mercruiser 888, aftermarket closed cooling system

[wolf21851]

I have a 74 24 foot chaparral with a 302. I put a aftermarket closed cooling system on it. it seems to cool the engine OK, but when I let off the throttle its temp seems to go way up and pushes the engine cooling water out the over flow. I have made a receiver tank for that, but is it supposed to do that. I am using the raw water pump in the lower unit. should I put a jabsco raw water pump on the engine, and if so would I be able to hook that to the lower unit or would I have to use a through hull with strainer. I am using a standard automotive thermostat housing. the cooling system came off of another 302 with omc stern drive. so is it supposed to do that or do I have everything wrong??? any input would be greatly appreciated???

 

[haulnazz15]

Re: mercruiser 888, aftermarket closed cooling system

You can't run a closed cooling system off of the outdrive pump. It doesn't support the flow needed for the heat exchanger, you'll need an engine driven pump.

 

[MarkSee]

Re: mercruiser 888, aftermarket closed cooling system

....I put a aftermarket closed cooling system on it. ...
.....any input would be greatly appreciated???

Are you saying you recently put this cooling system on?

Is/was the motor used in salt water?

Just trying to understand how it was used as putting on a fresh water cooling system on an engine block that has been used in salt water for more than a few months is generally not recommended and can cause further problems.

If at some point the engine was rebuilt and first completely sanitized then used only in fresh water you might be able to get away with it.

Mark

 

[wolf21851]

Re: mercruiser 888, aftermarket closed cooling system

You can't run a closed cooling system off of the outdrive pump. It doesn't support the flow needed for the heat exchanger, you'll need an engine driven pump.

Thank you for the info. one more question, will the engine driven pump pull thru the lower unit or would I have to use a thru hull with strainer???

 

[wolf21851]

Re: mercruiser 888, aftermarket closed cooling system

Are you saying you recently put this cooling system on?

Is/was the motor used in salt water?

Just trying to understand how it was used as putting on a fresh water cooling system on an engine block that has been used in salt water for more than a few months is generally not recommended and can cause further problems.

If at some point the engine was rebuilt and first completely sanitized then used only in fresh water you might be able to get away with it.

Mark

It was used in salt water, but rebuilt last year, cleaned out water galleys, new rings, bearings, cam, reseated valves, new valve guild seals, the works. still does the same thing.

 

[wolf21851]

Re: mercruiser 888, aftermarket closed cooling system

Thank you for the info. one more question, will the engine driven pump pull thru the lower unit or would I have to use a thru hull with strainer???

 

[MarkSee]

Re: mercruiser 888, aftermarket closed cooling system

... will the engine driven pump pull thru the lower unit or would I have to use a thru hull with strainer???

No one else has replied yet so I'm going to give you some input but since it appears you've added "the cooling system came off of another 302 with omc stern drive", seeing what the experts say is what is needed and we'll see how close I am.

First, is the cooling system a "full" system where the engine and exhaust is included or just partial? I think that may be important because if you read all the posts on the below thread, you'll see that an engine mounted water pump was specified for the "full systems and that a partial system should be ok using the alpha pump in the outdrive:
http://forums.iboats.com/mercruiser...nk-mounted-water-pump-vs-leg-pump-591374.html

But if you wanted/had to go with a Bravo style water pump, instead of the thru-hull as the entry point, there is a transom mounted water pickup assembly from Merc. Not sure if this is the same one Don was referring to in that thread but I did find part #88845A 1 and costing around $350:
WATER PICKUP ASSY (#88845A 1) - Performance Product Technologies

Whether you could use both inputs with a 'Y' fitting into the Bravo pump or would need to block off the input from the outdrive someone else would need to answer that.

Mark

 

[wolf21851]

Re: mercruiser 888, aftermarket closed cooling system

It is a partial cooling system. just cools the engine. raw water goes back out manifolds, no block off or partial block off plates to the risers.

 

[achris]

Re: mercruiser 888, aftermarket closed cooling system

How old is the exchanger? Was it PROPERLY cleaned out before putting it back into service?

 

[Don S]

Re: mercruiser 888, aftermarket closed cooling system

I would guess that the heat exchanger is probably plugging up on the antifreeze side. Usually from the rust and trash breaking loose on the inside of your blocks cooling system. Problem is, you can't get to it to clean it out.

Most manufacturers don't recommend changing to a closed cooling system after a year or 125 hours, which ever comes first. Your engine is 30+ years old.