Designing my ultimate river sled

[Impracticallaty101]

Howdy all,

Over the years, I've been taking in ideas of what all I want and need in a boat, and I'm looking for some input on some of my concepts that to most are completely unpractical, but that is what I like, cool factor, one off stuff that nobody else has and turns heads.

I'm up in Montana, and primarily run on the Yellowstone River, but venture to the Missouri occasionally and Fort Peck reservoir from time to time, the rivers are very rocky with minimal vegetation and more sand bars than mud bottoms for a little reference.

When I first learned of outboard jet boats years ago, I fell in love with the Wooldridge Alaskan design. Rugged, boxy, utilitarian looking with the 2 piece walk through windshield, but like most, my imagination exceeds my banking account.

For me it will never be feasible to request a manufacturer for a custom build, so I am wanting to build my own.

I am well versed in fabrication, and have access for the space required to take on such a venture.

So here's basic concepts/ideas list:
19-22ft in length
60-72in beam
Wooldridge Alaskan basic look

Now things are gonna get weird, I'm wanting to run twin outboard jet drives, either 115/80s, or 150/105s. I have a hook up where I could get a smoking deal on used outboards. On top of the ridiculous redundant twins, Im wanting to mount them on a (bare with me on terminology here) hunt deck, or extended hull, basically an offshore bracket looking setup that I see aluminum boats down south run, pictures included for reference.

Twin jet tunnels would be required, but I would like to keep the motors as close together as possible, thats where my inquiry on actual jet performance comes in. Ive only ever seen a couple outfits run twin outboard jets but the motors are spaced out fairly decent.

I would need this boat to be able to run super skinny water, so what I have in mind comparable to the Alaskan is moving the windshield forward closer to the bow, having all the batteries in the bow, and either having a long fuel tank running the length of the keel under the floor to try to maintain balance with this setup or also closer to the front.

Interior design would be very basic, the only storage needed would be lockable rod lockers and a dry box for life jackets and other essentials. 2 pedestal mounted seats for the driver and passenger, and other mobile set ups if more passengers tag along. The distance from the windshield to the bow is undetermined, the only requirement is being able to mount a 36v self deploying bow mount trolling motor.

One more thing for yhe rear that would add weight woild be 2 power pole, or Talon anchors.

Anyhow, like I said, I understand the the impractical redundancy argument, this would be all for me and the cool factor, any input on being able to make this setup work to the best of its abilities or other information is appreciated, Thank you.

 

[montero]

2 outboards are heavy so wider and longer hull you is what you need. You should recalculate LOA & BOA to compensate extra weight at the stern . Bigger size mean less hassle with balancing hull by moving everythink forward and and the weight distribution will be more forgiving.
Make some mockup stand for engines to check how close they can be .
Not familiar with tunnels but I'm also bit scepitcal especially "normal " propeller tunnels .

 

[Barry]

"basically an offshore bracket looking setup that I see aluminum boats down south run, pictures included for reference.
Twin jet tunnels would be required, " your comments


If you are referring to an prop outboard prop bracket, these, twin tunnels and a prop bracket, features are at odd with each other as you require the shoe (intake) to have clean (green) water coming into the jet.
The prop outboard bracket would position the shoe back from the exist of the tunnel and risk air getting into the shoe, with larger waves etc.

Turning ( say to the right as an example) COULD also cause left engine intake to more than likely ventilate.

Your illustration in your first post shows "what you believe" as the "best" trim angle at zero. This is not the case. You should have some angle of attach in order to provide dynamic lift and mitigate plowing of the bow. Depending on the deadrise, the boat requires some keel up attitude. At 12 degrees, 6 degrees, at less than 12, at least 4. Certainly for minimizing drag.

In fact, having the bow "down" can cause an issue with the boat doing Victory Rolls, where the stern swapps ends in tight turns. A good illustration is on a Shotover Jet video, there are many
that you can find on Google. (New Zealand- the birthplace of jets)

at the .37 sec mark.
Of course you will note that they do a 360 degree VR. Swapping ends 180 degrees is very common.
(you will also note some of the video head on show the keel being wet quite forward. Ie nose down. This is to facilitate precision turns without slipping out which this river run requires.


"""So here's basic concepts/ideas list:
19-22ft in length
60-72in beam""" Your comments

A wider boat will plane in less depth of water. A 60 inch to 72 inch BEAM is narrow. This would only give you perhaps a 50 or 60 inch CHINE WIDTH. Attaching 1000 pounds of twin 150 hp
motors will make the stern squat on such a narrow chine width

Our 21's had an 96 inch BEAM but an 84 inch Chine Width. Our inboard jet package with a 454 weighed about 1000 pound.

I think your narrow choice of beam with 1000 pounds mounted either off the transom or off some type of brackets with zero trim angle is not realistic.

 

[ondarvr]

Your smoking deal on outboards complicates every aspect of this and will cost you time and money, and probably poorer performance.

I live on a river and have run outboard jet boats for a very long time, and made semi custom ones. Plus my friends are guides and they've gone through many jet boats, including Wooldridge.

Due partly to the very inefficient design of an outboard jet they are extremely weight sensitive, even adding a small amount of weight can be noticeable. Adding it to the stern makes it even worse.

Tunnels are tricky to get right, Wooldridge does a good job with their design, but assuming dual tunnels would work in a similar way could be, and probably is, a huge mistake.

Save yourself many thousands of dollars and a couple of years of frustration and buy a Wooldridge if you like the design. Wooldridge boats tend to need lower HP to achieve good performance due to the flatish bottom and light weight, so a single one of your larger available motors is most likely all you'll need.

I'm a little sad discussing this right now, I just sold my favorite jet boat that I built 25 years ago. I didn't really want to sell it, but I didn't see where I was going to use it again, life changes and you need to adjust.