Setting up through hull cooling
The conventional method of cooling an engine in a marine environment is to have a seacock where salt water can be drawn in and used to cool an internal water circuit connected to the engine. These units require diligent maintenance, especially with sacraficial anodes, or they will corrode very quickly.
There is another alternative with steel boats that makes more sense to us, through hull, or skin cooling.
There isn't a whole lot of information or research available on this subject, just examples of other peoples experiences.
There are two methods of closed loop skin cooling:

1-A split pipe along the outside of the hull, around the keel
2-A "box" inside, atteched to the hull

Heat dissipation calculations could vary widely depending on the dimensions of the box, square, rectangle, number of baffles etc.
With a split pipe the same thing has occured, and small baffles really need to be used....but then again, maybe not!

We have decided to go with the box type as this won't effect the outer hull. Origionally it was going to be a square, about 15 square feet, on each side. But because of conflicting data we have found, ( ie 1/2 square foot per horsepower to half that again, to almost twice that! ) we are making it length-wise. 16 feet long x 1 foot on each side.

For this we have had some 1/8" plate cut into 11" to 13" strips, and bent to a 45 on the sides. Of course this couldn't be used whole ( it would've been nice! ) as it needs to curve around the hull between stringers. ( Photo at the top )
We are going to place baffles every foot or so to keep the water stirred up. This is very important because the flow isn't very fast and without baffles, the hot water would just remain at the highest point, away from the hull where the cooler water is!

I cut out 1 1/2" high slots through 8 frames and then slightly bent each piece so it would slide in easier ( by jumping on it haha !) then marked and cut the ends to get a "curve" in the overall shape.

The reason we went with 45 on the edges was so Gena could easily get good welds to the hull along side the stringers.
Tomorrow we will put in the baffles. This will take some time as the origional idea was to accomplish 1" inside depth for 1" flatbar baffles. Unfortunately there must have been a misunderstanding on where the 1" dimension was to be because the depth is only 3/4" ! This means lots of grinding.

Day 132:
7 hours - Cut and fit thru-hull cooling plate, cut 16 slots into frames.

To DAY 131
Now available at


To DAY 133