Usually on my 525 after I've changed the oil and run the engine on the hose I lay in the engine room and remove the blue drain plugs and also pull off the lower hoses to be sure the fresh water side is drained. If I fill the sea strainer with anti-freeze and start the engine and run a gallon of it though the engine will that sufficiently winterize the raw water system? Is it necessary to fog an engine on a boat that is stored indoors for 6 months? How do you guys winterize your 525s?

the complete fuel side needs to be proper laid up. heat exchanger needs to be drained completely. Oil cooler and all the water drained from the outdrive itself in which really is never discussed.

for the fuel side - search soup mix up here. That's what a lot call it in the industry,

I always service the drive too. This year it's coming off to check everything. I've never done anything to the fuel system. Sometimes I fog it directly through the spark plug holes and sometimes I don't. I have 3 cars that I put up for the winter too and I've never fogged them and they seem fine. I guess I should just drain the raw water side the way I always have by pulling all drain plugs and the lowermost hoses. I also take the batteries of the boat and cars into the basement.

I never fog. I would never do that soup mix. That's asking for trouble. I never put antifreeze in the raw water side. But I store in a heated garage most of the winter. The inside of every part on that motor looks like new. A really good injection guy said not to do oil mix or fog.

First would like to know all your problems and troubles along with experience you had using the soup mix for lay up. Less see - fresh fuel - double dose the correct amount of a fuel stabilizer and a 50 to 1 quality syn brand 2 stroke motor oil all mixed in a remote fuel tank in which you run the engine on for x amount of time for lay up ?. How in the world is the positive factors out weighed by any neg factors here ? I would not do the 10 to 1 oil mix Merc recommends. That's too much oil. But will add what I know. North Texas boats lay up for 5 to 7 months here winterized.

One is never use fogging oil for EFI MPI engines period - Map sensors hate fogging oil plus any other sensor that gets coated with it. Also if one has DTS throttle applications - you prob cause some harm to it by using fogging oil. . Have no idea why anyone would even fog thru the throttle body and even a carb app. One basically is you are coating the intake runners in which causes turbulent air flow when the deposits are formed especially over years of using fogging oils. Also it leaves deposits on the valves -- over time heavy deposits. Second it fouls out the spark plugs. Third it does nothing for the fuel side of anything.

Anyways Volvo Penta has done years of testing different ratios and the 50 to 1 soup mix in their engines plus none at all. Also Volvo redid a lot more testing when the CAT engines came about. The testing and results even tear down studies the engines always seemed to come out better especially on the complete fuel side when they studied plus commissioned.. I do know for fact all fuel systems last longer when the soup mix is used. The Gen 3 cool fuel and the Volvo carter fuel cells by fair have less problems with a 25 to 50 to 1 soup mix. I have torn into many. I also have torn apart mechanical fuel pumps and the difference is a lot. Today fuels do not offer any lubricity plus they can be corrosive along with when fuels evaporate leaving heavy varnished like deposits. Keep in mind the 2 stroke motor oil never evaporates and when mixed into the fuel -- that also slows down the evaporation of the fuel. I have tested this myself as well.

My experience prob 3 to 4 thousand boats laid up this way without problems period. Our area has had complete drought for years many boats did not move 2 to 5 years periods. I had boats winterized / laid up longer than anyone outside the area because of the area drought. I know for a fact the ones I laid up faired extremely well especially on the fuel side. My experience is firsthand. I would not change a thing as to the lay up procedures. Keep in mind I test fuel injectors and I can tell the boat owners whom do not lay up their fuels to the ones whom do on a regular basis. There is a big difference. I know what I am talking here plus would not spend the time to report all this without firsthand knowledge. .

Also will add anyone leaving anti freeze in your exhaust side for lay up - well think about that one especially if you have hp 525 headers. Anyways said my thing here and will move on. Good luck

I've never fogged the entire fuel system with engine running. I have sprayed fogging oil into plug holes and cranked engine with plugs out. As far as winterizing the fuel system I've read a lot about that. My boat is stored indoors and uncovered but not heated. A boat stored outdoors under shrink wrap endures temperature fluctuations from sunshine during day and condensation at night. Anyway that's my informed take on it. I do need to eliminate freezing danger though so I guess I'll continue how I've been doing that which is to remove the blue drain plugs and also pull off a few lowermost hoses.
Bup, are you saying that leaving antifreeze in the headers can cause problems? Why would it as it has corrosion inhibitors?
edit: Nevermind, I see what you're saying about leaving any liquid in the headers. I would pull the drain plugs anyway. I just wonder about any water being trapped in the heat exchangers so I usually pull off some hoses which is kind of a pain in the butt.

After I pull low hoses off. I hit them with a shop vac

Interesting!

I just run about 6-7 gallons of the pink RV antifreeze right through the ears that go onto the drive pickup. I run the entire 6-7 gallons and then watch the exhaust to start spitting out the pink antifreeze and also watch the intercooler dump fitting to verify that its also spitting out the pink liquid.

Been doing it this way for a while now and have had zero issues (im in Michigan and store in a non-heated garage)

I suck up 5 gallons of automotive antifreeze about 70 % to 30% water through muffs. Pull lower water pump hose let block drain. Replace lower hose pull intake bypass hose connect hose with funnel pour in 100% automotive antifreeze fill block through intake. Open exhaust drains. Now pickled for any amount of storage. Just make sure to run on hose and flush out all antifreeze in spring Prior to launching boat.