Runs great on trailer, but not in water

[B_Zeddies]

I have a 95 750 sx with a single 46 SBN on it. The ski runs and idols great on the trailer but as soon as we put it in the water and give it throttle it doesn't rev up and take off. It stays at a steady slow pace, doesn't die but again doesn't take off either. Tried tuning the carb and it doesn't make a difference. Also changed the main jet to allow more fuel, still doesn't fix the problem. Any input would be greatly appreciated!!!

 

[Big Kahuna]

Is it cavitating?

 

[B_Zeddies]

It is not cavitating, it just falls on its face once under load. Prior to changing the main jet, as I would take off it wold be slow and then gain full power and feel solid. Once I slow down or make a turn it seemed to fall on its face again until I slowly gave it throttle and then would pick back up and take off.

 

[Big Kahuna]

Jetting/pop off is "off"

 

[kevbo]

You installed a larger jet and it made the problem worse? Try a smaller jet.

 

[B_Zeddies]

Jetting/pop off is "off"

Checked the pop off and was only at 11, got new jets and a new spring. Runs the best it has on the trailer, testing this weekend on water!

 

[Flash-FX]

Did it ever run good? Is the motor all stock, no mods like head & pipe??

 

[fastgtfairlane]

Have you tried a leakdown test to verify you don't have an airleak somewhere in the engine?

 

[WFO Speedracer]

It is also very possible the stator is bad on that ski, it gives kind of the same symptoms as fuel issues, if you can choke it and get it to take off it's the carb if it still won't take off check your stator.

 

[MarkWalker]

A friend of mine had this same problem with his Superjet. Chased it for 2 summers. Split the cases and found a bad crank bearing. Replaced the crank. Problem solved!

 

[Myself]

Could also be sucking air from cracked fuel pickups. Just another thing that needs checked out.

 

[B_Zeddies]

A friend of mine had this same problem with his Superjet. Chased it for 2 summers. Split the cases and found a bad crank bearing. Replaced the crank. Problem solved!

It is a brand new crank so I really hope that isn't the issue, will check it out if it doesn't respond well after this weekend. Found the reeds to have big gaps in them so hoping that was also a contributing factor to my problem!

 

[B_Zeddies]

Did it ever run good? Is the motor all stock, no mods like head & pipe??

It ran great prior to rebuild. Ski caught on fire and then pulled apart and found a bent crank as well. Ski has a single SBN 46 carb, PJS intake manifold, big pin piston, factory pipe with a factory exhaust manifold. Carb has a 120 pilot jet in it now with a 145 main jet, 2.0 needle and seat with black spring. Found the reeds to have some hefty gaps, got new reeds and testing once again this weekend.

 

[Flash-FX]

Bad reeds normally give a false rich condition. If everything else was good, the new reeds should clean & crispen things up. Good luck


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