96 Polaris SLT780 issue/question

unixdood · 06-12-2014, 09:22 AM

Hi all, new here and I have a weird issue that I am really hoping someone can help me with. The jetski starts and runs great, good water circ, no overheating. Everythign works as it should. I launch into the lake and this is where it gets weird.

At idle in fwd and rev it moves fine, I give it throttle and it has a good hole shot but then.......Its almost like when your in a car and the clutch is slipping, thats what is happening to the polaris, it will start off great then the engine will over rev but the ski will stop going forward.

I am looking for any ideas on this? Where to check and what it may be? please anyone help. Dont want to go the whole summer without the ski.

Thanks
Bill

LIforrelaxin · 06-12-2014, 09:34 AM

If I understand the system correctly, which are your engine is running fine, you can launch and accelerate, but at some point, the acceleration and forward momentum slow and eventually stop, with the engine over revving.

Sounds to me like a drive train problem. Could be as simple as the impeller hub slipping... or it could be something else in the drive train. Unfortunately I don't have much experience with the particular jet ski... there could be couplers in the drive system that could be failing etc. All these of course in place, so that if you jam the pump, you break a sacrificial part before damaging the motor etc.

If you are not super mechanically minded I suggest bring the jet ski to a shop to let them evaluate it.

unixdood · 06-12-2014, 12:15 PM

i can pull the engine or pump or whatever, Its not that im not mechanically inclined, just looking for a starting point as I have never experienced this before on any other jetski I have owned.

I know there isnt a clutch or anything, so maybe your right that the impeller is slipping but still, that should be on a spline shouldnt it?

Could it be the wear ring causing it? I didnt think so because the hole shot is fine so its got great pressure out the jet pump.

SIKSUKR · 06-12-2014, 01:02 PM

Never heard of a clutch, should be direct drive. If it sounds like its cavitating I would look to see if the impeller is worn and there is too much clearance between that and the housing. If it doesn't cavitate I would look at the impeller slipping on the driveshaft.

Winnaholic · 06-12-2014, 07:01 PM

I had that same problem on a Sea Doo GTX. I tried to figure it out like you and I'm mechanically inclined, turned out to be the impeller was spinning on the spline of the drive shaft. The teeth on the spline were worn and under acceleration the impeller would slip. What got me was there was no noise that you would expect like grinding, I finally got help with it from the boys at DeSilvas, ended up replacing the drive spline and impeller. This sounds like your situation, hope the info helps.

WeirsBeachBoater · 06-12-2014, 07:17 PM

Inspect your impeller, and the space between it and housing. Sounds like cavitation usually caused by damaged impeller. Polaris doesn't have a wear ring like seadoo.

bilproject · 06-13-2014, 05:58 AM

the coupler between the crankshaft and impeller shaft is bad. Impeller housing has to be removed with shaft and coupler untreaded from back of engine. You will need to remove spark plug and feed a small piece of rope into a cylinder to stop the motor from turning over while you break the coupler free with a pipe wrench. the coupler is right hand thread. You can find a parts breakdown on line. Once you identify the coupler you will see that the repair is not too hard. Hardest part will be finding parts as Polaris parts are no longer made. You will also need new gaskets and orings as long as you have it apart replacing the impeller would not be a bad idea.

unixdood · 06-13-2014, 06:02 AM

thanks everyone for your input. I will be tearing down the impeller this weekend. Ill let you all know what the deal is when im done!

06-12-2014, 09:22 AM	#1
unixdood Junior Member Join Date: Jun 2014 Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	96 Polaris SLT780 issue/question Hi all, new here and I have a weird issue that I am really hoping someone can help me with. The jetski starts and runs great, good water circ, no overheating. Everythign works as it should. I launch into the lake and this is where it gets weird. At idle in fwd and rev it moves fine, I give it throttle and it has a good hole shot but then.......Its almost like when your in a car and the clutch is slipping, thats what is happening to the polaris, it will start off great then the engine will over rev but the ski will stop going forward. I am looking for any ideas on this? Where to check and what it may be? please anyone help. Dont want to go the whole summer without the ski. Thanks Bill

06-12-2014, 09:34 AM	#2
LIforrelaxin Senior Member Join Date: May 2006 Location: Texas, Lake Ray Hubbard and NH, Long Island Winnipesaukee Posts: 2,871 Thanks: 1,037 Thanked 892 Times in 524 Posts	If I understand the system correctly, which are your engine is running fine, you can launch and accelerate, but at some point, the acceleration and forward momentum slow and eventually stop, with the engine over revving. Sounds to me like a drive train problem. Could be as simple as the impeller hub slipping... or it could be something else in the drive train. Unfortunately I don't have much experience with the particular jet ski... there could be couplers in the drive system that could be failing etc. All these of course in place, so that if you jam the pump, you break a sacrificial part before damaging the motor etc. If you are not super mechanically minded I suggest bring the jet ski to a shop to let them evaluate it. __________________ Life is about how much time you can spend relaxing... I do it on an island that isn't really an island.....

06-12-2014, 01:02 PM	#4
SIKSUKR Senior Member Join Date: Apr 2004 Posts: 5,075 Thanks: 215 Thanked 903 Times in 509 Posts	Never heard of a clutch, should be direct drive. If it sounds like its cavitating I would look to see if the impeller is worn and there is too much clearance between that and the housing. If it doesn't cavitate I would look at the impeller slipping on the driveshaft. __________________ SIKSUKR

06-13-2014, 05:58 AM	#7
bilproject Senior Member Join Date: Oct 2007 Location: Bear Island/Fort Myers, Fla Posts: 229 Blog Entries: 1 Thanks: 1 Thanked 59 Times in 41 Posts	coupler is bad the coupler between the crankshaft and impeller shaft is bad. Impeller housing has to be removed with shaft and coupler untreaded from back of engine. You will need to remove spark plug and feed a small piece of rope into a cylinder to stop the motor from turning over while you break the coupler free with a pipe wrench. the coupler is right hand thread. You can find a parts breakdown on line. Once you identify the coupler you will see that the repair is not too hard. Hardest part will be finding parts as Polaris parts are no longer made. You will also need new gaskets and orings as long as you have it apart replacing the impeller would not be a bad idea.

06-12-2014, 12:15 PM	#3
unixdood Junior Member Join Date: Jun 2014 Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	i can pull the engine or pump or whatever, Its not that im not mechanically inclined, just looking for a starting point as I have never experienced this before on any other jetski I have owned. I know there isnt a clutch or anything, so maybe your right that the impeller is slipping but still, that should be on a spline shouldnt it? Could it be the wear ring causing it? I didnt think so because the hole shot is fine so its got great pressure out the jet pump.

06-12-2014, 07:01 PM	#5
Winnaholic Junior Member Join Date: Apr 2012 Location: Seacoast Maine Posts: 6 Thanks: 14 Thanked 1 Time in 1 Post	I had that same problem on a Sea Doo GTX. I tried to figure it out like you and I'm mechanically inclined, turned out to be the impeller was spinning on the spline of the drive shaft. The teeth on the spline were worn and under acceleration the impeller would slip. What got me was there was no noise that you would expect like grinding, I finally got help with it from the boys at DeSilvas, ended up replacing the drive spline and impeller. This sounds like your situation, hope the info helps.

06-12-2014, 07:17 PM	#6
WeirsBeachBoater Senior Member Join Date: Apr 2004 Posts: 709 Blog Entries: 9 Thanks: 39 Thanked 148 Times in 65 Posts	Inspect your impeller, and the space between it and housing. Sounds like cavitation usually caused by damaged impeller. Polaris doesn't have a wear ring like seadoo.

06-13-2014, 06:02 AM	#8
unixdood Junior Member Join Date: Jun 2014 Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	thanks everyone for your input. I will be tearing down the impeller this weekend. Ill let you all know what the deal is when im done!