Harley powered twin jet drive problem

Hi all, I just bought a jet boat.... built on a 13' airboat hull with twin jet drive powered by a Harley Davidson motor. The previous owner (not the builder) broke the carrier bearing mount on one side. The motor drives 2 chains that drive the two jet drives one on each side... motor in the middle.... the gear on the side that mount broke just spins on the jet shaft.
The gear is not held stationary with a set screw or any other mechanically means. Looking at the other side that gear looks like it's held stationary by some material like silicone to the shaft drive. I find it hard to believe that would hold up..... but I dunno... any experienced builders have any idea?

 

Hmmmm...
Do you have any pictures?

 

Welcome to the Forum Eddy.
It is difficult to try to picture the propulsion set up based on your description above - I will endorse Bluebell's request for some photos, as I am sure that they will help a lot to explain what is going on.

 

Here's s the pic of the chain drive, small gear is on jet drive shaft

 

The old operator tried to shift motor while underway, against the advise of builder. That broke the base of the carryer bearing and must of produced enough torque to spin the gear on the jet shaft.
The small gear on the good side has a whiteish material around the shaft that is soft in nature.... adhearing the gear to the shaft. It is flexible when poked with a sharp abject. the bad side has no weld marks or set screws, or grooves in the jet shaft or in gear that would show how it is fix to shaft.... just a little flexible residue, like a silicone sealant.

 

most likely a sheared key.
You cannot see underneath the sprocket hub.
Obviously, before this was converted, the jet input shaft required a keyway to transmit the torque to whatever it was hook up to

 

I have spun the shaft and the gear.... there is no keyway where the gear is. I agree that before converted I would think the end of shaft would of been splined or keyway. I will go out and look tomorrow in case he put a halfmoon key way in and the gear sheared the key flush with shaft and I didn't noticed it

 

I would suspect that it is a sheared key. Half moon (woodruff) or square.
What type of pumps are they? If you find out, you could go on line looking for parts and check to see if there is a key in the original shaft

 

I got the gear off.... no keyway, in gear or shaft... gear is a (50BTB12 1008) It was very sloppy on shaft, it looks like a set screw comes in from the side expanding a bushing, gear is missing the set screw. 2 of the 3 holes are filled with silicone.
link of a new gear.... asisurplus.com/martin-50btb12-1008-bushed-sprocket-50-12t/
Ive never seen anything like that.....

 

Are you going to do the other one at the same time?

 

Ditto here. It appears that the previous guys thought was that the silicone would hold the spreading screws from backing out or just hiding that some were not there
I would put NEW screws back in with red loctite and change the pulley and expansion collar out completely. If the set screws have been shaking around loose and under some load between the inner expansion collar and the outer gear, more than likely that something has worn. And just putting even new screws back in may never tighten and last a long time.(depending on what has worn)
When you take one of the screws out, check for a taper in the threads, ie top to bottom. Perhaps the set screw is proprietory to the manufacturer and tapered to suit both the gear and the inside expanding collar and a normal one might not work. (even if the threads may catch)

 

The other side appears to be working fine... here's what I found out about tapered bushing.
( Taper lock bushes are used for mechanical joining of a shaft to a sprocket or a pulley.. They are effective in high torque applications due to their evenly spaced installation)

 

Yes I think that's a good idea.... it appears that sprocket has been spinning a bit.... I'm shopping for new bushings

 

When you first showed the gear off the shaft, I thought that the set screws were being used to compress the internal ring onto the shaft.
I queried the location of the two set screws closest the slot in the internal ring.
The internal ring and the external sprocket hub bores are tapered and the set screws pull the inner tapered ring into the tapered bore sprocket hub to lock onto the shaft by friction alone.
Your picture shows quite a bit of internal bore wear/scratches. If the jet pump shaft is also scratched up, I would be sceptical of the surfaces providing enough friction to carry the torque.