Yamaha 784cc into welded mod-v hull

[86tuning]

Do yourself a favor as I'm sure you will use it plenty on future work, and just pony up the money for a decent 220v welder.

This is actually a very serious consideration. Because I miss having a welder for steel, and I think it would be better to have a second unit for aluminum. Just need to see with my own eyes that the sp125 won't do the job. Then I'll respool it for sheet steel.

I suppose I'll need a 220v outlet in the garage too. Unfortunately I'm eyeing up the miller synchrowaves...

One step at a time.

[handyandy]

If you want to spend the money on the synchrowave go ahead they're great machines. I couldn't justify that much money for a welder as a hobbiest home shop welder. I've been really pleased with the hobart 190 I have. The spool gun works great did a great job welding the 1/8" thick aluminum for my transom extension have also welded some 3/16" thick with it. It does very well on steel as well. When I first got it I was worried I wouldn't like that it doesn't have infinitely variable voltage settings, but honestly it's been great I haven't encountered anything I couldn't weld well on one of the settings. If you can afford better, you won't regret it, and I'm the sort of person 220 is a requirement in my garage between air compressor, lift, welders, and plasma cutters you can be so much more capable with 220v in a garage.

[handyandy]

I have both tig and mig machines I wouldn't give up either, for new aluminum that is .090 or thicker I prefer my hobart with a spool gun any day over my tig. You can burn in a good weld so much quicker, but it doesn't replace a tig. The tig is great for welding anything, especially repairing old thin jon boats for people the mig just can't weld the thin varying thickness of old thin aluminum. It's also great for welding cast stuff assuming it's a decent casting of good material. Some castings are just garbage and near impossible to weld. One of the syncrowaves would be awesome 115v and 220v capable, AC or DC, mig, tig, and arc all in one package would be awesome. I have my tig and mig set up on one cart with both an argon and C25 bottle I call it my poorman multi process machine.

This would be awesome to have.
https://store.cyberweld.com/misy210tico9.html

[86tuning]

And, because I finally got back in the garage to pull the carbs for the Nth time, I took pics of the grease hose. Just because it confused me for a while. Unfortunately I'm becoming well versed with pulling the exhaust manifold.

The grease hose to the support bearing. Which, of course, has never had grease in it, for the first 18 years (56h) of it's life.

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The location on the exhaust manifold to apply grease with your grease gun. After every rip on the water.

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And where the hose connects to the manifold, secured with a tie wrap (or ziptie)

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[86tuning]

I had problems with th 'pop-off' springs, made it run bad at midrange. There is a pressure test foir pop off you might want to do.

Good luck.

Ahh, struck gold here. Will check the pop off once I figure out how to secure my bicycle shock pump to the fuel inlet. Cheers, first round is on me if we ever meet in person.

- Brian

[CedarRiverScooter]

Glad you are making progress.

Another failure mode I discovered (the hard way). If you over pump grease into the bearing carrier, it pushes out the seal. Then you get to pull the pump & shaft yada yada

[86tuning]

I found the mikuni service manuals here:
https://www.mikuni.com/c-manuals.html

So according to what I could glean on the web, popoff pressure is supposed to be set at 45-55psi.
edit: stock needle seat is 1.2mm, and stock popoff is 75psi.


Well I don't have a pop off gauge. But I have a few bicycle shock pumps. As far as I can tell, a popoff gauge is a bicycle shock pump with a hose on the end of it. And the typical $60 popoff gauge is about 2x the price of a typical bicycle shock pump. Pics on the web show a similar type of pump. So my ghetto rig should work exactly the same as the special factory tools.

My bike pump threads onto a schraeder valve (tire stem). So I took a tire stem, shaved the rubber a bit to fit a piece of hose. Took the valve core out, and then threaded the adapter onto the hose of my shock pump to make a pop off gauge. Yes, a 0-60psi gauge would have been ideal. But my gauge should be repeatable enough to get both carburetors to the same setting.

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[CedarRiverScooter]

You could sell that!

[handyandy]

some fine redneck engineering I like it.

[86tuning]

Well, I learned more stuff about carburetors. Turns out that I'm not running the SBN44 but rather a BN46i which is the carburetor that's specifically tuned for emissions. Not a big deal on my end, but that means the popoff results aren't what I was expecting. Also means that I will not be modifying this engine at all so that I don't have to deal with attempting to performance tune the carburetor. Because that would be an uphill battle. Searching on greenhulk got me the deets.

fyi. fuel pressure is 1-6psi depending on engine speed and load.
stock needle seat is 1.2mm. When I looked in there, it looked a lot smaller than the 1.5 hole I was expecting.
stock popoff is 75psi.

So, my bicycle shock pump would have worked fine for a normal carburetor where the popoff is 45psi or lower. But in my case, the fuel pump body leaks at 40psi. Which isn't a problem, because fuel pressure is <10psi. So I'm good to go. Would have been nice to have the experience to know this, but hey, experience is what I've gotten, right after I needed it most. Haha.

I ended up using a tire filler with gauge to check popoff pressure. I simply put my adapter hose into the tire pressure gauge, and slowly added compressed air until the needle popped at 75psi. I ignored all the air leaks on the pump side. And managed to wrinkle the clear pump diaphragm sheet. Had I known that would have happened, I would have used a rubber tip blow gun to apply pressure directly to where the little fuel filter screen mounts to avoid damage. It's not cracked, so likely will still be functional enough for now.

After I tested popoff (thanks scooter) and confirmed that both carb needles are popping at the same pressure, I decided to explore the insides of the carburetor a bit more, and checked the jets by spraying some carb cleaner through the jet to confirm that the passages to the carb throat were clear. Which they were. I also examined the anti-siphon valve flap, which was fine on the rear carb, but not sitting flush on the front one due to debris/varnish. Removing the flap shows that it had a permanent bend.

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Hopefully this valve was the cause of my running issues. It does start easier now, and revs nicely on land. Can't wait to water test it again.

If you want to make your own popoff gauge, a yoga ball fill adapter will fit into a tire fill gun or bike shock pump. Add a piece of hose and you're good to go.

[CedarRiverScooter]

86, I think you are our resident diaphram-carb expert now!

[86tuning]

86, I think you are our resident diaphram-carb expert now!

far from expert. it would just be the blind leading the blind <grin>

I have done a bunch of reading over the last several weeks though. The mikuni owner's manual that I found here

https://www.mikuni.com/c-manuals.html

has tons of info on how the carbs work, and how to set them up to work properly. Highly recommended reading for anyone who wants to figure out how carburetors work.

I took a couple of videos of popoff testing, but can't seem to upload them here

All giddy about getting this thing on the water for testing. Will take my toque off this time so that it won't blow off at speed.

- Brian

[86tuning]

Success on the water! Ran great, me and a buddy had fun hooning around for an hour. Started immediately every time, no stalling. Ran good at idle, and accelerating through mid and high speeds. Strava said we hit 75kph (40 knots) so it rips pretty hard. Next step, teardown and measurements, then order materials and start cutting. I wonder if my little SP125 will even penetrate the 1/4" thick pieces of my water inlet. Haha.

Getting excited. Only took 5.5 months since the first water test.

[CedarRiverScooter]

On my 1st iteration, I used a cobbled-up welder (never designed for alum) & in retrospect it tripled the time it took to put boat together. Last time & had a spool gun machine & TIG. Did 10X more welding in 1/3 the time. Plus I can trust the welds.

[turbotodd]

Welding Aluminum with a MIG is fun, but if you're doing anything thicker than 1/8" you need a bigger welder.

Why? Because aluminum is a big heat sink. The arc is what creates the heat needed to melt the metal. With aluminum, it dissipates the heat so quickly that you need more arc voltage (with MIG) to melt the metal than you would if you was welding mild steel.

Lot of guys say it can't be MIG'd, but it sure can. I've built many projects with an old Lincoln Weld-Pak 100, with a spool of aluminum wire and 100% Argon. 99% of the time the voltage was turned ALL the way up, as was the wire speed.

With Aluminum, it's sorta backwards. Generally speaking if you're burning holes, you're going too slow and need more heat. Sounds odd but that's been my experience. TIG is a little different obviously, but same principles apply...especially with heat needed. 200A TIG unit will be max'd out with 1/4" aluminum and I mean MAX'd out pedal to the metal and feed plenty of filler as fast as possible.

Clean clean clean! Aluminun needs to have EVERY ounce of clean put on it. Why? Aluminum oxidizes quickly (that's the white stuff you see on Al that's been sitting outside for a while). The oxidation...Aluminum Oxide...melts at around 3700 degrees F. The aluminum itself melts at around 1200 degrees. See a problem? Then dirt...grime, grease, etc...all will adversely affect the quality of the weld. The weld in the picture above has a little junk in it, but otherwise looks pretty good. Better than I can do but I'm no pro..FAR from it. My eyes are getting worse and that's affecting my welding skills severely. When I say clean, I mean clean the contact tip (or tungsten if using TIG), clean the filler material (wire/filler rod), clean the base metal, clean all metal to be welded, and everything within 1 inch of the weld. I even clean the table I'm welding on because I've had instances where something was on the table and spattered into the puddle while welding. That's always fun to figure out. If you use a wire brush, use a known clean one made specifically for cleaning aluminum, and use it for NOTHING else until you're done welding. IF TIG, grind your tungsten on a wheel that's fresh and will not be used for anything else but grinding aluminum welding specific tungsten as if you grind something else, it gets embedded into the rock and will make its' way to the tungsten-contaminating the puddle, and throwing you for a loop. Fun stuff. You'll get good if you do it enough.

The jet jon idea has me intrigued, big time. I want to watch some of these threads. Used up/wrecked jet ski's are everywhere out here, and dirt cheap.