300/440/550 Build Thread: Yamaha Superjet motor in a Kawasaki 550sx hull

[rwilliamtaylor]

We just pulled the Yamaha 6m6 (650) motor from our SN Superjet and dropped a 61x 701 in it.

We've been thinking about a Kawi 650/750 conversion to replace the 550 piston port motor thats in our 550sx now because i'm 6' 4" 215 and the skis a bit undepowered even though the 550 is pretty modified. The yamaha 650 ran great so why not put it into our 550sx hull and create a unique ski.

After a bit of investigation I learned that Rhaas products is working on a conversion kit that should do the trick.

First the before pictures...
The Superjet that the 650 came out of and the 550sx it's going into...

Before engine bay...

Here's the Superjet Motor. It's complete with ebox, carb, exhaust, starter, bed plate.

The Rhaas Products kit will have a new coupler that goes on the Yamaha motor and mates up to the 550 drive shaft coupler so the Yamaha coupler has to come off. I was a bit worried about getting it off since the Superjet was run in salt water at one point in its life. About a week of soaking it with DuPont Teflon penetrating oil and a couple of light whack with a hammer and it spun right off...

Note the difference in size between the stock Yamaha coupler and the stock Kawasaki coupler.

 

[rwilliamtaylor]

Hull prepped for the conversion kit

Here's the old 550 PP motor beside the Yamaha 650 motor

While everything was out I decided to relocate my bilge pumps

Remove the 550 motor mounts...

Here's the Rhaas products conversion kit. Parts are really well made with a nice powder coated finish.

First step is to clean up the threads in the hull...

Now cut away the front and back of the battery box to fit the new battery tray...

 

[rwilliamtaylor]

There are a couple of places where the hull interferes with the bolts for the motor mounts. I marked them with a sharpie and then used the dremel to grind some material away.

Now bolt in the conversion plates...

Now attach the new Rhaas Products motor mounts...

Heres the adapter coupler to attach the yamaha motor to the Kawasaki drive shaft... Just a test fit!

Mounted the coupler to the Yamaha motor

 

[rwilliamtaylor]

Before mounting the battery box bracket which moves the battery back enough to clear the intake runner, you need to deepen the holes for the longer crews using a 3/16 th drill

Install the battery box bracket...

Now install the ebox bracket.this is where I run into a snag. I have a primer kit and the back of the primer interferes with the ebox bracket.

I also have dual bilge pumps and the ebox bracket interferes with both of the bilge hull fittings.

Solution... I moved the bilge fittings being the ebox.

Hmmmm.... What to do with the old holes.

Solution... Installed a shorter bulb style primer

Ebox installed... Tight fit...

Gas tank just fits as well... Might have to try an aftermarket pipe later.

The exhaust has to be reduced from the larger Yamaha hose to the smaller Kawasaki hose to the water box.

 

[rwilliamtaylor]

Plumbed in the new fuel lines... Went with some sexy orange ones this time...

Now wired up the Kawasaki start stop switch to the Yamaha ebox using shrink wrap style waterproof connectors

The coupler cover would not fit without being shortened by about 4 inches.

Throttle cable attaches with no modifications at all

 

[rwilliamtaylor]

The hood needed to be modified because the vent tubes interfered with both the exhaust and intake runner.

Before

After

IT'S DONE! Started right up and ready for the test run.

 

[rwilliamtaylor]

Ooops forgot about the battery....

I picked up a new battery that is shorter than the one I had and fits the bracket perfectly. My battery straps were too longer so I tie wrapped a dowel in the middle to shorten them

 

[rwilliamtaylor]

Took it for a ride today and it RIPS!

Im 210 lbs and this ski with the modded 550 motor would barely pull me out of a tail stand. Witt the yamaha motor it has no problem. Here's a video of it running... OK... no smart remarks about me falling off... Seems I can't turn and look to be see the pisser is running at the same time.

http://www.youtube.com/watch?v=MneRoDOxvOw&feature=youtube_gdata_player


I also raced my son (160 lbs) on our modded 701 Superjet. He was just barely pulling away from me... I'm surprised how fast this ski is now. The Superjet has a ton more low end hit though.

 

[rwilliamtaylor]

The mods continue... I'm going to put a factory pipe manifold with a 650sx Westcoast pipe on it, but first it needs more room for the pipe so I swapped out thenoem gas tank for a kart tank.

Old tank is a tight fit...

Kart tank I got off the x-h20 classified...

 

[Yami-Rider]

very cool! keep up the good work!

 

[ph1lthy11y]

Good job man . What lake was that in the video ???

 

[rwilliamtaylor]

Good job man . What lake was that in the video ???

It's the El Capitain Reservoir near lakeside CA. Great place to ride... The rangers are pretty cool and they allow freestyle riding. No rules about only riding counterclockwise or any other "suck the fun out of it" rules.

 

[rwilliamtaylor]

I got the Factory Manifold and 650sx Westcoast pipe and tried the install. It doesn't quite fit, but I think I can modify it to make it fit, but I need some advice. Can you bend a Westcoast Pipe like you can a Factory Pipe? Here's the problem...


Manifold...

Here's the pipe...

The first place it contacted the hull was the little tab, so I ground it off...

Now it still hits the hull ( Noy by much) where it marked...

The question is... Can i bend the pipe to get the clearance I need?

 

[Yami-Rider]

That is cast aluminium and it will just crack if you try and bend it. Best bet is modify the hull.

 

[dbattersby20]

I was wondering if a b pipe would fit though. Im in the middle of a similar project and wont be getting the pipe until late spring. But want to finish up the hull work before that. Also, im impressed that a conversion kit worked because i completely ground out the motor mounts from the hull then used i think half inch aluminum and super jet mounts and was just able to fit in a 61x and that was with a a different pump which sits up higher.

 

[davy87nj]

Whats done to the pump/impeller on this ski?

 

[rwilliamtaylor]

Whats done to the pump/impeller on this ski?

It is a 550sx pump with a Solas 13/18 prop, a freestyle pump cone and a bored nozzle.

 

[rwilliamtaylor]

I scrapped the Westcoast pipe idea as ir just wouldn't fit. Now I'm running a Factory Pipe manifold and 650sx pipe with a dry pipe modification. Fit real nice and really wakes up the motor over the stock exhaust. Now that it runs so well, I'm going to paint the head pipe so it looks a bit better.

 

[davy87nj]

This is a cool build. I got a solid JS550 hull and a Yamaha 650 engine right now. Going to look up that conversion kit for sure.

 

[loictahiti]

Waoouh cool build thread and tutorial thread

Nice job

So, for the swicht start stop connector, you could keep the end pin terminaison from kawasaki start stop wire , just take out the plastic cap and plug the pin in the yamaha plastic cap they fit wery well , just the plastic are different, the inside pin are same . Next time for you

So , how many you paid your conversion kit from Rhaas ? A friend of me wants to switch is 550 engine for 650/700 yamaha engine

Thanks a lot