Jet Drive Dinghy Propulsion

[category4jay]

After talking to an experienced sailor in Honduras who ran over himself with a prop driven dinghy (very bad outcome) I researched jet driven dinghy's. These guys seem to offer a good product. Yes the drawback to jets are clogged impellers but after talking tothis guy.... Any feedback from anyone else?

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[witzgall]

Jet drives are also not nearly as fuel efficient as a traditional drive, all other things the same. I am not sure of the difference - maybe 30% or more? I checked out the link you posted. They look very slick, but wow, the smallest model weighs 270kg/595 lbs!!!

Chris

[capn_billl]

Jet drive attachments to outboards are not a good working solution. Use a tether connected to an engine stop,

One thing i've often wondered is why not an enclosed prop? A ring around the prop blades can be designed to actually improve efficiency at low speeds. Less chance of wrapping lines, and rub burns instead of amputations. Also manatee safe.

Slightly more drag at high speeds, requires more torque from engine to spin up. smaller chance of damaged bent broken props when you run aground. (harder to repair if you do break it.

I've often been tempted to fabricate one myself to test it.

[Dustymc]

Originally Posted by capn_billl

Jet drive attachments to outboards are not a good working solution.

They're actually a great solution to a fairly specific set of problems. I agreed earlier that I don't think this is one of those problems, but blanket statements are false.

Originally Posted by capn_billl

Use a tether connected to an engine stop,

??

Originally Posted by capn_billl

One thing i've often wondered is why not an enclosed prop? A ring around the prop blades can be designed to actually improve efficiency at low speeds. Less chance of wrapping lines, and rub burns instead of amputations. Also manatee safe.

Slightly more drag at high speeds, requires more torque from engine to spin up. smaller chance of damaged bent broken props when you run aground. (harder to repair if you do break it.

I've often been tempted to fabricate one myself to test it.

The OP's (2-year old) question was about banging up the motor. Having spent a fair bit of time running around in shallow water, I'm absolutely certain that beefing up the things that break on outboards will just lead to the next-most-fragile thing breaking. Drive legs and transoms are expensive.

I'd also bet that OP's kid got tired of changing shear pins roughly two years ago and subsequently got pretty good at not running into things....

Premier Marine, Inc. looks interesting. It was apparently developed to be diver-safe, and shouldn't have at least some of the issues common to "normal" outboard jet drives.

[NCountry]

Man, talk about timing. One of my clients has a brother that is a really good mechanic. The other day we were both filling up at the same set of pumps and I was looking at the fishing boat they were pulling. This guys brother had taken a jet ski motor, cut out a portion of their flat bottom (metal) fishing boat and installed the motor and drive from a jet ski. The brother told me it took him a little time to fix a few bugs but that the thing worked GREAT! He could make it into backwater and up creeks that were completely off limits to everything else on the water. Due to the weight of the motor in the bottom of the boat it ended up being incredibly stable and his fuel consumption was less that when the motor was in his jet ski. It was also light enough, boat and all, that the 2 of them could lift it off the trailer and launch it anywhere... now I'm wondering if it would be possible to fit something like that in my hard dink.... dang, that would be awesome....

[capn_billl]

Sorry didn't see page one. I was replying to catagory4jays post about a guy running overhimself with a dinghy prop. The jet drives I've seen for outboards are a rotary fan enclosed with a center feed duct on the bottom. Big loss on speed, control and easy to clog feed duct. The durajet looks good, that is what I was thinking of.

[Dustymc]

Originally Posted by NCountry

Man, talk about timing...[cool boat...etc].......I'm wondering if it would be possible to fit something like that in my hard dink.... dang, that would be awesome....

Jets suck up junk, and sometimes you have to dig that out and fix whatever it's chewed up in the process of getting sucked in. That can be impossible on inboard jets, even if they have a stomp-grate. Even with all their problems, nothing that floats beats an outboard jet for really shallow work.

Originally Posted by capn_billl

Big loss on speed

Depends on the boat, but mostly.

Originally Posted by capn_billl

control

I know what you're saying, and as far as the boat goes I suppose it's true. Once you learn to use that "lack of control" to your advantage you'll feel like every prop outboard you ever run afterwards is a lethargic non-maneuverable accident waiting to happen. (25 feet of keel on 20,000 pounds of sailboat now helps me keep it all in perspective, but still!)

Originally Posted by capn_billl

easy to clog feed duct

Oh yea.