How to Winterize an I/O Boat using Inboard/Outboard Kit, Step by Step Guide 

I don’t understand draining the block after you fill it with anti-freeze? I thought the point was to leave it full of anti-freeze during winter months?

Another general comment: The RV style antifreezes are rated by burst temp, not freeze temp. This means that they will start to get hard at a temp that is much higher than the burst temp. As in the -60 may get hard at +10*F. So I would use only the -100, or mix up a 50/50 batch of Sierra propylene glycol antifreeze that gives you freeze protection down to -26*F. You can go higher on the % of antifreeze and get up to -54* for extreme areas. Either the West Marine -100 or the Sierra PG/no tox are the best antifreezes to use in engine systems. The rest, are for toilets and the like!

Run the motor on raw water first up to temperature then drain your block And manifolds and sea pump. Then antifreeze. More peace of mind..

Just FYI (5 years later), plumbing antifreeze is completely non-toxic and biodegradable.

Good info in this. I have a 19 foot runabout. I am a pilot as well,was looking through your channel. Seems like we both chose the most ridiculously expensive hobbies we could find!

its that time of year again!

Some of those jugs are in in my garage - they came with the house - I may use them when I winterize my I/O next month

I thought part of the purpose of the antifreeze or propylene was to leave it inside for its rust inhibiting properties???

OK there is a better way to do it if you want to use AF. The problem with doing it this way, is either you have to drain the engine first, or remove the thermostat. On a cool fall day the thermostat may not open all the way and then the AF will go out the exhaust elbows, so the manifolds/elbows will be full of AF but the block may still have raw water in it due to the stat not opening. The stat must open for water to exit the block. Draining the AF after you are done defeats the purpose of putting it in in the first place. You drain to prevent freeze damage and use AF to reduce corrosion damage. The right way and the way Merc and OMC told you to do it in their shop manuals: Warm engine up, change the oil and filter. Run it again, check for leaks, and then fog it. Let it cool off before draining. Then remove every drain referenced in the manual and poke all drain holes with a pick or small screwdriver. Remove hoses as directed in the manual to drain the front circulating pump and p/s or fuel coolers. After all is drained, now your engine is freeze protected. If you want corrosion protection: Disconnect the large hose from the thermo housing to the front circulating pump on the top end. Put a funnel in it and fill the engine with -100 Marine AF, till AF comes out the neck of the themo housing. No need to remove stat. Re-connect that hose. Then disconnect each manifold feed hose (and elbow feed hose if your engine has separate ones) and fill with AF till it runs out the exhaust. Re-connect hoses. Now the engine and exhaust are full of AF. Lastly put the drive down and disconnect the hose going from the transom to the thermo housing (Alpha, Cobra) or impeller housing (Bravo, Volvo). Hole this hose up and fill with AF till it runs out the drive intakes. This pushes water out of the hoses going thru the transom mount and in the water passages in the drive. Reconnect that hose. If you have a Bravo or Volvo with an engine mounted impeller I would disconnect the hose that goes from the impeller housing to the thermo housing. Make sure the housing drains. Then reconnect it on the impeller housing, disconnect it at the thermo housing. Now fill the hose and housing with marine AF. Reconnect the hose. Now all the raw water is out, and everything is protected from freezing and corrosion. I would say, DO NOT use those winterizing kits unless you have a closed cooled engine with a heat exchange. If you don't drain the raw water first you could wind up with a cracked block, heads and intake come the spring. PS use the -100, the -50 or -60 starts to get hard at about zero F. Those ratings are burst temps not freeze temp. I measured the freeze temp of the -100 with a propylene glycol hydrometer and its about -45*F. More than good enough.

the most important part is to wait for the motor to warm up so that the thermo opens to introduce antifreeze to the entire system.

I think the reason your tank started to get crushed is you have to open the air inlet at the top of the tank.

If I may ask, why did you drain the antifreeze and not just leave it in there for winterization?

I use the same set up. But I have 4 gallons on antifreeze in the tank. I have the spark arrestor off the carburetor. I run fresh water until it totally warms up. Then I switch to the antifreeze tank and run it down until I see pure antifreeze coming out. Then I fog the carburetor down until it kills the engine. Then I'm done. I have never drained the block. I'm in north Texas area. But even with the hard freeze in 2021, I had no issues. I bought my boat new in 1997 and still looks and runs good.

I drain the block then re-install the butterfly plastic plugs.. then with a five gallon bucket with a hose fitting connected to ear muffs and the bucket on a ladder. I pour 4 and a half gallons inside the bucket while running of - 75 rv antifreeze and once pink is coming out of the drive. I then drain the block again of the rv anti freeze. I leave the blue plugs out and placed in a ziplock bag secured to the steering wheel. I reinstall the plugs at the beginning of the season… Previous I was installing the blue plugs once drained and I had a blue plug blow out over the winter clearly I did not achieve a complete drain down. .. I started the engine at the beginning of the season and water was pouring out through the blown out plug

Great kit and saves you from getting ripped off at the marina,lol

I can't be 100.000% sure, but it looks like you are using RV antifreeze which should be safe for potable water systems and therefore not poisonous. I still would not let my dog drink it but if they get a taste of it by accident I don't think it would be too harmful. You should not use regular automobile antifreeze, which is typically not pink. Pink RV antifreeze can be found in the camper area at Walmart. Also, would be cool if you could put a link to the tank/hose kit you are using. Thanks for the good quality video.

430 Celsius is 806 F , Fresh water engines should run at 170-210 degrees. You were not reading the thermostat temp or the water would have turned to steam at 100C or 212F

what's the point of running antifreeze through it if you're gonna drain the block anyway? Drain the block first and fill it with antifreeze after and leave it in there. In the spring drain it and save it for the next time

is there a link to the carb fogging winterize portion?

Once motor warm up. Faster to drain water out of block. Switch over to antifreeze. Then open drain to see it.

I see a lot of diluted antifreeze coming out of your drain blocks? I think too much human error is possible in this scenario? How confident are you that your engine block is totally drained ? I once saw the marine anti freeze being stored outside at Lowe’s lumber, and it was all Slushy on a 10° day 🤷🏻‍♂️🤷🏻‍♂️🤷🏻‍♂️

Why drain the antifreeze once in ???

great if you run in a lake, but you don't ever want to drain the block down if your in salt water.

Very good video. Thank you.

Just acquired a '78 Wellcraft Airslot II with a Volvo Penta 350. Can't see any other information on it, e.i, litres, etc. Have no documentation. Anyway obviously sea-cooled, but beyond that we are clueless on how to winterize. It does have antifreeze, but not sure what else to do. Will this method cover this particular engine? First time boat owners. And we live in Alaska, down by Homer, so the winters aren't as severe as in the interior (Fairbanks, etc.)

No reason whatsoever to fog an injected motor. It does nothing. If you were going to let your car sit for 3-4 months, would you fog it? No, and it's the exact same thing. Put some stabilizer in the fuel, put the antifreeze in the engine and forget about it.

Why infuse the motor with anti freeze just to drain it? Seems like a waste to me.

May be a stupid question but do you have to “dewinterize” your boat whenever warm weather rolls around again and you go to use it?

I realize this is an old video, but you mentioned OTHER steps, like carb fogging. You said it was in your other videos? Not seeing anything labeled that.

Do you need to remove the water engine plugs? Or does this kit pretty much takes care of thst srep since antifreeze is flowing through out the system?

So when you run the antifreeze through the engine and then open the blue plugs, you release all that antifreeze and possible water if trapped in the system, so do you leave the block/engine empty over the winter or fill it back up with antifreeze?

You need to open the vent at the top of the handle!

how much antifreeze did you use ?,,I have 3.0.

Thanks Great video

And FYI RV antifreeze is NON toxic. However that being said I would still not want a human or pet to consume it.

Can’t you just leave the antifreeze in the line over winter?

Is it better to just keep the antifreeze in your system or drain it through the frost plugs?

Where can I buy this kit? Canadian Tire?

I just used this system and totally failed. I can't figure out what happened. I shut off the water and opened the antifreeze valve. It started to flow fine then halfway down seemed to stop flowing. I figured it was vapor lock so I cleared the vent hole. Never did I see antifreeze coming from the exhaust port area. The motor started getting hot pretty quick so I shut it down. I put another gallon of antifreeze in the tank, punched a bigger vent hole in it, raised it even higher than the first time and tried again. It drained all the way but when I drained the block it looked like clear water, no antifreeze. What the hell? The boat is in perfect condition and everything was working fine while running on the hose. I ran it for 20 minutes before opening the antifreeze tank so it was plenty warm enough for the thermostat to be open. I don't get it. Any ideas? Thanks.

Anybody know if I can use the same system on my inboard ski boat? I have a boot that fits over the raw water intake on the hull bottom (some people call the boot a "fake-a-lake).

I would hope it would have a long block in it or it would never run lol

Helpful video thanks . Does the Rv Antifreeze have anti corrosion properties in the same way that engine coolant has? Is there a reason to not use engine coolant ?

lots of hands on know how from smart people

why don't just leave antifreeze in there? How many gallons did it take ?

Rv antifreeze is not poisonous.

Tried this tank blew up and covered deck in sea brute camco says my fault cause I pressurized the tank ok how did I do that cause I followed this vid cost me 75 bucks for kit anti freeze and two hours clean up still don’t know how I failed maybe will vid a fail and post to RU-vid use caution cause this thing is delicate camco has no support they suck beware is my experience kaboom.

Th would be easy to make Dave

I just pull thermostat out

Did put plugs back in or leave them out?

How many gal did used? Hold up to 5.

Is there a way to winterize without engine running

$40 for a new thermostat meter 3 wires ..take 20 minutes to replace..

Appears to be the wrong kind of antifreeze...that looks like waterline antifreeze which has ethyl alcohol in it...you need to use propylene glycol. Usually much more pink in color... The Prestone bottle says, "NOT FOR USE IN ENGINE BLOCKS".

Not sure the point of winterizing if you’re just going to drain it. Unless you’re living in extremely cold climate.

That's not the rait way to do it

Poke a hole in that supply tank!

Don’t put video up when you have current problems with your engine that have not been corrected and or addressed

Your water looks very diluted

What a mess lmao