The Kneeslider

Doers Builders and Positive People

Harley Davidson Powered F-15 Mini Speed Boat

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Harley crate motor powered F-15 mini speed boat from St. Martin Mini Speed Boats
Harley crate motor powered F-15 mini speed boat from St. Martin Mini Speed Boats

Is it ever appropriate to ride your Harley in a t shirt and shorts? Sure, when you’re in your Harley Davidson powered mini speed boat from St. Martin Mini Speed Boats of Mentor, Ohio. Starting with their standard 15 footer, they mounted a Harley Evolution 1340 crate motor, added their own patent pending water cooling system, connected it to a Mercury Marine® Alpha stern drive and you have the boat you see here. Nice.

Harley crate motor powered F-15 mini speed boat looks good
Harley crate motor powered F-15 mini speed boat looks good

It’s not a big boat, obviously, 2 persons or 600 pound capacity, but it pushes all the right buttons. Painted in an orange and black color scheme and emitting the correct Harley sounds, you now have the perfect answer to those summer weekend dilemmas, ride the Harley or take out the boat? Why not do both?

Harley crate motor powered F-15 mini speed boat engine closeup
Harley crate motor powered F-15 mini speed boat engine closeup

There’s no detail on the site describing the water cooling though the photo here gives you an idea of what they’ve done. Is the engine rubber mounted to isolate vibrations from the hull? Also, no performance figures are available. Base price is $29,995.

Harley crate motor powered F-15 mini speed boat fans and cooling
Harley crate motor powered F-15 mini speed boat fans and cooling

We’ll be following up with more detail because I find this pretty interesting, but it shows what a resourceful company can do when someone asks, I wonder if you could …? Motorcycles, cars, airplanes and boats, is there anything the Harley V-twin can’t do?

We were pointed in this direction by one of our readers to the north who keeps up on the world of boats (retired Canadian Navy) and lots of other interesting mechanical technology. Thank you, Gerry!

Link: St. Martin Mini Speed Boats

Two videos below:

Comments

  1. I might be wrong but isnt liquid cooling the best choice for a watercraft ? Seems like the engine would run hot even with the fans..

    Do you have to wear a leather bathing suit to drive one?

  2. What do you get a person who already has everything else to go with the H-D tattoo across his forehead???

    …now I know.

    • No need for Harley jokes, this is a pretty cool installation. Regardless of what some think of the Harley V-twin, it’s a reliable and low maintenance engine and this application is an interesting idea. I don’t know how well it works here, the info available on the site is limited, but why not appreciate the engineering and work these guys did?

      • Ya sorry ’bout that, Paul. No harm meant.

        I live on a boat most of the year and I can only describe the battle with the corrosive environment combining galvanic metals, electricity (ac and dc), aquatic life, sun, weather and water (brackish, in my case) as…on-going. Hey, if these guys have a method of cooling that engine under typical marine stress – without dissolving it – then they have a technology that will generate serious interest. It is a very cool project, but I think an 850 Norton would sound better;)

        …now I have to go stuff the rear differential, pinion and axles back into my jeep.

  5. As a member of the Boating community I will tell you that $30K for something that will get noticed at the club is a steal!! Tie this to the back of your real boat for Bar runs and your good to go. Also this boat is made in Ohio so I doubt that it is intended for the corrosive world of Salt Water boating.

  6. i wonder if there’s any covert dialog between harley and these guys.

    after all, the kneeslider reported on hd’s own plans for a watercooling patent.

  7. Maybe its an oil cooling system? Cant see how they can liquid cool without special heads or barrels. Wonder how durable it will be since boat motors tend to be cranked wide open alot of the time

  8. I know liquid cooling is mentioned several time, but all I see is a standard HD engine with finned, air cooled heads and barrels and two small electric fans, mounted on each cylinder. It does seem to have a wet exhaust system, from all of the water (I hope) being blown out of the exhaust at the end of the clip

  12. You gotta admire ingenuity, but doesn’t it seem kind of ridiculous to use a poorly suited engine (air cooled in a boat) and convert it to liquid cooling (apparently, partially, maybe?) when there are whole bunch of other engines they could have used? Seems like a lot of work just to get the sound of the Harley twin. It almost suggests that the intended customers of this venture are regarded as more concerned with image than practicality or performance. Eh-hem.

    But, I admire ingenuity and this is pretty cool. I gotta admit that once this is all bolted together it’d be pretty cool to pull up to a dock in, even if it would get smoked by a john boat with a 75 Johnson.

  13. Many years ago I worked on a project to understand the differences in road going engine applications versus marine/aircraft applications of the same engine. Example: a standard 350cu in small block in a car/truck is ‘expected’ to perform nearly flawlessly and have near peak performance for 100,000 miles, but in an experimental aircraft they only rated to 50 hours between rebuilds (at that time). The difference is in the loading application. The same loading that is seen in aircraft is seen in marine applications, though the intensity is reduced marginally in marine.

    My point is: I wonder how long this engine will last in this application before destroying itself? I can only assume this is of little concern given the limited practicality of this boat.

    I like the idea though. Wonder how a ‘Busa motor would work? Maybe that V8 ‘Busa motor? Mmmm.

  14. Looks like a fine application for a big V-twin. Water-cooled heads will keep it mostly cool so the fans can handle the jugs, as long as the motor is in a stock state of tune and not run wide open for hours on end. How cool must it be to drive a boat with that big Milwaukee rumble? I only hope it is rubber-mounted to avoid shaking a hole in the hull and sinking to the bottom.

  16. Seems like a perfect application for the Motus V-4. It’s already liquid cooled, makes great noises and twice the power, plus it would probably survive that kind of usage better than the HD. I don’t think Harley would recommend running their big twin at max rpm and load all the time, which is what you’re going to be doing trying to race the kids with jetskis.

  17. Guys,
    It is NOT water cooled. I emailed the company and asked, when all I saw was cooling fins. They are taking water from the stern drive and cooling the engne oil through a heat exchanger. Nothing new for a boat engine. So, how hot does it get, I guess it depends on the duty cycle, but the engine was not designed to run without a lot of air impacting the fins. what the little fans will do it, very hard to say?
    Brian

  18. I couldn’t help but see the fans, and the corrugated hose ‘near’ them, and think, “Yeah, water cooled – pump some water in through hosing, out towards fans, then the water is sprayed over the engine” I’m a genius. And watch the engine dissolve, as someone above said

    **Of Course It’s Not That** – the oil heat exchanger Is the logical thing. But I ‘had ‘to think a bit perversely when I saw the pictures.

    Harley’s have their place. If they Ever made a real effort and made a better, 125 / 150lb lighte,r XR 1200 – whatever size, I’d have one in my garage – if it were reasonably priced.

    Now, once again, as someone mentioned previously, there’s Another niche (perhaps a hell of a lot bigger than ‘niche’) market for the Motus power plant.