View Full Version : Closed Cooling/Radiator

07-09-2014, 11:34 AM
I am going to re-power my 14x58 Sumerset that has one mercruser engine. Instead of using raw water I was going to use a heat exchanger. When I was talking about this one of our maintenance men spoke up and said use a radiator instead. I got to thinking and seems I remember a houseboat with a radiator mounted beside the engine. I looked online but either did not use the right keywords or this is not done?
Can anyone enlighten me?

07-09-2014, 02:09 PM
The heat removed from the engine via the radiator would have to go somewhere. A conventional radiator is a water to air heat exchanger. It will not work in the confines of your engine compartment. You need a water to water heat exchanger. Why do you want to go closed cooling? What are you trying to gain?

07-09-2014, 04:33 PM
I'm with East TN. Water is a lot more effective at removing heat than air would be, even if you had good air flow. That's why a 60 degree day feels pleasant but jumping into 60 degree water will take your breath away and might cause hypothermia if you don't get out soon enough. Since you don't have good air flow, a radiator isn't a good bet for a boat.

The only reason I can think of for using a closed cooling system would be to keep salt water out of your engine block or perhaps to make winterizing easier. I tackled the winterizing issue for my ski boat with a series of hoses and ball valves mounted remotely from my boat engine. I can winterize that boat in about 30 seconds and don't even open the engine compartment to do it.

If you're in salt water, I would think about a closed system. There are two types. One uses recirculating coolant to cool the exhaust manifolds as well as the engine block. It will give you the full advantages of a closed system. It will also give you the full brunt of the cost of a closed system. More common is a so-called split system. It uses recirculating coolant to cool the engine block but raw water to cool exhaust manifolds.

If your boat is in fresh water, you will likely prefer raw water cooling.

07-12-2014, 10:01 AM
Are you in fresh water or salt?

07-14-2014, 11:58 AM
Fresh water.. going to marina where the boat is at I thought had factory closed loop radiator cooling.. will take pics if I was not seeing things and the boat/owner is still there. I have been thinking about it and I agree does not seem reasonable to get that much heat out of the bilge area without using water. May be a split unit as the professor said.

07-14-2014, 12:25 PM
My boat has split units on both engines and the generator. The blocks are cooled by the closed system - with keel coolers as the heat exchangers. The water pumps on the engines circulate the coolant (water/antifreeze mix) through the keel coolers just like a car does through its radiator. Each engine also has an external belt driven water pump that supplies water to the exhaust manifolds and risers. The previous owner built it that way because he ran it up and down the Cumberland River - said it was safer that way.

07-14-2014, 07:48 PM
If your in fresh water, raw water cooling is the way to go. Unless it's REAL muddy.

07-18-2014, 04:20 PM
I'm not sure a radiator is even legal, except maybe on an airboat.

08-19-2014, 07:19 PM
If you use a radiator you have to use "Dry Stack" exhaust. A big problem in and of itself.

08-20-2014, 10:43 AM
My twin Crusader 350/270 have OEM closed cooling. River water is pumped with a belt driven pump through a heat exchanger for the v-drive and through a heat exchanger for the engine . River water is exhausted through the engine exhausts. Antifreeze solution is circulated through the engine and the other side of the heat exchanger in a manner similar to an auto engine/radiator config. So, engine is protected from corrosion by the antifreeze. Never had any problems except to remove impeller fragments from the face of the tube bundle of the heat exchanger.

09-18-2014, 08:22 AM
Going to look at something like longjohn has

09-18-2014, 08:52 AM
Longjohn has described a pretty standard split system. It's the same thing that East TN described in his boat. They use recirculating coolant in the engine block and raw water in the exhaust manifolds. There isn't a thing wrong with them except that the cost is likely overkill unless you boat in salt water, brackish water, or really muddy fresh water.

09-18-2014, 09:23 AM
I understand and will look into the cost/time/complexity. I am pretty sure I am yanking the old Mercury 228 TR out and replacing it with a new/ newer motor/out-drive..IF I can afford it (think I can based on a rough quote by neighboring marina). My goal is to not have to worry about the engine for another 15 years, outside of normal maintenance. When I turn the key it starts is major. I feel those are reasonable goals. I may be over-thinking this as the present engine is a 1977 and only went out after the ex did not winterize it. It just makes me shutter to think of raw water being in the engine but again this is normal for all outboard/inboards. So I answer my own question / thread I am overthinking this.

I work in metals so welding a new transom plate is easy and I can have it cut with a water-jet to fit a new engine pattern.
Is there anywhere on the web that has used engine/out-drive combos?