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mercruiser 1976 cooling temps

Depends on what engine you got, some run cooler some run hotter. My volvo runs at lil less then the 200 mark. May need to replace the thermostat could be stuck closed. :)
 
Both of you checked the t-stat, got good water coming out of the transom hose going to the t-stat and or heat exchangers ?

Take it off run the boat with water going to the drive and hold the hose straight up got 12 inchs of water ? If yes then :

The heat exchanger is clogged or the riser is clogged.

That is if the hose is not kinked coming out of the transom.

That goes for both of you see you should be running no higher then 180 anything over and just under 200 is dangerously close to overheating this ain't a car motor.

Say your heat exchangers are clear and the riser ain't clogged then maybe you got a flapper / shutter fall down and is clogging your exhaust ?
 
Funny cause my 4cyl volvo penta engine runs a 198 thermostat in it, according to the service manual. Starts opening at 180 fully open at 198, or there abouts. Though she typically runs between those 2 temps. Heck the boat wont even move unless its at 140-160 or it will stall quick take off anyway.

Reason i was asking him was i have a copy of the big merc manual like 800 pages, and was checking to see what temp his thermostat is supposed to be. Though it doesnt say in it.

Raw water cooled engines do run around 140-150 or so at least the ones i worked on do, but only other boat engine i worked on is the popular gm 350.
 
Chiefalenl

Do you mean if I have water pressure that shots over 12 inches in the air I have a problem? I have not changed out the t stat since I have had the boat for 3 years. Can I hook up ear muffs to do the hose check leading to the t stat. When I pull that hose off the water should shots at least 12 inches in the air. Is that what you are saying?
thanks Dan
 
what he is saying is to remove the hose off the i believe before the raw water pump if the stream goes at-least a foot in the air then the hose and piping are not clogged and your looking at a clogged exhaust manifold/ t stat, heat exchanger etc.

My guess if the exchanger is fine then prolly the PO put an auto temp thermostat which would be hotter then the marine recommended one.
 
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