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Antifreeze for Winterizing Recommendations

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I have a 2008 Malibu Sunscape 20 LSV with the 340 monsoon.  I'm winterizing it myself for the first time this year as the local shop prices have gone sky high. Looking at putting antifreeze in the block but I've noticed most of the available brands of RV/Marine AF, whether -50 or -100 burst protection, note that the product is not intended for use in gas engine winterization. They typically do state they are safe for all metal and plastics and have corrosion inhibitors.  I live in Minnesota and we do get temps potentially to -40 or colder so would like to use -100 to make sure.  I know West Marine sells a -100 that is okay for engine blocks but it's quite a bit more expensive.  Anyone have any thoughts on the brand, or is it all the same and the companies just don't want the liability of ruining an engine?  And how about sucking up the AF through the intake vs. pouring it through the hose?  Thanks.

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You could be like me and the 50%, according to this poll, on this site and just skip the anti freeze all together. My 98 is and has been dry stored every year since new... and is fine. Seems like too much trouble for not enough reward for me. But to each their own.




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Some antifreeze and some don't.  I say just do what gives you the most peace of mind.  If you do decide to use antifreeze though its important that you either:

1. first completely drain water out of the engine before you flush with antifreeze
2. I
f you don't first drain the water (I don't recommend this at all, but some do it this way),  you MUST bring the engine up to full operating temperatures to ensure the thermostat is open before you flush with antifreeze in order to make sure you are flushing out all the water in the block with the antifreeze flush.

Again, I highly recommend you drain the engine either way, and then decide if you want to flush with antifreeze or not.  Its not required, but it give some peace of mind - like cheap insurance.

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I don't, but if I did, I would just remove the plug on the top of engine next to the stat, opposite the ECM temp sender and use a funnel. I drain, then blow a shop vac into the tranny cooler inlet with the drain plugs still removed. Get an extra quart or so out that way. I also wet vac my mufflers out.

Edited by electricjohn
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Thanks for the input everyone. I’m definitely draining all the water out of the hoses/block before doing any AF. My local dealer charged me for “freeze protection” but I can’t seem to get them to return a call for advice on that. I know indmar doesn’t recommend AF—why would the dealers still do it on Minnesota?

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12 minutes ago, north40 said:

I know indmar doesn’t recommend AF—why would the dealers still do it on Minnesota?

My guesses: (a) it makes a customer feel like they are "getting something," (b) it's something to sell the customer (surely they are marking up the AF and charging an extra hour of labor to circulate it), (c) maybe it's easier to get coverage on a claim from the shop insurance if antifreeze is used (could also be a requirement).

Generally, my jaded view is that if the customer knows "winterizing" only entailed pulling four plugs and putting them back (as with the newer Malibu/Axis boats), it's harder to explain why that costs $500.

Now... on an 08 (which 99 times out of 100 is going to be raw water cooled) in MN (where I assume everyone has a heater), pushing some antifreeze through the heater probably is pretty prudent.

As others have said if you are DIY and it'll make you feel better when it's 10 below in a couple of months, do it. 

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I have the same jaded thoughts too Shawn. Our shops are $700 for an oil change and winterization this year. Doesn’t include vdrive/tranny fluid change. I’ll def put some AF in the heater hose. Thanks for advice. 

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For the heater my method was to disconnect both lines at the engine, fill one line with a funnel (half a gallon?), then blow that line out so that the AF goes all the way through and comes out the other hose. Tube inflator is good for that. 

Edited by shawndoggy
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1 hour ago, north40 said:

I have the same jaded thoughts too Shawn. Our shops are $700 for an oil change and winterization this year. Doesn’t include vdrive/tranny fluid change. 

:shocked: Anyone around Kansas City… I’ll cut you a deal and do it for $650

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I live in ATL GA, not super cold, last year we went down to 15 F which is pretty close to the lowest I have seen in 30+ years here.  

Pull the plugs, drain, put the plugs back in, and fill with 100 FP antifreeze (7 gallons from West Marine) using the flush fitting (2021 M6, the is a ball valve in the line next to the Sea Strainer that has to be closed) and Home Depot pump (info below), once the AF is coming out the exhaust (5-6 gallons) I pass what is in the catch bucket thru the motor 4 times.  This is way overkill but I figure if I am going to go thru the trouble going to do it the best I can.  The pump is 140 ish, this year the AF is 22 per gallon.

When I DIY usually spend some of my savings going the extra mile so to speak.  Don't save as much sometimes but the pump for example is pretty straightforward, can be used over and over, used also for pumping out the hot tub when needed.  I used the -100 instead of the next step up because when mixed with any water left in the system did not want to risk it not protecting low enough from a temp perspective.  That is what worries me, a pocket of water left because for example a hose is not routed right and so water did not drain completely.  

This approach saved me a couple of hours towing the boat and 250 at last years prices.  Since I have the pump and costs have gone up should save more this year.



West Marine AF info

Model # 363798 
MFG # 363798

HD pump info. Note on the pump, it is not high head so using a larger ID hose increases the flow a good bit, I used the larger of the typical garden hose sizes to ensure good flow.

Internet #303642270

Model #UTA02510

Store SKU #1002921354

Store SO SKU #1002836225

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