No limit to the jet squirt!

About using jet ski motors to power small boats

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Reynolty
Posts: 4
Joined: Mon Nov 06, 2017 11:30 am

No limit to the jet squirt!

Postby Reynolty » Mon Nov 06, 2017 12:02 pm

Gents-

I had my heart set on a jet squirt since I first saw the squirt design on Pinterest. I searched endlessly for the max size of motor the little devil could hold- largest I found was a 600 cc.

Being naturally frugal and an avid craigslister- I began searching for a cheap donor jet ski so I could save a lot of money on fuel tanks, wiring, steering cables, and on and on. The only one that really caught my eye was a 1000cc triple seater for 300 bucks.

I did some rough estimating on the engine weight, factored in a few extra inches for the engine length, then set out ripping that ski apart and taking everything out.

Long story short, 14 months and roughly 3500 dollars later, my 1000cc jet powered squirt was born. I was very hesitant about rolling it over or even about it sinking instantly due to the excess weight the moment I launched it.

That all said- I am extremely happy with the performance of this rocket on water. She tips out around 55-60, and I'm sure I will get more out of her once a rebuild the impeller (she was out of a 1991 and pretty well beat up).

I haven't tried pulling a skier yet, but am confident she would do just fine.

If anyone is considering a jet squirt build and wants to go with the powerhouse version- below is what I did to to beef up the boat-

-6 oz fiberglass inside AND outside of all plywood except the deck. (Only inside on the deck) Putting a layer of glass on the inside of the ply before flying it to the frame gives you tons more strength, as that glass layer resists any flexing pressure coming from the outside.

-Bronze silicon screws every 3-6 inches, on every joint. High stress joints I dipped them in epoxy before screwing.

-an addl layer of 15 oz cloth on the outside bottom portion to protect against extra engine weight (and secure the joint between fiberglass donor hill and wood boat hull)

-2 sheets of 3/4 Plywood epoxied together (5x32x1.5 inches) running from the transom to the first cross member, used those as engine mounts. Used aluminum angle iron to mount to the transom.

I know some pictures would be worth a thousand words, will try to get some up soon of the build process.

I have gone airborne in this thing a few times over some unexpected waves and so far she has taken the beatings we'll.

Good luck on the builds!

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BayouBengal
Posts: 926
Joined: Tue Jul 31, 2007 7:29 am
Location: Baton Rouge, Louisiana

Re: No limit to the jet squirt!

Postby BayouBengal » Mon Nov 06, 2017 1:34 pm

Congrats on the build and look forward to the pictures, or even better, videos.

By the way, "to each his own", but if I had a Squirt that would do 60, the only way I'd run her that fast would be via remote control from the dock. :D

DSR
Posts: 208
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: No limit to the jet squirt!

Postby DSR » Mon Nov 06, 2017 6:28 pm

Hi Reynolty,

Your Squirt sounds like a great build and I'd definitely like to see some pics or videos on how you built it and how it runs!

Since I decided to build my jet TNT, I've really gotten to like the PWC-powered mini jet boat concept and believe there should be many more of them. I think It's the perfect way to elevate personal watercraft into something that's actually cool and looks as good as it runs! The perfect way to dispose of PWCs one ski at a time...... :lol:

Congrats!! :D
Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

Reynolty
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Joined: Mon Nov 06, 2017 11:30 am

Re: No limit to the jet squirt!

Postby Reynolty » Sat Nov 11, 2017 6:43 am


JimmY
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Joined: Sat Jul 30, 2016 11:08 am
Location: Brighton, MI

Re: No limit to the jet squirt!

Postby JimmY » Sat Nov 11, 2017 7:41 am

:shock:
-Jim
Nothing says poor craftsmanship like wrinkles in your duct tape!

DSR
Posts: 208
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: No limit to the jet squirt!

Postby DSR » Sat Nov 11, 2017 8:48 am

Looks great Reynolty!
Judging by the last video, it looks like your Squirt handles the weight and horsepower really well. How much did you have to stretch the hull to make everything fit? It also looks like you don't have a lot of issues with porpoising either, so balance seems to be very good.

Nicely done!!

Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

Reynolty
Posts: 4
Joined: Mon Nov 06, 2017 11:30 am

Re: No limit to the jet squirt!

Postby Reynolty » Sat Nov 11, 2017 9:35 am

The video with my wife driving was at about 35 mph, no issues with porpoising until you hit 45-50, then it starts building. I've been looking at a small trim tab option but haven't had time to fabricate anything.

There is 12 inches extra length between the transom and 1st cross member, another 4 inches between the 1st and 2nd. I needed the extra 4 inches as I had to move the seat forward a little in order to clear the expansion chamber on the engine. I was a little worried about the 16 inch length change, especially with the additional weight.

I ended up mounting a 14 inch wide section of fiberglass off the jet ski hull that spanned the length of the engine on the bottom and up the transom to where the impeller mounts. This is where the majority of strength is coming from for the stresses acting on the back of the boat.
Attachments
20170430_142802.jpg
You can see the original jet ski portion of the transom

DSR
Posts: 208
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: No limit to the jet squirt!

Postby DSR » Sat Nov 11, 2017 12:17 pm

Not sure what ski you pirated the powertrain from, but do you have any options regarding installing adjustable nozzle trim on the pump? (unless the cable at top center of the pump is in fact a trim cable?)
You mentioned it being a '91 so I imagine not, but it would definitely be preferable to trim tabs. Trim tabs work but they do create additional water drag and will add some weight if you add any that are remotely adjustable, which would be better for your situation.
Something you might want to try before the trim tabs, and I don't spy one in your pic, would be to fab an adjustable ride plate extending from the rear of the pump intake back under the pump. I suspect it would definitely help with the boats atitude at higher speeds....

Thanks for sharing your Squirt Reynolty, it looks great and it obviously runs good!! (mebbe the fastest Squirt built?) :D

Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

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Roberta
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Location: East Troy, Wisconsin

Re: No limit to the jet squirt!

Postby Roberta » Sat Nov 11, 2017 1:43 pm

Pretty Cool!!! I also think the trimming of the nozzle is the best way, if doable. If you are maxed out on trim already (assuming you have that) just crank it out a bit more for the higher speeds. Lower speeds won't be bothered that much by a little extra bow down trim. But a small boat like the Squirt might be at its stability limits at 35 -40 mph.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

Reynolty
Posts: 4
Joined: Mon Nov 06, 2017 11:30 am

Re: No limit to the jet squirt!

Postby Reynolty » Sat Nov 11, 2017 4:53 pm

The original donor ski had a functioning electric trim for the nozzle but it has since gone kaput. I have it manually trimmed down all the way (even added an aluminum extender to the rod in the pic so i could hit the true mechanical limit of the nozzle). I'm not sure if I'm losing more power from the jet hitting the trim nozzle than I would lose from adding a trim tab and leveling off the jet.

Something to play with I guess. I like the idea of a trim plate right under the jet- I think that would look better than something hanging off the back and be much easier to install.

I haven't had a need for trimming the jet up, it seems to make porpoising occur at all speeds so I will probably pull the electric trim out so save a few pounds. Maybe retrofit a newer model in there if I get to feeling froggy.

I also thought about eliminating the lawn mower sized battery installed next to the transom and adding a 50 lb marine battery up under the bow with some long cables. It would add A LOT of weight, but I am in Savannah and the only place to run this thing is the intercoastal waterways, making a trolling motor "get home" capability almost worth the trouble.

Anyone seen a good method of using a small electric trolling motor that can be clipped onto a swim deck and stored nicely when not in use?

DSR
Posts: 208
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: No limit to the jet squirt!

Postby DSR » Sat Nov 18, 2017 8:11 am

Hi Reynolty,

From what I've learned, porpoising can be caused by several different things, and with the Squirt being both short and having a low-deadrise warped bottom design with very little "V" in the aft section of the hull, it's more susceptible to porpoising than other designs.

The first thing I would do would be to check the rear 4-5' of the bottom of the hull and verify that it's straight front to back with no hook or rocker. Even having 1/8" of either could cause problems. Also make sure that there is a pretty sharp corner at the bottom of the transom where the bottom planking ends. Having too much radius there can also cause problems.

Once those things are correct, then it usually becomes a matter of balancing center of gravity of the boat with the center of hydrodynamic lift as the boat goes across the water. To make it even more interesting, the center of lift "moves" forward and back at different speeds....

In your situation with your Squirt, if the hull is straight with a good trailing edge, the COG is behind the COL, causing the porpoising, as COG and COL try to meet each other, but can't quite get there.
I'm putting a heavy full-size marine battery up to the third frame (first frame aft of the bow on my TNT) way up under the deck, for better COG, and I would do the same in your Squirt.
The ride plate under the pump from the transom doesn't really perform as a trim tab would (even though a lot of people try to use it as a trim tab). The ride plate acts as an extension of the planing surface of the hull bottom and makes it act like the planing surface is longer than it is, to move the COL back closer to the COG and better balance between the two. A lot of times, the ride plate actually works better with a slight up angle from the bottom of the hull, as stupid as that sounds....

With the bottom correct, and there's a better balance between weight and lift, then you should be able to use the nozzle trim for what it's meant for, to fine tune the attitude of the hull at different speeds. Getting this stuff as close to right as you can will also let the boat work more efficiently, so speeds go up along with better control. :D

Sorry if I rambled on a bit there, it's a subject that I spent a lot of time on while I designed all the mods for my TNT, and I think it's a very interesting topic that a lot of builders have issues with on the faster boats.

As far as a trolling motor for emergency use is concerned, I think it's a great idea, and another reason for that uber-heavy marine battery. I would think that a tiller-style trolling motor with an "L" bracket that temporarily attaches to the swim deck would be very doable and fabbing a couple brackets to stow it much like the oar you have in your Squirt would work really well. Maybe even stow it in the engine compartment so it's out of sight until it's needed?

Thanks, :D
Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753


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