Mer 350 mag closed cooling. NEED HELP

[z284u2try]

Well I just found the forum and have been reading for a few days buts till can't answer my questions. Maybe some of you merc guys could help me out. My parents bought a new splendor deck style boat with a merc 350 efi mag/bravo 3 close cooled. I have no experiance with close cooled. Long story short got real cold here the other night and it started to freeze up. I checked on it that night and pulled 3 drain plugs that are blue no water drained. I could feel ice in the holes. That night I put a heater to it and covered the engine with a blaket. Next day was nice and warm I put the plugs back in and started her up let it run for about 10 minutes on ears and fresh water. Got to about 170ish temp and no bad signs that i can tell. I hooked a pump up to the ears and in a vat of 50/50 antifreeze and pumped it all into the engine via the ears and cut it off. Could someone tell me how the closed cooling works and if you think I winterized the boat correctly?

 

[Haut Medoc]

Re: Mer 350 mag closed cooling. NEED HELP

Welcome to iboats
The year & serial # (if possible) would be helpful.....
The internals of the block & heads are fine as long as the closed side of your system has the proper mix of anti-freeze...(50/50) is optimum.....
A closed system is very much like an auto system....
The difference being that instead of having a radiator that is air-cooled, a boat has a 'heat exchanger' that is water cooled.....
It looks like it has a radiator cap.....
Inside the heat exchanger are two sides-
The closed side & the raw water side.....
The engine sucks cooling water from whatever water you are in & circulates through the exchanger ...
The closed side circulates the water/af mixture in a closed loop, just like a car & tranfers the heat from closed to raw side which is then exhausted through the 'elbows' & overboard......
Without knowing what model you have, I can't give you the proper procedure for your specific model....
It would be good to remove the raw water feed that goes to the exchanger & drain it......
The power steering cooler is generally between where the raw water enters the boat & the above mentioned hose.....Make sure both are drained....
Hope this helps.....Haut

 

[z284u2try]

Re: Mer 350 mag closed cooling. NEED HELP

Hey thanks for the Welcome and the explanation of the system. reminds me of a air to water intercooler for forced induction cars. I don't have the serial number for the engine off hand but it is a 2005 350 mag merc with the exchanger sitting top front of the engine. I pulled two fresh water feeds that went from the risers to the exchanger. If the engine block is cooled with anti freeze how could the blue plugs I pulled have fresh water/ice in them. One was pulled from the bottom front and two from the bottom left side of the engine down low if facing it? I am worried the mix in the closed cool is not doing its job. My parents did the air pump deal before I put the plugs back and pulled anti freeze from the lower unit. I want to apologize for all of my questions as I am a car guy and a newb to boats but want to learn. when I started the boat lots of water came out of the hull drain I don't know from where. I turned it off and relized the air system deal has the 2 green indiacters up I released the air valve and restarted and no more water drained into the hull from the engine. Could you tell me how the whole air pump system works. I see 4 small air tubes these little lines are suppose to clear the fresh water side of the engine?

 

[Haut Medoc]

Re: Mer 350 mag closed cooling. NEED HELP

Your engine is too new to be familiar to me, unfortunately..:'(
But there are many here with more knowledge than me....
So stick around & you will get the answers you seek...
If you are serious about doing maintenence yourself, you should look into getting a service manual for the boat........
The serial # should be easy to spot while looking at the engine.....
Don't waste your time & money on a Seloc or Clymer's...
Get the real McCoy- Mercruiser.......

 

[z284u2try]

Re: Mer 350 mag closed cooling. NEED HELP

This engine came with a manuel it seems very deatailed but lacking at the same time. Form reading it the air pump metod seems strait forward. Pull one blue plug and pump until the green indicaters pop up. Thank you for the help. I think at this point I am going to start pulling hoses and filling everything with a 50/50 mix and roll with that. I told the rents just to take it to the marina and have them do it. But the whole reasom they bought the closed cool is so they can winterize it. This boat is only used in freash water.

 

[Haut Medoc]

Re: Mer 350 mag closed cooling. NEED HELP

Don't start pulling hoses, simply take the radiator cap off & check the af/mix with a tester, (while cold of course).....
If you followed the directions that came with the owners manual you should be OK.....
It is possible that you could damage the engine if you start pulling hoses & pouring 50-50 in.....
Unless you are looking at a hard extended freeze immediately, I urge you not to follow that course of action....
If nothing else keep the heater & blanket on it and wait for a more informed answer than I can give you.....
Furthermore, you should help your parents out & save them a few bucks with a little effort on your part....
Especially if you use the boat......
I am sure it won't kill ya & they will appreciate it......

 

[z284u2try]

Re: Mer 350 mag closed cooling. NEED HELP

Well Looks like not much traffic here. Thanks for your help. I am going to roll with what i have i believe it should be fine.

 

[Don S]

Re: Mer 350 mag closed cooling. NEED HELP

In the past few years, Mercruiser has come out with some new drain systems. Trying to explain what and where to drain them and get it done safely is almost an impossiblity. If you have the air actuated system, then you shouldn't have to remove any plugs. That is unless the system doesn't work or a hose is plugged up somewhere. You have no way of knowing. Assuming you have the new Dry Joint type exhaust manifolds and risers. I have also seen severaly setups from what is actually shown in the service manual. So it would actually be impossible for anyone to give you an exact answer on how or what to drain.
Short of understanding the system and following the raw water path and determining if that section is drained or not,

 

[z284u2try]

Re: Mer 350 mag closed cooling. NEED HELP

I didn't trust the air actuated system so my end all decision was to pump a/freeze into the engine via lower unit after she was warmed up and visually verified that it was good by checking a all blue plugs I found and cracking a few fresh water hoses. From my understanding the block is cooled with a/freeze from the closed cooled system.