half closed cooling system for a 1989 4.3 liter cobra.

I have cabin fever and I used to take out my 19 foot Islander with the 3 liter mecruiser motor even in January, mostly for close to shore brown trout fishing. Draining the water on the 3 liter unit is simple and fast. I now have a 4.3 liter and getting all the water out of the system seems much more complicated and time consuming. So I am thinking of installing a half closed or fully closed cooling system on the 4.3. I went looking online for systems and mostly what I found is for Mercruiser units for 1989, but not for Cobras. The earliest Volvo units are 1992.
Can I use a Mercruiser unit or a Volvo unit? Or will I have to go scrounching for a unit in an old boat graveyard? What are my options?
Any advice is highly appreciated

Not having ever done it, I would suggest don't over think it.

If system works for a 4.3 it will work for you. Can get a Merc or one from Mr Cool Marine.

alldodge said:

Not having ever done it, I would suggest don't over think it.

If system works for a 4.3 it will work for you. Can get a Merc or one from Mr Cool Marine.

Click to expand...

I thought so too at first, but when I looked at it a bit deeper ,it turned out that these systems come with hoses that are cut to fit certain manifolds and special seals to close of passages in the manifolds and other brand specific things. hence my question.

Your biggest expense and sizing problem is the heat exchanger. Takes engine with antifreeze and water heat and transfers it to the raw water system.

cyclops222 said:

Your biggest expense and sizing problem is the heat exchanger. Takes engine with antifreeze and water heat and transfers it to the raw water system.

Click to expand...

The expense is not what bothers me. A burial shroud has no pockets so I can't take my money with me.

The issue with using a Merc system is that the OMC uses a high mounted alter on the port side and the H/E mounting for the Merc may not fit. However Volvos from 94 up used the same high mounted alternator as OMC, so I think a system for a Volvo V6 or V8 will work on the OMC, they use a vertically mounted H/E on the starboard side.

Do a search of
marine closed cooling systems
On the web.

It's generally is not recommended to add a heat exchanger to a used motor, even a fresh water

A rebuild where the block is baked, hot tanked and flushed is OK. However I would still run an inline mesh screen on the heat exchanger inlet based on personal experience

Used salt water motors will have a build up of flaking rust in addition to rocks, sand, small shell fish in the water jacket. Fresh water motors will have the mineral deposits, rocks, sand and small shell fish.

You cannot clean out the glycol side of a heat exchanger, so any debris in the water jacket will plug up the heat exchanger

However if you pull the motor, you can pull the heads, get the motor on a stand, turn it upside down, and chuck up a 17" section of 3/16" steel cable in a drill and manually clean out the water jacket. I usually see about 2-3 cups of debris come out. The heads usually require a bore scope inspection, and an acid flush in addition to the manual mechanical cleaning.

OMC had a vertical heat exchanger with the expansion tank higher than the carb. The Volvo and Mercruiser units are mounted horizontal.

Any can work, even a generic heat exchanger mounted to a stringer with a remote expansion tank and fill line.

A raw water cooled motor uses the thermostat as a mixing valve and always has water running to the exhaust. This is done by the special marine thermostat housing with a half dozen houses attached to it

A half system always has the raw water running through the heat exchanger and then out thru the elbows and exhaust. The glycol side has a small bypass from the heads to the water pump inlet, and the thermostat is in a simple thermostat housing, that opens and closes the main glow thru the glycol side of the heat exchanger. A vent line from each head or highest system point goes to the expansion/deareation tank to remove air. There is a full line from the expansion tank to the lowest point in the hose going from the heat exchanger to the water pump inlet

A full system is a bit more complicated with constant glycol flow thru the exhaust, and the thermostat is again used as a mixing valve on the block and heads. There is usually 4 vent lines to a much larger expansion tank and some systems use 2 thermostats. Raw water is constantly flowing through the heat exchanger and out the elbows

San Juan Engineering is now Orca heat exchangers. They may have a kit

In not a big fan of Mr Cool

A half system for a 4.3 will most likely be a 4-pass 4" x 22" long bundle to a 5" x 18" bundle. The size will depend on the raw water pump flow rate you have available.

Monitor Products is one of the OEM suppliers

Good to know, I guess that's why they are on the expensive side....