Mercruiser 228 heating up?

4timesthefun

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Jun 18, 2012
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3
Engine has new t-stat and lower and upper water pump assy in outdrive. I have not had the boat in the water yet. Just on the hose. Just tuned and set timeing...engine idles well and no water in oil. Issue: On the hose, at idle and up to 1700 rpm's, engine will heat up, like t-stat isn't opening. If I take the t-stat out, engine runs cool to the touch, but will not warm up? Any ideas?
 

Bondo

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Apr 17, 2002
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70,465
Re: Mercruiser 228 heating up?

Engine has new t-stat and lower and upper water pump assy in outdrive. I have not had the boat in the water yet. Just on the hose. Just tuned and set timeing...engine idles well and no water in oil. Issue: On the hose, at idle and up to 1700 rpm's, engine will heat up, like t-stat isn't opening. If I take the t-stat out, engine runs cool to the touch, but will not warm up? Any ideas?

Ayuh,... Welcome Aboard,.... Water that get's In, is gotta be able to get Out,...

Find yer blockage....
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Mercruiser 228 heating up?

Like Bond-o said.... Check your exhaust elbows and manifolds.... (and check the thermostat in a pan of hot water and a thermometer)....
 

4timesthefun

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Jun 18, 2012
Messages
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Re: Mercruiser 228 heating up?

I did the t-stat test (160 degree stat). Honestly, it seemed to start opening hot, so i went to the auto part store and picked up a balanced (160 degree stat) and the engine did the same thing, started to heat up after about 5 minutes. So, i cut the guts out of the old t-stat and ran the engine for a good 30 minutes with the temp gauge in the green. Are you suggesting there is a blockage, not allowing the water out? If that were the case, wouldn't it also heat up without the t-stat because that's not the case? I know the manifolds/ risers are not cracked and are not leaking, but i have not checked them for blockages and will do so. I appreciate your input guys:)
 

patflemming

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Jul 7, 2014
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1
Did you solve this problem and if so how did you do? It seems I got the same issue with my 305 mercruiser 230. The motor runs hot but only with the t-stat. I have checked and dubble checked the t-stat and replaced with a brand new mercruiser 140f t-stat. Still the problem remains. If I remove the t-stat the motor is cold to the touch. Could it be flow check ball springs? Could it be the impeller not shovling enough water? Manifolds or risers?
 
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