pointless ignition converstion.
As well as the thermostat.
All very easy to attain and install.
These are the facts that led me to believe its a a 120 hp.

 

[CraigBarnard]

Re: Thermostat Question

I tried looking up a tstat on a couple of sites and all the 120 are very similar. The only ones I could find that look like your photos are for the 110 which shows exactly the same parts as yours. Here is a link to the schematics, http://www.boats.net/parts/search/M...AUST ELBOW (ALUMINUM - 5-16"BOLTS)/parts.html From what I can see there is a relief valve and a tstat, the only tstat is located where yours is.I hope this helps.
Glen

Thanks! that pretty much tells me it is a GM motor.
Looks like I did find the proper location afterall but I did want to verify my conculsions.

 

[Don S]

Re: Thermostat Question

What you have is a Renault 60,80 or 90!

No, he has a 120 Mercruiser. Just a very old one.

There is only one thermostat. Until you understand the housing and what it does, you will not see how it cools the engine.
PS: Merc did change the cooling system in 72. Welcome to the wonderful world of Merc antiques.

 

[CraigBarnard]

Re: Thermostat Question

Thanks