Hull mounted heat exchanger?

[Red Rider]

I am going to build a hull-mounted heat exchanger on one of my boats that will be used in shallow water. The engine is a small block 350ci Chevy powering a jet drive. The original setup used raw water piped from the jet pump for engine cooling. As the boat is now used in brackish/Salt water I want to change the cooling to a closed system and use a hull mounted heat exchanger. As the engine going in is a late model Vortec with thin wall casting around the some of the water jacket areas, raw water-cooling is not an option that I want to use.<br /><br />I have two pieces of 8 foot long Stainless Steel pipe/thick walled tubing, I.D.=2.200" & O.D.=2.500". (This pipe was salvaged from an Ammonium Nitrate system so it is weld able and highly corrosive resistant).<br /><br />Does anyone know how to determine how much surface area/feet or whatever I would need?

 

[18rabbit]

Re: Hull mounted heat exchanger?

No, I know almost nothing about the things but I have two such critters on my boat, one for the engine and one for an air conditioner. The hull is designed with recesses that the exchangers are fitted into. This protects them from any large debris that should smack the hull, like when I run over a jet ski.<br /><br />From memory (and a few old photos), the exchanger for the a/c is four tubes, each about 5 or 6-ft long (20 – 24ft total) and about ¾-in O.D. including the fins. The exchanger for the engine (Cat 3208T) is six or 8 tubes, each about 10-ft long (60 to 80-ft total), 1½-in O.D. with fins. The hose to/from the exchanger manifold for the engine is 2½-in.<br /><br />A few things to think about: (1) tube material, ss may or may not be appropriate. Different metals transfer heat differently. The a/c exchanger is made of copper (I remember it being green ). I’m thinking the one for the engine is too but I can’t remember. (2) Length of tubes, I’m guessing 16-ft may not be enough. (3) Diameter, the bigger the bore, the less heat is exchanged. You want surface area verses capacity. 2.2-in I.D. may allow too much hot water to pass without being exposed to enough cooling surface. (4) Fins, they make a world of difference in pulling heat out.<br /><br />Perhaps you can research an after market product that is designed appropriately for your engine then work backward into duplicating it with the intent of doing some major hull work to recess it appropriately. Maybe cleaning a strainer is not that bad of an idea. Just some thoughts…

 

[Elk Chaser]

Re: Hull mounted heat exchanger?

You are talking about building something that should be engineered to a specific set of specifications (ie: tubing size, water flow on both sides, materials, etc.) You would be shooting in the dark and the likelihood of getting it right is very slim.<br /><br />Trying to build one yourself will more than likely not be worth the time and trouble in my humble opinion. <br /><br />You should be able to find one ready made or like previously stated, install a quality sea strainer.

 

[rodbolt]

Re: Hull mounted heat exchanger?

hello<br /> I think your refering to what we called a keel cooler. dont do it<br /> you wont like it<br /> there are many kits for less than 1000 dollars that are "full" cooling. meaning the only thing raw water passes through is the exhaust risers. you will be much happier with a kit. we found keel coolers dont work well on high speed v8's. used to be a lot of them about here when everything was 4 and 6 cyl car engines in old wood 30 ft shad boats.<br />direct drives and all <br />was a run what ya brung thing. dry stack exhasts and all.<br /> glad its all gone now<br /> good luck and keep posting