Yamaha 784cc into welded mod-v hull

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Jim
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Yamaha 784cc into welded mod-v hull

Post by Jim »

I am in awe man. :beer:
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86tuning
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Yamaha 784cc into welded mod-v hull

Post by 86tuning »

Jim wrote:
03 May 2020, 10:18
I am in awe man. :beer:
Haha thanks Jim! I'm grateful for the opportunity to blog my build here on TinBoats.net. It's taking forever...maybe I'll finally get it wet this summer. There are so many people and resources here that have helped me get started. Would have been a lot harder to take the leap if it wasn't for TinBoats.net

Cheers,

Brian

86tuning
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Yamaha 784cc into welded mod-v hull

Post by 86tuning »

Well I tried several local machine shops and gear cutting shops, nobody wants to tackle this thing. They're all referring me to each other's shop. One gear shop tested the hardness and determined that their HSS cutters won't cut the material. The other shop said they didn't have a cutter for the JIS splines, but even if they did, estimates that this is likely a $1000 job. Which is a complete deal breaker.

So I'm sending the shaft across the country to minijet.INC to have them modify and send it back. They want the coupler shaft as well to confirm fitment, which makes it more fun to package up. Either I send two packages, or make some big package to ship the coupler with the shaft.

Instead of sending the whole coupler, I decided to disassemble the coupler shaft and simply send the splined portion. So I need a coupler wrench, which isn't hard to obtain, but I don't want to wait for shipping and customs to get from the USA.
the headache that nobody wants to touch
the headache that nobody wants to touch
DIY coupler wrench. I made it out of 1/4" aluminum instead of steel so it's softer, but needed a strong drive section. So I used a lugnut, and welded it to a backing plate. Then put some random beads in the aluminum to prevent rotation. I don't recommend this, instead simply buy one from Greenhulk or any of the other jet ski suppliers. Or better yet, have a jet ski shop r&r the coupler for you.
making a coupler wrench, part1
making a coupler wrench, part1
part2
part2
part3
part3
Now I don't have a holder, but since the shaft will be shortened, I can use the existing splines to hold the coupler. To keep it from turning, I welded a bump on the shaft. The couplers are on quite tight, and are retained with Loctite 572 pipe sealant.
anti-rotation bump
anti-rotation bump
Thankfully I have a good impact wrench, and it made removing the coupler simple once I had made the special tool.
separation anxiety
separation anxiety
tool6.jpg
So now with the shafts in a more manageable size, I can slide it into a piece of plastic pipe and mail it.
before
before
coupler at left, shaft on right. slid together to reduce chance of shipping damage.
coupler at left, shaft on right. slid together to reduce chance of shipping damage.
packaged securely!
packaged securely!
And it's off via parcel post. Not sure what shipping is going to cost, but at least it's on it's way. Might even see it back before the end of the month. I've asked they return the cut off section to me, so that I can use it to reassemble the coupler, and not have to buy any more special tools.

Cheers,

Brian
Last edited by 86tuning on 05 May 2020, 21:03, edited 1 time in total.

CedarRiverScooter
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Yamaha 784cc into welded mod-v hull

Post by CedarRiverScooter »

Quite ingenious! I make my own pullers too, sometimes they even work :wink:

Glad you found a shop to rework the driveshaft.

I suspect the carrier bearing on my jetjon is bad (VX110 engine). I think it is same coupler. So don't junk your tool just yet, there may be a buyer for it.

Something in the drive train is binding up & I suspect that bearing. Unfortunately, I have to lift the engine just to check it.

86tuning
Posts: 87
Joined: 11 Oct 2017, 01:49
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Location: BC Canada

Yamaha 784cc into welded mod-v hull

Post by 86tuning »

CedarRiverScooter wrote:
05 May 2020, 20:14
I suspect the carrier bearing on my jetjon is bad (VX110 engine). I think it is same coupler.
Shouldn't need to unscrew the coupler from the shaft to change the bearings. They're press fit, and you should be able to have the bearings replaced without pulling the coupler off the shaft. Getting it apart is another story, if the pump and shaft are slid off the back, maybe the coupler assembly can come out? Not sure, I'm not a jetski tech and have zero experience.

If you need a coupler wrench, I recommend buying one. It's about us$28 from quite a few sources. You'll also need a spline tool to hold the coupler shaft, which will be available from the same sources. I just didn't want to wait, and had materials here to make one. Shipping times are quite uncertain these days.

Cheers,

Brian

86tuning
Posts: 87
Joined: 11 Oct 2017, 01:49
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Location: BC Canada

Yamaha 784cc into welded mod-v hull

Post by 86tuning »

My materials have arrived from the bending shop. Almost have everything I need, other than the impeller shaft, which is still in transit to the machine shop according to the post office. It's been one month now, and their delivery date is to be determined which I hope isn't a euphemism for "lost."
some custom formed 2mm and 3mm aluminum
some custom formed 2mm and 3mm aluminum
The walk-around gunwales I had in mind will do three things:
1. allow walking around on the gunwales (duh)
2. increase structural integrity of the hull with the large box section
3. add some flotation to the hull, as they'll be sealed and pressure tested

I hope it works out the way I envisioned. Temporary mock up to check fitment.
port side gunnel cross section
port side gunnel cross section
The other pieces are floor stringers to support the cockpit sole. It's actually high enough to almost self bail, so I may install a plug on the side of the hull, and/or scupper valves. But that will wait until after the water test.

The stringers are again temporarily mocked up to check fitment. They'll be installed amidships and not at the transom as pictured. The engine bay and motor mounts are completely different design.
view looking forward, port side
view looking forward, port side
view looking aft
view looking aft
The cabin sole will be plug/rosette welded in place, and will be a sealed and pressure tested chamber as well, to offer flotation. Technically, it's not recommended for a hull member to serve as flotation, but if I puncture 1/8" aluminum I have bigger problems to deal with. With just longitudinal floor stringers, if there is impact on the hull it might dent but shouldn't tear. The box shape will impart significant strength and stiffness to the hull as well. Or at least I hope.

Over the next little while I will build the cabin sole and the conduit for the controls and electrics. I hope I don't warp the crap out of the hull, there is very little distortion at this time.

The saga continues....

- B

CedarRiverScooter
Posts: 1109
Joined: 13 Nov 2014, 08:01
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Yamaha 784cc into welded mod-v hull

Post by CedarRiverScooter »

Wow, that is going to be 1 stiff boat.

Maybe you could seal the bottom compartments individually, so a hole in 1 won't mater as much.

BTW, if you rip a hole in hull, it is because you are in shallow water. My wife & I both think we need to have helmets more that life jackets :wink:

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