Engine draining question

dvan1901

Chief Petty Officer
Joined
Mar 26, 2006
Messages
503
I have a 2007 Mercruiser 5.0MPI with the multi-point drain system. I Keep my boat in the water, but it is supposed to get near freezing the next two nights so I would like to drain my engine block; I wasn't planning on pulling the boat out yet; so, my question is, can I drain the manifolds and block while the boat is still in the water without flooding the bilge area due to water continuously coming in? I was planning on pulling the hoses at the manifolds and block, and not using the blue plugs (don't trust them). I do not have an intake shut-off valve (yet). Make sense?
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Engine draining question

I was planning on pulling the hoses at the manifolds and block, and not using the blue plugs (don't trust them).
That's a great idea. Since the single point system will only work until the engine starts making rust then it will CAUSE you to have a cracked block/manifolds.

It depends on where your water line is compared to the engine. You might have a continuous flow of water since most engines are sitting slightly below the water line. The only way to prevent it is to put a shut-off valve in the raw water line from the transom.

If it's "near" freezing at the water, it won't cause a frozen block over night.

It'll need to be well below freezing to freeze an engine that is "on the water".

Now, having said that I would be worried too since "near" freezing can frequently be "below" freezing. [When do the WX people EVER get it right??:rolleyes: ]

You could probably add a valve to the raw water hose from the transom using a Sched 40 PVC ball-valve. That way you can turn it off. Bad thing is that if you do get a (real cold) snap freeze you could break the valve and flood the boat.

This is all so academic.......If it's only going to get to say 28*F tonight, you're probably safe. If you have power get one of those heaters designed for this purpose. (But I wouldn't rely on it for a cold winter.....power goes off sometimes !)


If it were me......I'd pull the boat and call it quits for the winter.

YMMV as it were....


Regards,


Rick
 

dvan1901

Chief Petty Officer
Joined
Mar 26, 2006
Messages
503
Re: Engine draining question

I pulled it and drained it, just to be safe. Only for a few days then it is supposed to warm up again. I am planning on having a valve installed on the intake side so I can not worry about it; not a pvc, but brass.
 

Bondo

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Apr 17, 2002
Messages
71,116
Re: Engine draining question

I am planning on having a valve installed on the intake side so I can not worry about it; not a pvc, but brass.

Ayuh,... If you insist, use Bronze, not Brass....
But,...
It's Totally Unnecessary,... draining the motor will not flood the hull,...
We're talking only a couple of gallons,... It won't keep flowing in...
with the multi-point drain system.

Glad to hear you Don't trust it,... Those are a Sure Bet for a Cracked block eventually....
Drain plugs, At the drains are the Best way to go....
 
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