Mercruiser 5.7 cooling question. ***Updated with pic**

[RandyBC]

This is probably a stupid question but is a 2001 5.7 Mercuiser carburated engine with Alpha one sterndrive a "coolant" model or a "raw water" model. I see in the manual that both have raw water referenced. How does one tell the difference? I'm trying to determine the locations of the drain plugs on my engine to remove sea water prior to winter storage and there is a difference between the two in terms of number and location of the plugs.

 

[86 century]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

One is cooled directly by the water pumped from lake/river/ocean through the eng will be referee to as raw water or sea water.

The other uses a heat exchanger pretty much the same as the radiator in a car other than raw water is pumped through to remove the heat.

If you have a coolant tank or anything that looks like a radiator cap you have a coolant eng most of the time they are referred to as a closed cooling system.

 

[Don S]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

Post a picture of your engine, that would make it very easy to figure out.

 

[RandyBC]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

Thanks. I have a closed system. With a closed system, since there is no seawater in the engine block, is there less potential for catastrophic freeze damage such as a cracked block?

 

[Don S]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

As long as your antifreeze is good for as cold as it gets in your area, you should be fine with the block. BUT, do you have a full or half closed system. The full system includes the manifolds, the half does not. Then you drain the raw water side of the cooling system.

Since you don't really know what you have, it's tough to give specific information.

 

[RandyBC]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

The manual shows manifold drain plugs (2 of them) and one drain on the low port side intake hose. I'm going on a mission to find them today.

 

[Don S]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

You won't have manifold drains if they are part of the closed cooling system. While you may be looking at your manual, you could have an aftermarket setup the manual doesn't show. You are looking at messing things up if you don't know what you are doing.
Post some pictures of your engine so we can see your cooling system and how it's set up.

 

[RandyBC]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

Thanks Don. I will try to post a pic today. There is a large heat exchanger on the front of the engine above the serpentine belt. The manual that came with the engine (gasoline engine alpha models) has a section for draining the seawater section which is described as:

1. Level engine
2. Remove drain plugs from bottom of exhaust manifolds
3. Remove draim from port seawater pipe (lower left side of engine when looking back to front)
4. Remove end caps, sealing washers and gaskets from heat exchangers.
5. Clean drain holes with stiff wire.

 

[RandyBC]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

So, undoing all the drains emptied the engine coolant. I did think it strange that when I emptied the manifolds that the coolant overflow reservoir also emptied. I asked service dealer who felt that the engine was plumbed so that the manifolds were cooled as well. I'm just going to send coolant in through a 5gal bucket with muffs and call it a day.

 

[Don S]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

Your manifolds are probably cooled with antifreeze as well. Post some pictures of your cooling system showing all the hoses. Then we can help you figure out how to drain it properly.

What is your engines serial number? Year doesn't mean much, Mercruiser goes by serial number and SN range on things, not year.

 

[RandyBC]

Re: Mercruiser 5.7 cooling question.

Re: Mercruiser 5.7 cooling question.

Thanks Don. I will post pics when I figure out how. My merc's s/n is 0m070881

 

[RandyBC]

Re: Mercruiser 5.7 cooling question. ***NEW pic added.

Re: Mercruiser 5.7 cooling question. ***NEW pic added.

I finally figured out how to post pics. I hope this works. My merc's s/n: 0M070881

 

[RandyBC]

Re: Mercruiser 5.7 cooling question. ***NEW pic added.

Re: Mercruiser 5.7 cooling question. ***NEW pic added.

Don?? Also, can I confirm that the engine is a 2001 from the s/n?