If air cooling didn't work out, you could remove the radiator and
instead pump the coolant through a coil of copper pipe running through
a sea chest (small seawater-flooded compartment built inside on the
inside surface of the hull). Kind of like a keel cooler, but inside.
The advantage over cooling with raw seawater is that you don't get
corrosion inside your engine, both from the seawater and from the
galvanic action it creates between the dissimilar metals in the engine.
Of course, it's slightly more complicated.

I'm not sure that I understand the continuous duty problem. Certainly,
truck engines aren't meant to run at 100% of rated RPM all the time.
However, they can do long 'passages' at highway loads, which (I think)
is around a third of rated HP. Truckers even leave their engines
turning at high idle while they're stopped. Why wouldn't you use a
400hp truck engine as a 100hp boat engine? If yours is a big ol' boat
running at displacement speeds, the difference in weight wouldn't
matter much. Anyway, I got the impression that when manufacturers sold
an engine as "continuous-rated" versus "intermittent-rated", half the
difference was simply reducing the rated HP. I could easily be wrong.

I've never done this sort of thing. I'm just thinking about how I'd do
it if I were in a 'gypsy' frame of mind, and I wanted a decent boat for
minimum cost. What do you experienced folk think?

-Max Camirand

Steve Morrisby wrote:
Ah yes!. I did not consider that the marine engine is continuous duty. Considering that fact the cost is probably justified.

Referring to Max Camirands posting, I also wondered about air cooling. Deutz built a fine range of air cooled engines, and it would keep the boat nice and warm!. But I am still up against the continuous duty problem.


Thanks for all your input.

Steve