View Full Version : Jag motors in boats

03-12-2002, 12:10 AM
I am building a 25' wooden boat, similar to a Hacker, and want to have the thrill/sound/excitement of the V-12's of the 30's and 40's. Has anyone done a marine adaptation of the Jag V-12? For a very short while, Jag did build/adapt engines for boats, but this was dropped during the Leyland period. Any advice, ideas, hate mail is welcome. This would be either a closed or open system, with diligent attention to saltwater intrusion. Thanks. Rob G

03-12-2002, 12:38 AM
Sounds like a neat project. The easiest cooling system would be a keel cooler (maybe two) mounted way aft and just use the engine’s water pump. Not sure if you can get by with a dry exhaust, it would have to be well insulated and the doghouse well ventilated. The most popular reverse gear is the Borg-Warner Velvet Drive, and they are often set up for an SAE #3 bellhousing….should be easy to adapt to the Jag engine with the standard auto trans “flexplate”. graemlins/thumbsup.gif

66 fhc
03-12-2002, 01:46 AM
It does sound like a great project. How far along is it? I'd love to see your progress in photos. Could you work with Basil on that? Where did you learn to build boats? graemlins/hammer.gif

03-18-2002, 12:01 AM
Thanks for the input. The boat is basically a cold-molded model, from Ken Hankinson in Idaho. I tried building one from old Hacker plans, but way past my skills. Having lived on the San Diego Bay for several years, I realized that fast boats would go well, and the various LA companies that put Chevy engines in XJ types meant a lot of 12 cylinder engines dripping oil onto vacant lots. Having been told the Jag engine is only good for an anchor (from a Corvette freak), I think it appropriate to respond with fast wood and (hopefully) elegant lines. Will keep you posted with my progress, as well as recovery. Don't try and fiberglass upside down on the hull and realize that your hair has adheared to the hull. Maybe if I chrome the hair, the boat will go faster.

03-18-2002, 12:08 AM
PS to John: thanks for the input. I thought about keel coolers, but I wonder if the speed of the boat would be negated by the cooler, although I have seen rather sleek ones. I run my Chris-Craft in San Francisco Bay with open cooling, but I also have to flush the engine completely. The closed system would be a bit heavier, and need a surge tank. As for the exhaust, I thought that straight dry stacks to each side would suffice, as long as I could cool the doghouse sufficiently, but that would put the exhaust and noise in front of the control cockpit. I think Jag once made watercooled manifolds, and it would involve some fancy plumbing, but I think it would be worth it. I would like three carbs, but that would also mean three flame arresters. Thanks for the input on the bell housing: so many ideas, so much need to win the lottery. Rob G

03-18-2002, 01:39 PM
Hi Rob

I still like the keel cooler concept, no aux water pump, heat exchanger (with res tank) etc to plumb and hang on the motor, and not much of a weight penalty (maybe and extra 3 gal of coolant). The one I’m thinking of is the style used on the old Navy 26’ wood whaleboats……about 10x15”, bronze with just an inlet & outlet 1” pipe as I recall, and are pretty much “flush mounted” with the fins recessed even to the hull. They are designed to handle the BTU output of the old Buda DA/DD diesel (250 cid?) so I’m pretty sure that two in series near the centerline and way aft close to the transom would do the job without adding too much drag/resistance.

The dry stacks out the side would let everyone know you are coming, for sure.

Keep us posted……….