Fuel/Carb issue

[95sportster]

Hi all. This is my first post so hopefully I wont sound like an idiot. Im a noobie to seadoos so if I do then I guess thats my excuse. I did a search on this but didnt see exactly what I was looking for.

I just bought a used 95 sportster with the single 2 cycle rotax with dual mukuni carbs. The boat is very hard to start in water. It runs fine on the trailer but once it gets dropped in the water, it struggles to start. It turns over just fine, so its not a battery issue and it has spark. The issue is the fuel. I dont think while starting the engine that the fuel is being pumped through the carbs, however, if I play with it enough or if I just get tired of fooling with it and pour gas down the carb and it starts, it runs perfectly fine. I took it out today for the 3rd time (the first 2 times ended in me being towed back because I stopped to swim and couldnt get it started back) and I started it on the trailer before I dropped it in the water. It hesitated but eventually started in the water and I drove it around for an hour or so, with no issues. I bring it back and through the no wake zone, I have to idle it and it doesnt want to go that slow and shuts off. So before it get suggested, I did adjust the idle screw and I noticed little to no difference in its behavior. Its something to do with the low speed or low vaccum maybe??

Is this as simple as adjusting the carb or do I have an air leak in the lines somwhere? Also, I dont know if this is related but the fuel tank vent on the outside of the hull is not a check valve like I was expecting. Nothing is stopping air from coming in and out of the tank and only the loop in the line is keeping water from the tank. Is this normal or is there supposed to be a oneway valve in the vent line?

 

[sunbaby69]

does it crank fast or slow? if slow, might be starter or pump but uit sounds like fuel delivery issue, check all fuel lines. if no luck, pull carbs and clean-there is internal filter in carbs that requires cleaning

also, is drive pump ok since it wont start under load.

 

[95sportster]

does it crank fast or slow? if slow, might be starter or pump but uit sounds like fuel delivery issue, check all fuel lines. if no luck, pull carbs and clean-there is internal filter in carbs that requires cleaning

also, is drive pump ok since it wont start under load.

Thanks for the reply. Better late than never Ive since "fixed" the issue though.

I rebuilt the carbs with new seals, needles, seats, etc. I set the pop off pressure correctly. I believe the pop off pressure was the culprit. It was set way too high I found out. I cleaned out all fuel lines and the fuel selector valve. It idles much better now. It also made a ton of difference in the acceleration out of the hole. It really jumps out now and planes quickly.

It is still hard to start though. The battery turns the motor over fine, it just might take 15-20 seconds for it to fire up in the water. On the trailer it fires up instantly.

 

[sunbaby69]

they are always harder to start under load(in water).. not a bad idea to remove venturi and pump cone to check pump out though...

 

[95sportster]

they are always harder to start under load(in water).. not a bad idea to remove venturi and pump cone to check pump out though...

Im assuming to check out the wear ring and impellor? I plan to, but I probably wont get a chance until the season ends. Could a bad wear ring/impellor make it harder to start? I understand about the loss of power/ cavitation issues.

 

[sunbaby69]

impeller/wear ring wont usually cause hard start, just cavitation issue. Bad pump bearings could be cause of the hard start!!