Yea seal weld channels to the INSIDE bottom of the boat and let the actual HULL be a heat sink. Aluminum is a great conductor of heat to with a few channels for water/ coolant to flow through and a raadiator it should stay cool. I also suggest an electric cooling fan to pull hot air out of the radiator.

The hotter coolant runs through the channels on the bottom of the boat. The cool water underneath will help the coolant disperse heat..... pretty simple..kinda like putting a can of beer in an ice chest. the hot beer will soon become cooler.

I built a old school mud boat with a 454 and had it set up like this, didn't need the radiator tho.

Nice. It will be alot of experamenting. You want the motor to run at operating temp. Not too hot or too cold.

I have a recipe some where on how much cooling surface needed, I added more cooling surface and installed a thermostat!

Lol that is so far off what a heat sink is, a heat sink is a device usually aluminum and wrapped in copper, it absorbs heat and then the heat disapates through air it a fan, its used to protect other devices or components for overheating. The whole beer in a cooler is more like what a radiator does. It makes hit stuff cold. A heat sink keeps heat sensitive items from failing due to overheatin but only to a certain extent

Yeah you are right about heat sink having cooling fins. I have one of those with external and internal fins to keep my power steering fluid cool in my rock crawler. I have it below my Radiator fan so its always having air pushed over it. The movement of air facilitates the cooling effect along with the aluminum dissipating heat.

I guess what I really explained erlier was kind of like Keel cooling to an extent... I guess

Exactly, lol if anything you explained a ?cool sink? The beer being the cool sink and the cooler well... The cool. But I still don't know about the whole Chanel thing on the bottom of the boat, maybe if it was sealed off and had like some sort of low profile high speed pick up the end of it, but for reliability and longevity purposes I wouldn't think anything protruding from the hull or anything to "snag" on would be a good idea

Lol you know that actually crossed my mind, have the tubing on the inside like you're saying and the put a sub floor over the tubing but leave the back of the subfloor open and then do the high speed pickups to in the from of the boat at the bottom of the rake to flush the "clean" water over the tubing, and then some through hull deck dains out he transom to drain the "dirty" water, But then you need flotation with a self draining deck. Bet you could make it work with the new pd boats that have the flotation. That would eliminate the radiator and also be wicked awesome. Two birds with one stone, lol now all I have to do is solve world hunger

I would be interested in seeing how it is mounted to the frame.

What kind of adatation was done to the down shaft to make it fit into the carank on that motor. New shaft? Cut and weld?

Finally, for the exhaust....would have to be a ingenious weld job to say the least. Not much room, if any, to come out the back with the coils on the exhaust plate. Modified tuner? That is the one thing that would be most difficult to accomplish I would think.

If you have a truly closed sytem you just need it to circulate. BUT I think I read you still need to have some kind of water to cool the exhaust ports and that will almost have to be pumped back into the water cause you do not want trash or exhaust to mix with coolant.

The water flows around the cylinders and through the block to provide the cooling. There is a large cavity behind the cylinders that water is pumped in from the gearcase on a normal motor. The input would have to be wither through one of the heads, with the thermostats removed, or at the base of the block and re-circulated out of the heads back to a reservoir or radiator.

Maxxis, it is a closed system in the motor. Overall cooling is going to be an issue.

I somewhat looked it up, The thermostat is is needed just like in a vehicle for quicker warm up times Once its at Operating temp. then it opens up to allow the whole cooling to circulate. The only question people were concerned with was cooling the exhaust port cooling because water does exit the exhuast aswell above the water line IIRC. Unless modifications can be done to ellinate that and keep the systme like a vehicle. But another question rises. What is the operating temp of the motor? It gets Cool water from the sea thats usually never more than 100* ish on average... Heck car's run at 195-200* for a complete burn...You just need to match your cooling system to the needs of the motor.

I'm not 100% educated on Outboard cooling sytems.

The water encircles each cylinder over most of its length in the water jacket. Exhaust ports exit to the center and flow down to the tuner which is mounted in the midsection.(one problem I see by mounting on a MM frame.) We raced V6 Mercury engines for over 15 years, most of the time we took the thermostats out. They get rusty or sludged up and dont work eventually. I think with a closed circulating system they would have to go, just my opinion. We based all our jetting and EFI adjusting on exhaust gas temps. They are much more accurate than the temp sensors that come in the heads. Anything over 1240 degrees at the tuner was the danger zone.

searching through some old post and stumbled on this.

Did you ever go run it? video?