Fuel issues with 787cc engine.

Not open for further replies.


New Member
Need some advice.
I own a twin engine 98 seadoo speedster.
Im having issues with the starboard engine.
It runs great for as long as its at wot once the throttle is returned to idle it dies and won't start again for 20 min or so. I replaced the fuel pump and all new lines. Carburetors was kitted by a trusted marine technician. Im stumped!
Anyone have any issues like this?
Well... There’s a lot of confusing information in this post. These carbs don’t have floats or tabs, so they are definitely not the problem. There is also no fuel pump to replace on these boats, as they are operated by a vacuum operated diaphragm inside of one carb housing on each motor. I’m not sure what you could have replaced without pulling the carbs apart yourself, other than maybe the fuel baffle inside the tank where the sending unit is.

The fuel system is the root cause of most of the problems we see on these motors, so you need to stop trying to run it until everything is sorted out. I would start by rebuilding the carbs again with GENUINE Mikuni kits and new needles and seats. Do not buy aftermarket carb kits! You’ll be chasing problems forever until you wind up just buying the Mikuni stuff and doing the whole job over again. While you’re at it, replace the fuel selector and the water separator o-ring as well, as they are a common place for problems. I don’t believe the Speedsters came with Tempo fuel lines, but if you see any grey fuel lines, they need to be replaced before you rebuild anything else, and before you run the motor again.
Anytime! They are the Mikuni kits and not SBT or another aftermarket brand right? I know it seems trivial, but there’s a huge difference between them that isn’t apparent when looking at them.

When you get ready to rebuild them, go through the carb rebuild sticky at the top of the 2-stroke PWC forum, and follow those instructions to the letter. It’s a simple job, but it’s got to be done right or the boat will never run the way you want it to.
I have a question.
What spring should i use. Im not sure if the last person that kitted these carbs put the right spring in. The thread says "do not use the springs in the kit"
It says to use the black 80 gram spring but were do i get it? The spring that was in it is different from the two in the kit. And its not black.
I just started kitting the carbs but I'm hung up on the spring for the needle/seat. Lol i don't want to keep chasing my tail because of a $.20 part.
You can get the correct springs from Westside Powersports Seadoo, OSD and PWC Muscle. The old 80 gram were a dark army green and the new ones are black,
Carburetor kits done. Had to order the 80 gm. springs separately but it was worth it.
Lake test went great!
Boat runs 58 mph!
Now the bad:
Shift cable broke and when i was trying to get forward to work i ended up breaking the shift leaver on the gate as well.
Back to ordering more parts.

Thanks for all the help and hospitality!
As a little tip that hopefully saves some frustration, make sure you’ve got a proper sized screwdriver for the lever mounting assembly before you pull it out. Those screws are really easy to strip out and a major pin to drill out once they’re stripped.
Not open for further replies.