Looking for your thoughts.....and a pump

I am converting a Zodiac 310 RIB to water jet power. The goal for this boat will be:
- Portageable <250 lbs. (no 1 part over 100 lbs.)
- Quick assembly/disassembly
- 18 to 25 mph in 4" of water.

Power will be 29 HP Kawasaki industrial engine. If my math is correct, a pump that uses ~160 HP at 6700 rpm should use around 25 hp at 3600 rpm. So, a PWC pump should work with little modification.

What I would like to find is a complete 155 MM pump with steering nozzle and reverse bucket in servicable condition. I will have to fabricate a new inlet and driveshaft, but having the old ones will help. I think Yamaha has the largest aftermarket impeller selection so I was thinking Yamaha, I could be wrong.

I have attached a rough concept model so you can see what I am trying to accomplish

 

I think you would be better off putting a PWC motor/drive/jet into a small aluminum jon boat. the drawing you attached doesn't accurately represent how big the components of a jet unit are, and if you are taking them apart from the hull for portaging you are going to have lots of leaks. As for portaging, how are you going to portage the plywood bottom if thats what it has? And if it doesn't have a rigid bottom, how are you going to mount the motor/drive/jet? As for those Kawasake (pun intended) "Industrial" engines...I would get something else, they are junk, just like their power tools and generators. I see PWC motors/drive/jets on Ebay all the time, get a Yamaha and use the Yamaha engine as well, then everything is ready to go. If you are going to run a jet in 4 inches of water, you better put screen on the inside of the intake grate or you will be sucking up rocks and those PWC impellers weren't made for that kind of abuse like outboard jets are, you will destroy them quick. What exactly are you doing btw? I do a lot of shallow water boating because I am a gold dredger in summer.

 

The reason for the inflatable is: it fits into the storage area of my 5th wheel. I put about 120 miles on one like it last summer and they have advantages.

As the pump and intake will be behind the transom, the only penetration will be the pump drive shaft and I will use a CV joint type of boot for that. The bottom is fiberglass. I check Ebay every couple of days, I'm sure something will show up. Sorry to hear about your experience with the Kaw. engines. I want to stay away from 2 cycles and all the 4 cycle pwc motors are too powerful and too heavy. I can’t find a outboard jet under 40 hp. This boat will come on plane with 2 people on a 10 hp outboard. I don’t have a need to go faster than that. I will look at some other engine options. I plan to fabricate an extra large water intake with a stainless grate with < 5/16” gaps between slats. The pump will be running at half the rpm’s it was designed for I am hoping it will not be so delicate.

I just like to explore lakes and rivers. When I was a kid my parents took me fishing a lot in western Ontario and my favorite part was going from lake to lake usually over a beaver dam or two. The bad part was dragging 16 foot aluminum boat through the woods. I will be retiring in a year and there is lots of exploring to be done.

I was up your way a few years ago, north of Manley Hot Springs. I was visiting a friend of my dad who was mining up there. How do you dredge in that water? I don’t think I could get used to it. It’s so cold it hurts. At least that’s the way it seem to us southern Ohio boys.

Thanks for the input,


Gary C.

 

The smallest outboard with a jet on it I've ever seen was a 30, you could probably find one, but they are heavy. I don't remember what brand this guy I know has, but he has a 30 jet. 5/16 gaps are too big if there is a possibility that you might suck up small gravel on a PWC jet unit. gravel that size will flat out ruin the impeller housing and the impeller. what I used was stainless steel aerator screen similar to the screen that is in most faucets with 1/16 or 1/8 inch openings at most. If you could find a Yamaha Superjet engine/jet/intake on ebay, I don't think they are too heavy since the whole ski only weighs a little over 300 pounds, but you can hook up any engine you want I guess. Kawasaki motorcycles are pretty good, but I don't put much stock in anything else they make, I had a Kawa generator once. Good luck.

 

Gary take a look at Mokai.com you my find that they have done the work for you at 150 lbs with 3 gallons of gas it is easy to get it to the water.

 

I seem to recall a Zodiac about five years ago that had something similar installed right from the factory... an 80-odd horse Yamaha engine sat under the console, and a little PWC-type pump was embedded in the keel below the seats. ProJet-350 I think it was called, and it apparently worked pretty well. The PWC's tiny axial-flow jet won't be nearly as efficient as a propeller though, expect to be somewhat slower than you would with an equivalent outboard.

 

Looked at the Mokai, it is nice. Someone invested some serious $ engineering and tooling for it. The biggest drawback is you can't take someone else along. I does fit my requirement of being portage able as separate components and easily reassembled.

 

I have a pump. It's out of a Yamaha xlt1200 with reverse. Just too long to mount the inlet behind the transom though. So I'll have to mount the inlet ahead of the transom. I hate loosing the space in the boat, but I can make the inlet longer and laser cut an oversized inlet screen. I'll take some pictures and post them as I go along.