Seadoo challenger 1800 787 engine stalls when increasing throttle

[zmanders]

I have a seadoo challenger 1800 with the two 787 motor. One of the motors stalls when I increase the throttle. I've tried adjusting the jets on the bottom of the carbs, but still no luck. The motor idles fine and will all day long, but stalls out when I go to accelerate. Please help I'm not sure what the problem is. It also seems to rev higher out of the water, but won't when in the water.

 

[Elliott Winter]

Hi Zmanders
I'm by far no expert, but i notice that i have a similar problem on my 787 jetski when the spark plugs go bad and get a lot of carbon build up. I was getting no performance where one plug had gone bad.
I'm sure you would have done it already but have u checked ur plugs

 

[Dr Honda]

It could be bad plugs... but generally the engine won't idle either.

It's time for a rebuild on the carbs. Also... make sure there isn't an air leak in the filter bowl. (a bad O-ring can cause that problem too)

 

[zmanders]

Thanks! I'm going to check things over and see if I can find anything. Do you think the high speed jets could be out of place?

 

[Bills86e]

Unplug the connector for the lanyard post and clean it, then clean the inside of the lanyard itself. Then try it again. You can also clean, dielectric grease and test all fuses, wire connectors, and grounds, unplug the magneto connector plug and clean it too. Hopefully you just have a corroded terminal somewhere that is breaking contact and cause of the stalling.
Besides grounds, fuses and fuse holders, the main places to be concerned with are the innards of your coil box, and all igniton related connectors, including the stop start switch and lanyard post, mpem, cdi and coil connector.
Worst case senario is a bad ignition pickup in the magneto housing that may be broken or is covered with metal debris and is getting shorted out

Unplug the connector for the lanyard post and clean it, then clean the inside of the lanyard itself again. Then try it again. You can also clean and test all fuses and grounds, unplug the magneto connector and clean it too. Hopefully you just have a corroded terminal somewhere that is breaking contact. If not, more diagnostic work will need to be performed.

Besides grounds, fuses and fuse holders, the main places to be concerned with are the innards of your coil box, and all igniton related connectors, including the stop start switch and lanyard post, mpem, cdi and coil connector..
Worst case senerio is a bad ignition pickup in the magneto housing that may be broken or is covered with metal debris and is getting shorted out.

A free floating piece of metal inside the mag housing can short out the system regularily, or irrregularly, depending on what it touches. If it is not a broken gear tooth or starter shaft spline, it could be a piece of the centrifical weight holder retainers inside the bendix, as they break off regularly and there are 6 of them. They are U shaped and about 1/4 inch long x 1/4 inch wide. Not only a huge hazard to the destruction of the stators coils, but also a hazard to the ignition pickup by gounding it out killing spark and the power to everything else.

 

[zmanders]

Ok I took it out in the water today to test it after I cleaned the low and high speed jets. cleaned and checked the electrical system and seems to be working fine. The motor will idle perfect and will not stall. I can go full throttle with the carb wide open and it won't stall either, but will not rev all the way to the limiter. When i put it in the water it wont rev high enough to help the other motor get the boat on a plane. It acts like I’m only giving it 1/4 throttle. Any ideas from this point?

 

[dsw222]

Ok I took it out in the water today to test it after I cleaned the low and high speed jets. cleaned and checked the electrical system and seems to be working fine. The motor will idle perfect and will not stall. I can go full throttle with the carb wide open and it won't stall either, but will not rev all the way to the limiter. When i put it in the water it wont rev high enough to help the other motor get the boat on a plane. It acts like I’m only giving it 1/4 throttle. Any ideas from this point?

Did you use rebuild kits when you put your carbs back together? Or did you just remove the flame arrestor, take the carbs off the boat, open up the carbs, and spray cleaner inside of the carb bodies?

Maybe a gasket isn't sealed right and you have an air leak?