Merc 350 - Overheats when winterizing

[crwallaceva]

I have a 1990 Merc 350 magnum. I started winterizing last night. I have the DIY boat winterizer that is a 5 gallon jug with a "T" for both fresh water and antifreeze. Everything runs fine with fresh water and temp stays about 1/2 way on the temp guage. Once I cut the water flow and start the antifreeze flow, the engine warms up tremendously. <br /><br />Should I just pump antifreeze on cold start or should I pump fresh water until thermostat opens. <br /><br />I'm changing thermostat just in case. I did test it and it was functioning properly - obviously since the fresh water was keep temp at normal range.<br /><br />I'm also using -50 degree RV antifreeze which is recomended by Merc manual.

 

[Don S]

Re: Merc 350 - Overheats when winterizing

What drive do you have, and is your engine raw water or fresh water cooled?

 

[waterone1@aol.com]

Re: Merc 350 - Overheats when winterizing

It is important for you to run on the hose until the thermostat opens. Is the antifreeze jug higher than the outdrive ? Is the valve unclogged and antifreeze running down the line freely ?<br />Remember, if using muffs, the outdrive cannot suck the antifreeze, it has to flow freely to the muffs. Is the tank cap off or vent open ?

 

[edfresh]

Re: Merc 350 - Overheats when winterizing

I had this pblm two nights ago. The antifreeze is too thick and not under pressure. So I added 2 qts of boiling water to the 4 gallons of antifreeze and mixed it well. Then the drive was able to take in all the antifreeze easily. It drained the plastic DIY tank. I decided to then open all drain plugs and remove all hoses. All that flowed out was the antifreeze. Therefore, it worked properly.

 

[crwallaceva]

Re: Merc 350 - Overheats when winterizing

Don S - Alpha MR is my outdrive. It is not a closed system if that is what you are asking. Draws raw/fresh water from the drive through the engine and out the exhaust.<br /><br />waterone1 - Ran to engine temp was in normal range, water continously exits from the exhaust so I assume thermostat is operating while in boat. Out of boat test confirms the thermostat is working, although I didn't feel the hoses to ensure water coming on other side of thermstat was warm. Jug is higher - sits on swim platform just as I did last year with no problems and no kinks in hose to keep flow going. Cap is off the tank also. <br /><br />Am trying again tonight.<br /><br />edfresh - thanks for tips I may try that although it is warmer today 60 degrees - yesterday was 40 degrees<br /><br />Chris

 

[Don S]

Re: Merc 350 - Overheats when winterizing

A couple of things. <br />1. If your impeller is over a couple of years old, it may have problems pulling the antifreeze up from the pickups. If it was in good shape, it should work. They get a set in them after a couple of years and just don't pull the water up as well as when new. The water hose forces water to the impeller.<br />2 With a raw water cooled system that you have, unless the engine is above the thermostat opening temp (usually doesn't happen on the hose) there is a very good chance you will NOT get antifreeze to your engine block. Even with a new impeller.<br />If you want to have antifreeze in your block, run the engine on the water hose, then fog, then drain the cooling system, remove the thermostat and fill the block with 50/50 antifreeze mix (Not straight antifreeze).<br />3 You have an Alpha I drive, not an MR. The MR was a pre-Alpha designation. I was curious if you had either an Alpha or Bravo drive as the Bravo drive has an engine mounted raw water pump.

 

[muc]

Re: Merc 350 - Overheats when winterizing

Can anybody tell me the difference between a MR drive and an Alpha drive?

 

[Don S]

Re: Merc 350 - Overheats when winterizing

At a quick glance, the top cover will tell the story. <br />An Alpha I drive looks like this.<br />

<br /><br />R & MR drives looks like this.<br />

<br /><br />More complete information here:<br /> Drive ID

 

[waterone1@aol.com]

Re: Merc 350 - Overheats when winterizing

It's easier if you go to www.mercstuff.com then click on "how do I" then click on "know what drive I have". There are pics with measurements, and compatibility requirements between R, MR/alpha and alpha genII. If you need more info let us know.

 

[waterone1@aol.com]

Re: Merc 350 - Overheats when winterizing

I guess we were both posting at the same time LOL

 

[crwallaceva]

Re: Merc 350 - Overheats when winterizing

Well, I managed to get 5 gallons of antifreeze pumped into engine. I didn't do anything different. Temp still crept up when I switched from water to antifreeze, but never in the red, just close long enough for me to get it pumped in and fog the motor.<br /><br />i did replace thermostat, not sure if I should be using the 140 or 160 degree one. Also mine, which appeared to be original since the bolts and gaskets were a pain to get off. It was the brass 140 and the only one I could find was the stainless 160 in either Quicksilver or Sierra parts the Quicksilver kit was 807252Q5 and Sierra cross ref. to 18-3647, both of which are 160 Stainless versions. Anyway I put it in, but not sure if I should have stuck with the brass 140.

 

[waterone1@aol.com]

Re: Merc 350 - Overheats when winterizing

There are three different thermostat housings that were used on that engine. Design 1 and 2 call for a 140 t-stat. Design 3 calls for a 160 t-stat. Interestingly design 3 is supposed to be for the alpha1 set up, however I have found several design 2 housings on magnum 350 engines with alpha 1 drives.

 

[crazy charlie]

Re: Merc 350 - Overheats when winterizing

Dont worry about the temp climbing,thats what happens when you use that kit.I have used the kit for at least 8 years now and the same thing happens each time.The reason is because of the volume of the flow being decreased when you switch over to the antifreeze and also it goes from being forced to the drive with garden hose pressure to being drawn through a smaller hose.The only way around it is to remove the tstat when doing this as the directions on the kit read.The kit is great!!!!I highly recommend it!!!Charlie