Converting a 430hp 6CTA-8.3 Cummins to keel cooling

[MLC]

I am re-powering an Alaska gillnetter with a Cummins 6CTA-8.3 rated at 430hp. The 430hp model of this engine is only available in a sea water after cooled configuration, and for my application, a keel cooled engine would be better.

The stock cooling system pumps seawater (via 1-1/4" Jabsco, positive displacement pump) into the after cooler, and then into a heat exchanger (which cools the jacket water), and then overboard.

I was planing to use two keel coolers, one for the jacket water, and one for the after cooler, on separate circuits. I have been told that there are commercial boats "all over Alaska" that are configured for keel cooling, with the 430 hp model of the 6CTA-8.3. I haven't seen one, so if anyone knows of such a setup, I would be grateful if someone could give me some details.

I have the jacket water circuit figured out, but I am uncertain about the after cooler circuit. Neither the local cummins dealer, nor the vender that sold be the engine has been able to provide me with the necessary information.

I have consulted Walters Keel Coolers, through a Hamilton Jet dealer in seattle. They recommended a 6 tube, 8ft cooler, operating off of the stock sea water pump. I already have a 4 tube 12ft cooler, so to save money, I would like to use that instead of buying a new cooler.

I have only been operating my vessel for two seasons, so I have very little experience in these things. From what I have heard, Walters Keel Coolers is a requitable company, but I can't see how a keel cooler would provide as much cooling as a direct seawater system, without more water flow. Maybe the system The Walters Keel Coolers recommended, (even though it dose not provide as much cooling as the stock system) will be enough, but I can't afford to blow up the new engine, so I want to be sure it will work.

If anyone can help me with this I would be grateful.

I have attached a page with the specs

[FAST FRED]

A cooling system is usually sized to drop the engine Out water 20-25deg F.before it is returned.

Walters Keel Coolers is a good old company,and in AK waters cooling should not EVER be a problem.

IN The Carib , towing at 3K with 85F water and some fouling on the cooler is a different problem.

Most coolers are designed for worst case , no speed and warm water.

Over cooling is possible under most circumstances and there are by pass thermostats that will return the water at a correct temperature.

[baeckmo]

In order to compare the 6-tube cooler with your 4-tube unit, we must know the pipe diameter of the respective tubes, and the flow path. Primarily it is the wetted surface that counts, but the flow resistance and the resulting water velocity will determine the final cooling efficiency.

A rule of thumb is that the aftercooler needs about the same surface as the engine (including oil cooling).

[MLC]

Thanks for your input.

Both the 6 tube cooler that Walters suggested, and the 4 tube cooler sitting in the basement are single stem coolers, with 1in ID tubes. According to the specs, the output of the seawater pump is 63gal/min, (238 liters/min).

The cooler for the jacket water circuit is a single stem, 4 tube cooler with 10ft tubes.
The output of the jacket water pump is 85gal/min, (322 liters/min).

The expected speed of the vessel WOT is 15kts, without any fish onboard.

I think the sea water temperature of Bristol bay is rarely above 60 deg F.