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.
shaft2.jpg
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.
tool1.jpg
tool2.jpg
tool4.jpg
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.
tool3.jpg
Thankfully I have a good impact wrench, and it made removing the coupler simple once I had made the special tool.
tool5.jpg
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.
pack3.jpg
pack1.jpg
pack2.jpg
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
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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
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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
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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."
materials.jpg
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.
gunnel.jpg
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.
ribs1.jpg
ribs3.jpg
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
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CedarRiverScooter
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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:

86tuning
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Yamaha 784cc into welded mod-v hull

Post by 86tuning »

Cedar, I never really thought of it that way. Would take a high speed impact on something immobile to pierce the hull, since the projected weight of the boat is well under 500kg. And that would only happen in shallow water. I feel a LOT better now. Because flotation would really only be important in deep water, which I will venture to when I troll for salmon.

Progress update: I managed to figure out the assembly order for the boat. I can't do anything further with the driveline until the impeller shaft is back from the machine shop. So now, onto the hull. It's finally GO time!

Preparing rosette welds. Had to do some more math, because I wanted somewhat close hole spacing, and at the same time, an odd number of holes that I could 'middle' each time I welded. So that would mean 1, 3, 5, 9, 17, or 33 holes. This way I can weld the middle in place, and weld each end, then in the middle of each weld, over and over again to reduce pulling and warping.
ribs7.jpg


the stiffener brace is 82" long, so I decided on 5" spacing, for two rows of 17 holes. Then I drilled them at 1/8" pilots, and then 1/2" final dimension. I happened to have a larger drill bit available to debur and chamfer the holes quickly and efficiently. I've always wanted a countersink bit, but have been too cheap to get one my whole life. lol.
ribs6.jpg
I inspected the inside of the main hull seam for deficiencies. I had done this a year ago, and it definitely warranted inspection. I ground out any craters and signs of porosity, and then re-welded any low spots. A close fit for the hull stiffener is required. Then I started tacking it. First the middle, then the aft end, and now I have a small headache to deal with at the forward end.
ribs8.jpg
The hull begins to curve at the very end of the stiffener, but there's a gap behind it. Might have to drill thru the stiffener and bolt it together. welding a dog to clamp it down seems to be more work than a thru hole. In any case I have to grind out one of the welds at this spot today. Might have to use the lifeline and beg my buddy to come help lol.

In other news, the post office has notified me that my impeller shaft has finally arrived in Ontario after a 5-week journey including the 3-week delay. Now to wait on the machine shop, and choose an alternate shipping method for them to send it back. Yay progress!

Cheers,

- B
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Last edited by 86tuning on 11 Jun 2020, 02:40, edited 1 time in total.

CedarRiverScooter
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Yamaha 784cc into welded mod-v hull

Post by CedarRiverScooter »

I would just 'slug' that gap with some scrap material & weld it in place.

Keep in mind you only have yourself to please.

86tuning
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Yamaha 784cc into welded mod-v hull

Post by 86tuning »

Buddy suggested trying self-tapping screws before thru bolting. So I drilled a 3/16" hole thru the top layer, and a smaller hole thru the bottom layer and put in some screws. Seems to have done the trick. You can see the weld that I ground out in the lower right corner of the pic. It's now sitting flush. When I fix the through-holes, I'll be cutting the top layer to rosette weld at the same time.
ribs8b.jpg
With the rosette welds all in place, I started with the stitches on the side of the keel doubler. And then began to add the longitudinal braces. The height and width of these are designed to put a small camber curve into the cockpit sole so that water won't puddle, but rather flow to the sides like street gutters. Of course this depends on boat's list, but I'd rather avoid puddling if I can in the design phase. The idea is that a curved floor will be slightly stronger as well. I'm using .080" for the floor, which is heavier than needed, considering that most tin boat hulls are 1/16" or .062-.064" and with 8" spacing between the floor supports it is a bit overkill at this point.
ribs9.jpg
Also have to deal with some other smaller warpages, and supporting from the bottom is helping. This is the part of the build that's somewhat nerve wracking, trying to keep the hull from warping as I weld. I made an adjustable support to help deal with that. It's working so far, but I have nightmares of putting a twist into the hull. Tying it down to the cart is helping a bit too.
ribs8c.jpg
ribs8d.jpg
The bow and stern eyes I ordered have arrived. They're cast aluminum, so they'll be a bit tricky to weld up. Might have to switch to 4043 which is supposedly better for cast aluminum.

Also the 135 deg helm unit is here, along with a super-budget 13" steering wheel. I figured I didn't want the 60 deg unit that came with the ski, and 135 would allow me to keep my finger on the throttle. 270 might be easier to steer and less twitchy, but probably not ideal for finger-throttle application. I'll be using 33C or 43C style control cables, like what was on the ski, instead of a steering cable$$ because it's a light weight low power application compared to the 400+hp full size jet boat. I haven't worked out all the cockpit details at this point, but may try a bike brake lever, or else an aftermarket finger throttle. Or might just wrangle something together. But that's a tomorrow problem.
eys1.jpg
parts2.jpg
Cheers, - B
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86tuning
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Yamaha 784cc into welded mod-v hull

Post by 86tuning »

Well today I managed to improve the setup of the welder. Quick recap, I'm using a Lincoln Weldpak 180HD which is the same 220v unit you'd find at Home Depot and others. It has stepped voltage settings instead of the continuous settings of the premium weldpak 180. I'm using a generic blue ptfe liner, and pushing 5356 wire from the unit itself instead of a spool gun.

I managed to find some .035" wire and some .045" contact tips. I also refreshed the gun with a new diffuser and nozzle. Not Lincoln brand, but generic tweco-compatible consumable bits from a random online supplier. Next I carefully straightened the neck portion of the gun a bit. It was clearly past the 45deg angle, and with it closer to 40deg I figure it would feed more smoothly. I brushed clean the feed rollers, and completely loosened the drive roll setting and the spool holder tension. After dialing in the wire speed and voltage settings, the sporatic feed problems I was having with the .030" wire are completely gone. I haven't had a single birdsnest for this entire pound of wire. Now that I've said that, I probably have jinxed myself. The roller feed tension is as light as possible, and the wire will slip in the drive rolls if the wire burns back and sticks in the contact tip. Argon flow is increased from 19cfh to 25cfh.

Also, at the suggestion from my mentor, I've tried getting some gas pre-flow to shield the arc before it strikes. The machine isn't set up for it, but with the wire trimmed right back to the tip, and then blipping the trigger once before holding it I can get a burp of gas to the weld site. This, along with the slightly increased flow setting has greatly improved the consistancy of my welds without a spool gun.

So why not just get a spool gun? It's because I want greater access to tight areas and corners. And it's bulky. And the additional cost of course. And I'm stubborn and want to do it the hard way sometimes. But now it works fine! I went down this whole path because my mentor, who has since moved away, used to do tons of aluminum welding with a similar setup. They just pushed wire through the whip. So if you're trying to weld without a spool gun, don't give up! It's possible, but the learning curve is somewhat steep and frustrating.

Cheers, B

CedarRiverScooter
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Yamaha 784cc into welded mod-v hull

Post by CedarRiverScooter »

Great story on getting it to feed alum wire.

I used my antique miller to weld alum through the cable & more wire went in the trash than into a weld. But I was too stubborn to buy a better welder. There is no spool gun available for a 50 yo millermatic.

Keep up the good work & the pictures.

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

Yamaha 784cc into welded mod-v hull

Post by 86tuning »

Well the shaft finally arrived in Ontario after 5 week hiatus. Apparently the Post Office in Missisauga was shut down several times. But it was delivered. Three weeks later the machine shop had cut and resplined my shaft, and sent back both pieces via courier, and they arrived in 3 days. Yay!
shaft.jpg
I am well pleased with the work, and the price, and the speed of return shipping. Quick shout out to MINIJET.inc for speedy service with great communication at an excellent price.

Now with the shaft back, I get to re-assemble the coupler and the jet pump. Half way through, I'm looking at the parts, and I don't know where the two black washers fit. The big one is a spacer, but the little one? No clue. The repair manual has no photos, so I simply pressed the bearings and shaft back together into the stator housing. I put the spacer in, and decided the small rubber washer must fit in behind the impeller.
leftoverparts.jpg
pump.jpg
After dinner, I decided to use the power of the internet to figure out where everything fits. And I found this excellent writeup with photos of where all the pieces go.

http://greenhulk.net/forums/showthread.php?t=150826

After reading that, I find that the rubber washer doesn't belong. Not sure where it goes, but it defintely needs to be removed. So I'll take the impeller back off tomorrow. If it's stuck, I'll have to take the pump to the boat shop to use their spline tool again.

Well, while I was figuring out the pump, I decided to remove the fuel tank from my front cut. So I siphoned out the gas into a jerrycan to pour into my truck's auxiliary fuel tank. This way it's safely stored, and can be mixed in with fresh gas at any ratio I choose. I drained about 12 gallons out of the tank, and the gas is about 2.5y old and smells like paint thinner. It was 94 octane ethanol free, but now smells more like 74 octane. I hope the truck doesn't run too rough when I blend in the old gas.
tank1.jpg
Years ago, when I first started working on this ski, I dropped an 8mm socket into the abyss when loosening one of the many hose clamps on the engine. After fishing around for half an hour, I decided I needed a pair of wrenches to deal with all the hose clamps. I've always liked Facom tools, so spent quite a few bucks on three of them. 1/4", 7mm, and 8mm sizes. These wrenches are one piece so the socket can't fall off, are compact so they reach clamps in tight spaces, and the other end gives tremendous leverage, way more than needed to loosen even the tightest hose clamp. Highly recommended. Money well spent. If additional leverage is needed, a small screwdriver or allen key can be slid through the short leg to get leverage and reach.
tank0.jpg
With the tank drained and removed, I could toss it into the nose of the boat to see if it fit under the proposed deck. Yay, will fit, and there's lots of clearance for reinforcement ribs on the nose of the hull as well. Only issue is that the filler neck is on the opposite side of the truck, so it will be inconvenient to fill both at the same time. Also, the filler neck hose isn't quite long enough to reach to the gunwale, so I'll need to figure out whether I want the original Yamaha filler cap or not. And since the cap is missing a chunk, I may elect to use a standard filler neck.
tank2.jpg
The cockpit sole has been prepared for plug welding to the longitudinals. 102 holes drilled, deburred on the bottom, and heavily chamfered on the top. Waiting for buddy to find time to come over and TIG all the watertight seams and spots.
floor1.jpg
floor2.jpg
See you on the water,

Brian
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