Sea Suctions or Keel Coolers

[Boasun]

Here in the southland of the USA practically every comerical vessel uses keel coolers. Two advantages for them are you are not sucking in sediment & other scud, and you don't have sea strainers to clean all the time. You have a hump on your hull that may be slowing you down about a quarter knot more or less. One boat I saw, was using about two feet of copper tubing, sticking out along the hull in a hair pin shape, for its generator's cooling coil. There are comerically made hull coolers that come in all shapes and sizes.

With Sea Suction, you may have a sea chest where the main, generator and fire/wash down system draws its water. Hopefully you have heat exchangers and are not sending raw water through your engines. But you still have to have sea strainers and those heat exchangers have to be cleaned every now and then. But you don't have a hump on the bottom of your hull adding to the hull friction of passing throught the sea. Also with sea suction you may have that sea chest or a separate hole through the hull for each piece of machinery that needs cooling...

Most sail boats have sea suction... But what would you prefer?

[Ilenart]

My yacht has keel coolers installed, approx 1 inch diameter pipes in a set of three. Works fine, the setup is 29 years old and still working no problems. My mechanic said he sees a lot of keel coolers on fishing boats.

Note that I still have a raw water inlet that cools the gearbox and then is injected in the exhaust manifold. The manifold had to be replaced a couple of years ago, however I would'nt expect much more than 5-10 years given the combination of hot gases and seawater. This also supplies water for the washdown, generator and sink.

Disadvantages are more maintenance with scraping / sanding down the pipes, priming and painting. Can be difficult reaching the top of the pipes and I guess they will eventually wear out and need replacing. Never thought about the drag from the pipes, however my boat has a sail area of 1,011sq ft (SA/disp of 17.2) and a 98HP diesel so reaching hull speed has never been an issue / concern. Also compared to the drag from my keel it is probably pretty minor

Found this photo that shows the pipes.