2 ?'s... overheating and low power.

[1980Galaxy]

I have a 1985 mercruiser 120. i got 2 questions:

1. My engine keeps overheating. i suspected the water impeller so i took it apart and found that it looked brand new! i backflushed the hoses and everything looked good. i took apart the t-stat housing only to find out i didn't have a t-stat in there. so if anything, the engine should be running cold. I am thinking it would be the water pump on the engine. ideas? what else could it be?

2. The engine idles great in the driveway. Once i take it out on the lake and put it under a load, it runs like a dog. full throttle can't even put the front end in the air, much less try to get on plane. taking it back down to idle and shifting gears tends to stall it alot of the time. it has about 1/3 of the power it should have.

Over the winter I had a cracked block and had the mechanic put this new motor in. had new spark plugs put in, timing and all that tune up stuff done by the mechanic. So i take off the fuel/water seperator it was filled up about 2/3 of the way with water. so i got a new filter on there now. my question is: could that fuel filter be causing such a great loss of power? maybe a dumb question, im sorry. i just want to know if i should keep poking around for other potential problems or if that was most likely the cause.

thanks for reading all this, i really appreciate your help. I'm learning more and more about boats everyday and you guys are the main cause. Thanks again.

 

[stevp]

Re: 2 ?'s... overheating and low power.

what kind of engine ? whats the outdrive?

 

[1980Galaxy]

Re: 2 ?'s... overheating and low power.

as i said, 1985 mercruiser 120...

if the outdrive matters, its a 1 drive

 

[cr2k]

Re: 2 ?'s... overheating and low power.

Not having a T-stat does not mean it will run cold. It can run hot due to water flowing too fast to absorb heat. Also T-stat is kind of a water flow traffic cop in some housings and may just dump most of the water to the manifolds.

"looks new" doesn't always mean is functional as new on an impeller. I have replace several that looked good but it solved the problem. The only for sure about an impeller is if it looks bad it is.

 

[1980Galaxy]

Re: 2 ?'s... overheating and low power.

i changed the impeller anyway just because i had already bought a new one but that old one really looked prestine....

i also forgot to mention that the exhaust doesn't come out of the center of the prop, it comes out of the two holes on the side of the outdrive right by the transom. There was a similar thread about that on here and the problem was not enough water getting thru the system.

i'm gonna find a t-stat this week and see what that does for me.

anything about the 'low power'?

 

[dubs283]

Re: 2 ?'s... overheating and low power.

if there was water in the water separator, there is more in the fuel tank

need to drain the fuel tank and clean it out

start over with new fresh fuel and check the tune-up specs again

 

[1980Galaxy]

Re: 2 ?'s... overheating and low power.

sorry, also forgot to mention that it only overheats when under a load. if i drop back to idle, it cools itself back down.