1987 Mercruiser alpha V6 175 twins one is overheating

[Rodster44]

Hi
My friend is having trouble with one of his engines. It was overheating. They replaced the impeller and thermostat. After that it runs cool at idle but heats up above idle. It is run in fresh water only and has fresh water cooling. Can anybody give me any ideas as what to check next?

My friend said that is looked like smoke out the exhaust but a mechanic out there said it was steam.

He wanted me to ask if the buttefly could have anything to do with this ?

Thanks in advance
Rod

 

[Bt Doctur]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

fresh water cooled means a heat exchanger and A/F. clogged rises are likely.

 

[Don S]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

They replaced the impeller

Where was this impeller? In the drive or belt driven on the engine?
Since you have fresh water cooling (Heat exchanger) it may have both type pumps, if your mechanic changed only the drive pump and it's using the engine pump, then the wrong one was changed.

He wanted me to ask if the buttefly could have anything to do with this ?

Depends on what he is calling a butterfly.

 

[Rodster44]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

I may have used the wrong term. It does not have a heat exchanger. Not a closed system. It pumps lake water into the engine. They changed the impeller in the outdrive.
Thanks Rod
PS. they were asking about the butterfly in the exhaust.

 

[Don S]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

PS. they were asking about the butterfly in the exhaust.

Those are commonly known as either flappers or shutters, and no they shouldn't have anything to do with an overheat at anything under WOT. When you say it overheats above idle, is that any rpm above idle? Like 1500 rpm. Does it overheat under load only?
Is your overheat in the water or on muffs?

 

[Rodster44]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

I called him. He said at about 2500 RPM it heats up and It does not matter if it is in neutral or in gear. He is in the water and not running muffs.
Thanks Rod

 

[Don S]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

You just don't have enough water flow. Could be anything from the pump to the exhaust is plugged up. Or maybe at 2500 rpm the boat gets on plane and the pump is above the water level and sucking air. Was new gaskets installed? is the water hose going from the drive to the gimbal housing kinked? Is the thermostat installed correctly? All hoses routed correctly?

 

[Rodster44]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

I have not been out at the marina. I called my friend and they are going to pull the boat back out of the water and check hoses tomorrow. they worked on it all day today with no luck.
Thanks For the help
Rod

 

[Rodster44]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

My friend said they finally fixed it. I did not get all the details yet but something about a gasket in the outdrive close to the impeller. I will report back if I get better details.
Rod

 

[Rodster44]

Re: 1987 Mercruiser alpha V6 175 twins one is overheating

I never did get the details about what was wrong , Just that they messed up changing the impeller.
Rod