I first put closed cooling in my Cigarette back in the early 80's after losing my first set of heads to saltwater. I lived in Chicago at the time but the boat spent winters in Florida. Only had 800 hp at the time. To be honest I didn't do the math as far as sizing but put in the biggest heat exchangers I could fit (6" x 30" ) knowing I would wind up with more power. I mounted them in front of the rear engine.

The expansion tank is visible on the forward bulkhead. This pic is from early 90's when I had 1000 hp blower motors ps they ran on 89 octane. Water temp would hold at whatever the thermostat regardless of speed.
I'll see if I can find some better pictures.

The benefits of closed cooling are way more than the lack or corrosion:

• Constant block pressure with glycol raises boiling point - helps control steam pockets
• Constant block temp
• Non aerated water in block removes heat better - see above
• Unrestricted water flow through oil coolers and exhaust

Later in life I did some more projects, all closed cooled.

I still have a pair of big heat exchangers at the shop. I'll post some pictures tomorrow.





Michigan City poker run

Hey Mark were you able to run a reg merc seapump on that setup or did it require a two or three stage pump?

At the time there really weren't any multistage around. I was going to build something but never got around to it. My other idea was a much larger sea pump and slow the rpm down on it.

I wound up lowering my transom water pickups so I had pressure at speed. I measured the pressure at the header feed tube. That's all that really matters with the closed system.

I am sure I lost a few MPH in the process. Today I would run either a multi-stage or bigger pump for sure. Also I would plumb the water system with 1 1/4 pipe (1 1/2" hose) instead of 1" (1 1/4" hose)

Great picture of a runaway dinghy navigating through the marina in the background......

I think it was being towed lol

I might have a similar heat exchanger to Mbams at the shop. How many are you looking for?

Thanks for all the info great project and many benefits. Thanks for the pictures. What do you think rhe percentage of people with high hp motors running closed cooling?

I keep looking at Bam's picture and I still can't see a runaway dinghy or a heat exchanger!

I really want to do this to my 1200hp blower motors I also hear you gain a bit of power and fuel efficiency

14 apache..........The flat plate exchanger (cooler) seems like a great alternative to the shell & tube exchanger typically used on closed cooling systems.
There many times less the size and many times cheaper............do you still operate with a flat plate exchanger?.....Seems the way to go since a hi perf
closed cooling system by Monitor or PPT is far more expensive and there backordered till spring.............any picture you can share?