Bowser's WaveRunner

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This WaveRunner 500G is now a part of my vintage flotilla.
I found it listed for free an hour from home- so with my EZLoader trailer I made the trip to pick it up. The man offering it was very generous; we chatted for an hour, walked his property, explored the waterfront he was on, and even took home a couple house plants he grew!
Story goes he bought it for cheap from a friend a few years ago with intent to restore it once retired but has too many other projects on his plate, so here we are. Last time it was registered was year 2000.


It's from 1988! Come to find out this model is part of jet ski history. It’s the first iteration of a seated jet ski.
35 years has done its damage but inside the hull is surprisingly clean. Since poking around in it I’ve found it has a modified air intake to fit a larger pod style flame arrestor. The 34mm Mikuni carb has been modded too by having the choke butterfly valve removed. I'm not sure what to expect for how this will affect performance-


SO the compression testing yielded 150 psi on the MAG and ~130 - 100 psi on the PTO cylinder. This was cold testing with a squirt of oil down the plug holes, charged battery, and WOT.
Despite less than stellar results I think I’m going to proceed with the restoration.
The motor smoothly rev’d up with some premix and new plugs! I’m eager to get the carbs restored and titling/ registration solved.

I know this is SeaDoo Forums but I’m sure there’s lotsa cross-over knowledge & appreciation.
Cool find but your history is a little off.

First was the 1969 Seadoo

The first Japanese were the 1987 Kawasaki X2...
And 1987 Yamaha WR500
And Wave Jammer 500
Alrighty I have the carburetor cleaned and ready for rebuild. Awaiting on replacement washers for the mixture screws to come in the mail. I asked ChatGPT what to expect not having a choke valve and it found issue with cold starts mostly.
Finding repair data can be a bit tough so I will be uploading notes here for reference as I go.


Funny enough I was stuck finding a replacement hull drain plug that fit- turns out these models did not come with a drain from the factory, it was modified later on this ski.
Just need to test if the motor can stay running next!


Cool find but your history is a little off.

First was the 1969 Seadoo

The first Japanese were the 1987 Kawasaki X2...

And 1987 Yamaha WR500

And Wave Jammer 500

Those first two models are so retro wow. The Kawi almost looks like the front of their Snowmobiles. 😄 The Yamaha webpage mentions this WR500 is the first seated style ski with an “open stern” feature- maybe that's the differentiating factor although that X2 sure looks like it.
Carburetor is all replaced and clean. Using Genuine Mikuni kit plus the proper 2.5 seat + needle.
I did not pop off pressure check it but left the needle valve arm resting gently on the needle w/ the other end level to the surrounding metal. It’s a gamble I know- if it runs poorly or not at all this may be a suspect.
Mixture screws set to: Low Speed: 1-1/4 :: High Speed: 3/4 out from seated.


I replaced the outer JIS screws with Allen screws and it looks reeaal nice matching the chrome high flow intake adapter.
Assembling this carb was interesting cause of the round pancake stack it forms by the end.
Pictured is the brass nipple that was added aftermarket in place of the choke valve.
It runs !
It 2-stroke runs away!

Testing on the trailer, I got it to fire up well after a couple cranks. Let it run for a few seconds then stopped it.
When it started up again I could tell it was revving past normal so killed it via stop switch. Tried it on the hose and it revved with no response from the throttle- killed it via switch.
The boat was out of the water PLUS no flame arrestor at the time PLUS my fiddling with the mixture screws probably caused this run away. Hoping to get it in the water this weekend. Awaiting the pre-filter in the mail, it'd be nice to test with this on too.

I slipped on the aftermarket flame arrestor and boy does it look mean. It's neat to look down the throat of the intake through the top.

Keep in mind you are going to be lean as the carb is designed to work with the restriction of the stock aircleaner.

A lean 2-stroke is a dead 2-stroke.

I would also get high quality zipties for the fuel lines as the colored ones are typically cheap and a fuel leak can be explosive.
Good points, I'm hoping to get some wisdom to prevent lean seizure..
Assuming I should open the mixture screws more to accomodate for the aftermarket mods allowing more airflow. Should I also adjust the premix ratio too?

Good eye on the zipties- was thinking that I need to replace with SS hose clamps.
Yarrgh ! It works!
Check the video to see the massive exhaust leak in the hull lol.

I took a better look at the exhaust manifold and sure enough the gasket was blown straight through. Now I’m stuck mulling over how best to lift out the motor for exhaust gasket repair…

I didn’t run it much longer than shown in the clips. Started up with a little priming, appropriate amounts of smoke shot out the back then reduced while on the trailer.
I let it run at idle while puttering about but when I held it WOT it did not pick up speed so I guess that’s a high-speed screw issue?

While returning to the trailer I felt the steering cable herniate through the shielding so that’ll be replaced as soon as I tackle the gaskets.

I guess this is a lift point for the motor, shown with arrow. I’ll look around more for a second proper lift point but any suggestions would be appreciated.


I’m just relieved I know it runs. Felt like sitting on a RC boat it’s so small.
Prepping for removal of the motor to replace the exhaust gasket..
I just bought a used engine hoist since it seems the restoration bug has bitten me. ;)
Thankfully SBT has a removal guide and I gained some confidence since removing the SPX’s 657x motor this past spring.
Wishing access to the motor mounts isn’t too much of a PITA.

As summer winds down the humid weather really brings out the mosquitos that make working on the ski’s a no-go. Hoping I’ll get this WR500’s motor out before fall now that I have the proper hoist.
I visited with fam in upstate New York this past weekend. They live on a big lake up there and let me drive their WaveRunner VXR. Man that thing was FAST. I reached top speed of 70mph with ease but what was more impressive was the acceleration holy smokes if my finger squeezed that throttle too abruptly I probably would have fallen off. Plenty of incentive to get one of my skis running.

Speaking of.. I am still in the process of loosening the motor mount bolts on the WR500. Using a buddy’s extended reach ratchet I got one of four loose- just need to take another crack at the others. Those power ratchets don’t have as much torque as I’d like but I refuse to bust another knuckle on this thing until it’s my last resort.