Upgrading 90-93 SN midshaft strength?

Y

yamijumpn

Location
54956
Through much reading I know that the 90-93 SN superjets have a weak rubber to housing/bearing area which makes them tear apart easily. I also read that you want to avoid these for any sort of builds. Problem is then what do guys do with SN skis from 90-93 with powerful builds? If the bolt pattern/threads change in the hull its basically a lost cause having the older SN skis?
I have to get my ski from the cabin nxt weekend to verify but I am pretty sure my ski is a 93 and on my last ride got some vibrations in the tray. I figure its the splines more than likely since nothing was caught in the pump upon inspection and winterizing. Just want to get some fresh parts in the ski before i hit the larger lakes w/ the big rollers!

Any advice on upgrades? Buy oem left over stock?
 
N

Norcaltrd

Location
Redding, CA
If your housing is thrashed buy a used/clean housing and fresh housing rebuild kit from Jetmaniac.
For a stronger midshaft order the cold fusion midshaft.
http://www.x-h2o.com/index.php?thre...new-used-yamaha-and-custom-build-parts.85372/
I placed my order yesterday lol.

Yes the bolt pattern changes, you cannot use a 94 and newer housing on a 90-93 and vice versa.
Reach your hand up in the intake grate and attempt to rotate the shaft in either direction.
If it freely rotates loosely even the slightest your splines are worn. If you can move it in and up and down or side to side motion then the housing is shot.
Usually it will also make a pretty loud and obvious noise when its running at idle out of the water. The noise will go away under power because the splines tighten up against each other under load, while at idle they rattle back and forth.

Only replace whats worn, if your driveshaft is in good condition then dont bother to replace it.
You wont know for sure what it is until you pull the engine & midshaft or prop & driveshaft to inspect the splines.

However if I were you I would make sure the vibrations were not a one time thing or something imagined.
 
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