Winterizing your Mercruiser

[Rick Stephens]

Not hard to add a drain to the inlet line for the oil cooler. I stuck one in a few minutes. Used #12 on this page. Part number 861505

 

[JASinIL2006]

Well I sure appreciate all the help and suggestions. I like that idea of putting drain petcocks in those hard to remove hoses idea, but finding the right sizes without restricting the flow concerns me.

[EDIT: I think Rick posted his picture above as I was searching for the same one, that I posted. I'm getting slow...]

This isn't mine, but is from another iboat user (I forget whose...). It's pretty much the same as on my boat. It's a Mercruiser Drain Insert. I've noticed no change in the boat's operation, but I have noticed fewer bloody knuckles when winterizing... I also saw something similar for the circulating pump hose on the front of the engine, but I can't find the link right now...

 

[JASinIL2006]

Oh, and I did find this... on Evil Bay. It's a circulating pump hose with drain insert. I think this one is for the 5.0/5.7L engine.

 

[Scott Danforth]

Im glad i simply added a heat exchanger and the VP PS cooler is self-draining with my current boat.

However in the past for winterizing the SeaRay with the 5.0/Alpha,

with the drive off.......I would pull the hose to the PS cooler off the T-stat houseing, run a bunch of 100 PSi air thru the hose and PS cooler to blow the water out the gimble end, then with a funnel, dump in a half gallon of -100AF, blow that out, then fill the line and re-attach.

mainly because I didnt want to contort my way back there.

 

[tpenfield]

A heat exchanger was a Godsend (for me) . . . just keep the coolant strength up and run a bit of AF through the raw water side and pull the HE drain plug . . . done :thumb:

 

[kirkll]

Im glad i simply added a heat exchanger and the VP PS cooler is self-draining with my current boat.

However in the past for winterizing the SeaRay with the 5.0/Alpha,

with the drive off.......I would pull the hose to the PS cooler off the T-stat houseing, run a bunch of 100 PSi air thru the hose and PS cooler to blow the water out the gimble end, then with a funnel, dump in a half gallon of -100AF, blow that out, then fill the line and re-attach.

mainly because I didnt want to contort my way back there.

So exactly what is a heat exchanger, what does it do, and where is it located?

 

[nola mike]

It acts like a radiator in a car. Engine is cooled with antifreeze instead of seawater. Most of the Mercs didn't have them (only the 3.7l afaik). Not sure if they were a Merc factory option or dealer though?

 

[Scott Danforth]

They are optional on iron blocks and standard on aluminum blocks

 

[Kubaat3lover]

Guys, dontcha think leaving empty block will corrode and rust inside?
Why not leaving antifreeze inside?
Usually I drain the block, then flush it via muffs connected to antifreeze, drain it again and leaving the block empty with the plugs ON after all.
But maybe keeping AF with rust inhibitor is better than empty block?!

 

[Scott Danforth]

Guys, dontcha think leaving empty block will corrode and rust inside?
Why not leaving antifreeze inside?
Usually I drain the block, then flush it via muffs connected to antifreeze, drain it again and leaving the block empty with the plugs ON after all.
But maybe keeping AF with rust inhibitor is better than empty block?!

this is covered in the manual, if it makes you feel warm and fuzzy to put antifreeze in your block, then using a funnel, pour antifreeze into your water jacket.

however the amount of flash rust you will get is nothing over decades of use.

also, attempting to suck AF up a set of muffs usually leads to a broken block and a burned impeller. which is why the manual very specifically states, after draining, prodding, etc. to use a funnel.

 

[Kubaat3lover]

I see, but why muffs usually led to burned impeller? I did it twice and never had problem , its the same as running on muffs...

take care

 

[JASinIL2006]

When you run your boat on muffs from the garden hose, you have full city water pressure (40-80 psi) pushing water into the impeller to help it fill the engine. When you are trying to suck it up using a bucket of antifreeze, there is nowhere near the same amount of pressure. That’s what can fry your impeller.

 

[Ps91Rick]

Wow.. this has been a very informative thread to read.. Thanks all!! I’ve got an ‘87 Cobalt with Mercruiser V8 and Alpha 1.. It never occurred to me to winterize it last winter. It was sitting in my insulated garage and water was sitting in the block. Yesterday I started it up for the first time this season with the muffs on and I was appalled at the amount of rusty looking water that came out of the exhaust for at least 10 minutes of run time.. Lesson learned.. I’ll be draining the block this winter and will try my best to pull the lower drive as well which I’ve yet to do - but it was recently serviced just before I bought it. So.. I’ll put this on my to-do list for each winter even though we rarely get freezing temps here in the high desert of Los Angeles county.

 

[Sterling Marine]

Take it to a shop and see if you can ask a mechanic to point out the drains,cooler, and hoses that should be removed. Pay them to pull the drive ask i if you can watch to learn to do it yourself. Tip the guy good. I've done this for customers many times and it pays off when they need a repair.

 

[kirkll]

Ok.... I’ve done some research on putting a heat exchange unit in a 4.3 mercruiser and have priced out the exchanger itself at around $650 . What would a shop charge to instal this system? Any ideas? Or is this something that could be done myself over the winter down time?

I recently found out I have an auto block in my boat that a previous owner installed. My thoughts were by installing a heat exchanger, it may increase the longevity of the soft plugs over a raw water cooling system. Your thoughts on this would be appreciated. Kirk

 

[nola mike]

You can't put a hx on an old engine, too much crap in the cooling system, you'd clog everything up. What's a soft plug? As long as the auto block has brass core plugs, you're good.

 

[tpenfield]

I have put heat exchangers on engines run in only fresh water. If the engine has seen salt at all, then not a good idea, as Mike said. To much rust scaling inside the engine block, once in salt water.

I installed (DIY) exchangers (aka closed cooling) on my 7.4L engines. The kits were about $1K each. The engines had 16 years (740 hours) on Lake Winnepesaukee NH. all fresh water use. If you decided to go that route, I would recommend flushing the cooling system with an oxalic acid solution to get rust out of the engine block before you add closed cooling.

 

[Scott Danforth]

Ok.... I’ve done some research on putting a heat exchange unit in a 4.3 mercruiser and have priced out the exchanger itself at around $650 . What would a shop charge to instal this system? Any ideas? Or is this something that could be done myself over the winter down time?

I recently found out I have an auto block in my boat that a previous owner installed. My thoughts were by installing a heat exchanger, it may increase the longevity of the soft plugs over a raw water cooling system. Your thoughts on this would be appreciated. Kirk

first, if your motor has ever been in salt water, there is a buildup of rust internal to the motor that will plug a heat exchanger in hours. so you dont put a heat exchanger on a motor that was used in salt water

you can do it on a fresh water motor, however best to pull the motor put on the engine stand and pull the heads to get all the crud out of the water jacket.

if you rebuild the motor with a new core, then definitely do it.

your best bet if you truly do have steel core plugs, simply pull the motor and spend the $11 on brass core plugs

 

[pacofortacos]

I put a full closed cooling kit on my old 96 Cobalt after several years of salt water use. I just added 2 big brass strainers going from the manifolds to the heat exchanger and cleaned those several times in the beginning. That was years ago now.
Best thing I ever did for that boat.

Since I only use the boat for 2 weeks a year and in salt water, sitting on a trailer, even after using salt away, was causing the motor to rust away internally - rapidly. One year (before closed cooling), rust hit a small port in the one head and over heated and cracked that head - salt water in the engine. Drained it, tore the heads off the that day, coated everything and towed it home at the end of the week.
Blew the rust out of the block with compressed air, replaced the heads and installed closed cooling.

It isn't a job for everyone but it can be done. And I would only do it by being able to clean as much rust out of the block as possible and putting new manifolds and risers on.

If he is going to pull the motor to change the core plugs, might as well unbolt the heads and blow out the block and replace the head gaskets and then he can do as I did. Should be easy to get most of the rust out when the core plugs are out.
Just an actual experience doing what everyone recommends not be done.

 

[isaacs]

I always drain and poke (my boat has five drain plugs). Following that, I put a five gallon jug of RV antifreeze on the swim platform that has a hose attached to it that feeds the muffs. I suck that through and I'm done.

Be sure to buy the high quality RV antifreeze that does not contain ethanol. The ethanol crap will do nothing to prevent rust. I never have any rust in my manifolds so I must be doing something right!