ITT Standard Brazepac Heatexchangers

[RXBOT]

I suppose this will only apply to cruisers as racers would not want the extra drag. For people with inboards I would think it would be beneficial to have a closed loop cooling circuit through a heatexchanger externally located outside the hull.This way they can run antifreeze mixture all year. Eliminates running saltwater through the block, don,t worry about winterizing engine. Also antifreeze will not boil over as soon as fresh water. It was origanally developed in WW2 to stop tanks from boiling over in the desert. Obviously there will be drag and you need thru hull conections. But you have thruhull for raw water cooling. The above exchangers are quite compact and made from 316 ss. Since they are industrial designed for having steam on one side and water on the other (to heat the water) they are a quality product tho not designed spefically for marine use.

[Tartan34C]

What you just described is called a keel cooler in the marine business and is reasonably common in workboats especially steel workboats. The model you found is made of unsuitable metals for saltwater work and a marine version is a better choice if this is what you want to use.

In low temp water use you will find that ice crystals form in the strainers so a keel cooler is worth while but in yachts that is the only use because of the problems from increased drag. It’s a lot more drag then you think. If you want to sail in high latitudes a twin intake and strainer system so you can change to a backup strainer when ice crystals form in the primary filter is a better system.
All the best,
Robert Gainer

[RXBOT]

If 316 stainless is not ok with salt water all right we will get appropiate marine version. However I have some questions on the drag issue. I beleive a fairly compact unit will do the job. Now compare that to a !3 inch 3 blade prop?
Or what about towing a dinghy? In light air it might be a concern. On a displacement hull in strong wind or under power is that drag so important? Like a tugboat with a 50,000 hp engine its only going to make hull speed really no matter how far you push the throttle. Yet it could tow a huge payload at the tugs hull speed no problem.

[Rockter]

How do you cool your exhaust?
What if you take a blow to the externally-mounted keel cooler plumbing?
You do see them on inland waterway longboats where the amount of weed in the water makes the orthodox circuit difficult.
They are rare on a sailboat though.

[Tartan34C]

Originally Posted by RXBOT

If 316 stainless is not ok with salt water all right we will get appropiate marine version. However I have some questions on the drag issue. I beleive a fairly compact unit will do the job. Now compare that to a !3 inch 3 blade prop?
Or what about towing a dinghy? In light air it might be a concern. On a displacement hull in strong wind or under power is that drag so important? Like a tugboat with a 50,000 hp engine its only going to make hull speed really no matter how far you push the throttle. Yet it could tow a huge payload at the tugs hull speed no problem.

Stainless underwater doesn’t do as well as bronze. The issue of drag is up to you. Some people don’t mind it and to others it is unacceptable to have more then is absolutely needed. To me a keel-cooler has too much drag but I am willing to use a narrow blade three blade propeller. Of course drag is cumulative and that is to say you have drag from the keel added to the drag from the shaft added to the propeller drag and now you add the keel-cooler which has significant drag on its own. It adds up and I think in this case it’s too much but this is in the realm of opinion and as they say your mileage may vary.
All the best,
Robert Gainer

[Tartan34C]

Originally Posted by Rockter

How do you cool your exhaust?
What if you take a blow to the externally-mounted keel cooler plumbing?
You do see them on inland waterway longboats where the amount of weed in the water makes the orthodox circuit difficult.
They are rare on a sailboat though.

You use a dry exhaust and put up with the problems that go with that system.
All the best,
Robert Gainer

[Boasun]

Here in the southland of USA, we use keelcoolers on all of our work boats. Many times we will nose into a river/bayou bank and sit there with the engines running and with a keel coolers we don't suck mud into the heat exchangers. Also the waters down here will at times, have a heavy silt content and you really don't want it to settle out in the heat exchangers either. Therefore we use keel coolers.
The keel coolers can be designed with a minimum of drag. So there is very little speed lost if done properly.

[RXBOT]

What if we regard the original heat exchanger I posted about as a sacrificial anode. It's primary purpose to protect your expensive inboard engine. If it lasts a couple of seasons good enough. The reason is that that exchanger doesn't have to be outside the hull. It has 2 inlets and 2 outlets, one set for each medium (saltwater and whatever mixture is in the block.). However you do need another pump whether electric or belt driven. One thru hull must be below waterline for saltwater inlet. The outlet could be above waterline and or be used for cooling exhaust also. Comments?