jet units (how much, buy, price) - Alaska (AK) - City-Data Forum

rotorhead · 11-18-2008, 12:33 AM

Hey you outdoor types, gotta a question for you all.

I've got a fifteenish foot welded aluminum skiff (pretty heavy duty), fairly flat bottomed and already has a tunnel for a jet unit. I bought it with a 25hp Merc outboard with a regular prop, but to get it in the river I'm looking at a bigger motor with a jet unit.

I'm thinking maybe something in the 50-75 hp range, preferably with a factory jet pump meaning probably a Yamaha or Evinrude. The older Yamaha 2-strokes with oil injection seem to have a pretty good rep locally, but they're impossible to find and pricey when you do. I've heard both good and bad about the Evinrudes, specifically the E-tecs. It's a lot of $$$ for a new one, probably more than I spent on the boat and the motor thats on it now so I'm looking for advice.

Anyone have experience with a rig like that, specifically the new four-stroke jets?

warptman · 11-18-2008, 12:42 AM

Is this boat a custom made boat? Or is it a boat you buy from a dealer? They normally have a HP rating on the back. If you want a outboard with the 50-70hp range, that means if it had a lower unit it would be about a 90hp motor. You lose somewhere around 15-25hp when you up a pump on it. My lund is rated for a 90hp prop and not sure on the jet pump. For now I have a 50hp Yamaha fourstroke. Have you checked craigslist? Might look in there. Dewey's Cook Inlet sells the Yamaha outboards and Alaska Mining and Diving sells the Evinrude.

Arcticthaw · 11-18-2008, 12:52 AM

A couple of things to keep in mind. One the tunnel needs to be low and tapered corners. No place to trap air and cause cavitation. Tunnels with vertical sides don't do well for shallow water.
One thing in general I learned about outboards and such is that weight will be the issue for length of boat etc and how much your hanging off the back side. this could be an issue for a 4 stroke. A 50 to 60 hp with a jet pump would make a nice skiff for shallow tight rivers and creeks. If the boat is factory there should be a coastguard plate showing max hp. Keep this in mind for jet hp as different pumps seem to be derated more the older model they are. I have enjoyed larger V4 Evenrudes from the 70s and late 80s. They are pretty bullet proof. Don't know much about the injected ones.

Rance · 11-18-2008, 12:55 AM

You could scrounge up a used or wrecked jetski/tigershark and install that motor and jet unit inboard! There are a few doing that and I hear they work real well for very shallow streams. As long as the boat isn't real heavy.

Marty Van Diest · 11-18-2008, 09:10 AM

If it's a heavy boat you better go on the higher end of that range. I had a 15 foot very light weight jon boat with a 40hp evenrude with a jet. That's about the minimum for that boat. It worked fine but we couldn't put much of a load in it. A passenger in the front and a driver and that's about it.

I'd say the 40 jet was about equal to your 25hp.

starlite9 · 11-18-2008, 11:34 AM

Quote:

Originally Posted by rotorhead

Hey you outdoor types, gotta a question for you all.

I've got a fifteenish foot welded aluminum skiff (pretty heavy duty), fairly flat bottomed and already has a tunnel for a jet unit. I bought it with a 25hp Merc outboard with a regular prop, but to get it in the river I'm looking at a bigger motor with a jet unit.

I'm thinking maybe something in the 50-75 hp range, preferably with a factory jet pump meaning probably a Yamaha or Evinrude. The older Yamaha 2-strokes with oil injection seem to have a pretty good rep locally, but they're impossible to find and pricey when you do. I've heard both good and bad about the Evinrudes, specifically the E-tecs. It's a lot of $$$ for a new one, probably more than I spent on the boat and the motor thats on it now so I'm looking for advice.

Anyone have experience with a rig like that, specifically the new four-stroke jets?

If the boat was commercially built, the max hp rating for it is posted on the inside transom (back end) and it will also have the load/passenger limits as per Coast Guard Regulations.

The Hull Identification number should be on the outboard part of the hull on the Starboard Stern side (right side if you are standing behind the boat facing it). The last two numbers will tell you the manufacture date, they are the boat version of the VIN numbers for a car.

If you use a jet unit, it will lose about thirty percent of the rated horsepower. So you can figure upping the HP for a outboard jet to match that of a prop unit.

The four stroke engines now manufactured are very good, and they get about three times the fuel economy of what the two stokes do. But they cost a bit more new, used ones are a bit scarce where the older two strokes are all over the place...

The foot of the jet (Leading edge of the intake) needs to be set at the same level as the bottom of the hull so that it will not cavitate if not far enough down, or will cause a drag if too far into the waterflow below the hull line.

If you post a picture of the Stern, it may be a bit more helpful.

warptman · 11-18-2008, 12:34 PM

I don't know about anyone else, but I don't want a picture of Rotor's rear end!

starlite9 · 11-18-2008, 12:55 PM

Quote:

Originally Posted by warptman

I don't know about anyone else, but I don't want a picture of Rotor's rear end!

Ummm, never thought about that....

Never mind.....

rotorhead · 11-19-2008, 01:39 AM

Hey, they don't call him "warpt" for nothin you know...

In any case, the pics will of course be of the boat's stern end, still far more attractive despite the crusty dried seaweed and scunge from a summer in the water down at the small boat harbor. Ummm, yep, gotta get the power washer on it one of these days.

It's just a bit less than fifteen feet long, but without the snubbed bow it'd probably be a seventeen footer. It's pretty heavy duty, all welded aluminum with a double bottom and about eight-ten inches of floatation space between. The belly skin is maybe 3/16s thick, the rest is thinner, I suspect it's at least a couple hundred pounds even without the motor.

There's a stamped-in sorta-VIN (a few digits short, though) and it's title says it was made by "Daves welding shop", I think in either Sitka or Petersberg, somewhere in SE anyway. No HP figures but the transom is very heavy duty, it's twenty inchs from the top of the transom to the top of the tunnel cutout. Speaking of which,

The tunnel is maybe eighteen or twenty inches long, tapered sides, a bit less than two inches deep at the stern. It's obviously made for a jet unit, but which one...inquiring minds want to know.

warptman · 11-19-2008, 01:46 AM

Oh this would be easy. Get a outboard with a 90hp powerhead, this will give you around 65hp at the pump. It would suit this boat no problem. The tunnel is perfect for it! It looks like they got the design from a Wooldridge boat. Which model outboard would be up to you. NAPA has aluminum cleaner, you spray it on and hose it off, get some of this for the bottom and sides. Make sure you get a mask and use rubber gloves and eye protection when you do this. It'll look brand new. Goodluck!