# Winterizing closed cooling small block Chevy MerCruiser inboards



## Gone Fishing (Jul 31, 2001)

Ive always taken the safe approach and placed 4 gallons of RV antifreeze in a bucket (three -50 and one -100). I take off the intake hose where it meets the hull seacock and place it in the bucket. I run the engine till the antifreeze starts to run out the exhaust while simultaneously shooting fogging oil in the carb. Although this seems like a pretty foolproof method, its not exactly cheep buying 8 gallons of antifreeze.
How do you guys approach winterizing these engines?


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## andy capp (Aug 14, 2002)

My friend, does esentially the same thing. He dumps antifreeze in a bucket. Then screwed a metal pipe to a plunger. He sticks the plunger on the intake, and lets the pipe rest in the bucket, and lets it suck away. That is how they do all 3 boats.


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## Gone Fishing (Jul 31, 2001)

Thanks Andy. I have a buddy with Crusader 350s with closed cooling and he just drains the heat exchanges as far as I know. Ive never tried that approach and am worried some water might get trapped somewhere such as the external water pump. I can buy a lot of antifreeze for the cost of replacing heat exchangers or water pumps. I just figured the boat yards would probably drain the systems rather than filling them with antifreeze but Im not willing to take the chance without knowing fully how to do it properly. Thanks for your input.


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## SalmonBum (Feb 28, 2001)

4-5 gallons for a single V8 is about the norm, 2 gal for a closed cooling system. You can get away with just draining the water, which some people do, but that doesn't stop condensation...... which leads to rust. You should drain the water before putting any pink stuff in the motor to keep the AF at full strenght. My buddys IB is set up with strainers between the water intake and motor. He pulls the cap off the strainer, fires the boat up and dumps in the pink stuff.


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## SalmonBum (Feb 28, 2001)

After reading your last post, it sounds like you have a closed cooling system, Yes? You shouldn't need more than 2 gallons per motor if thats the case. I drain my exhaust manifolds and Heat exchanger, then run 2 gallons of -100° thru the Impeller back into the the exchanger\Manifold. Cost me $13 which is priceless since it helps me sleep every nite thru winter without worrying


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## Gone Fishing (Jul 31, 2001)

Yup, closed cooling. Where do you get the -100 for $6.50 a gallon. Seems I paid $10 last time.


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## SalmonBum (Feb 28, 2001)

Tony @ Lapeer Boat service. Not sure if thats the normal price, but thats what I get it for .

I think the Napa in Algonac had some last yr for a good price.


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## andy capp (Aug 14, 2002)

Gone Fishing said:


> Thanks Andy. I have a buddy with Crusader 350s with closed cooling and he just drains the heat exchanges as far as I know. Ive never tried that approach and am worried some water might get trapped somewhere such as the external water pump. I can buy a lot of antifreeze for the cost of replacing heat exchangers or water pumps. I just figured the boat yards would probably drain the systems rather than filling them with antifreeze but Im not willing to take the chance without knowing fully how to do it properly. Thanks for your input.


Yeah I know my input really did not help much. Basically was just saying he does it the same way. Maybe if you find a better way I can pass it on to him.


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## Gone Fishing (Jul 31, 2001)

I think maybe the reason that I'm using 4 gallons when it only requires 2 is that my son is helping me by letting me know when he sees the colored antifreeze coming out the exhaust. Sounds like I need to get somebody to help me that is not color blind!  :lol:


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## waterfoul (May 18, 2005)

Speaking from years of winterizing my own and a ton of my buddies boats, 2-3 gallons for closed cooling. 4-5 for sea water cooled. The -50 doesn't have much in the way of anti-corrosive properties, so I really don't recommend it for anything metal (fine for RV applications with plastic hoses). The -60 has 3 times the corrosive protection and won't gell till it reaches -54 degrees. This is what you want in your marine engines. When was the last time it was -54 in Michigan?? The -100 stuff is WAY overkill for us here in Michigan and is basicaly a marketing ploy. Also, NEVER just drain the block and manifolds and call it done. They WILL rust causing you all kinds of issues. Plugged thermostats for one. You should warm up your motor first also... making sure the T-stat is open. Then drain the block/manifolds and run your antifreeze in till it comes out the exhaust.


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