second broken midshaft-driveshaft

jkirkland

jkirkland

jkirkland
Location
inverness florida
This is the second time I have broken a midshaft-driveshaft in my blaster. Does anyone make a better or stronger set up? Are any of the other yamaha ski's that use the same set up? What do you guys with the really fast blasters do to keep this from happening? Thanks for any help--Jason--
 
Freakrider

Freakrider

X247
Location
Tampa Bay area
I know of one theory out there as to why blasters strip driveshafts so often or in your case break it (they get hot as a mofo)...the bulkhead is misaligned in the hull on many blasters causing the midshaft to be out of alignment...monitor midshaft heat and alignment for sure...
 
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tshank123

tshank123

Yo hablo ingles
Location
Vegas
If its misaligned then you should be able to shim it to compensate. There's no reason you should be going through midshafts and driveshafts if everything is lined up correctly.
 
tom21

tom21

havin fun
Location
clearwater FL
bingo, and fyi jetmaniac is selling modded couch driveshafts. maybe he has a beefier part for you. you will still need to align it or it will damage that one also.
 
R

RoTAxGreNade

X-
Location
Port St. Loozer
Pull the mid-shaft bearing carrier and make sure the pump is aligned - the prop shaft should be centered in the hole with the pump bolted up. (You may be surprised how many shims under the pump ears you may need).
Then slide the bearing carrier/mid shaft assy on and it now should line up with the locating dowel, 3 bolt holes and be near flush and square with the bulkhead as possible (they also have shims for that too). The goal is to seat the bearing housing with the bulkhead with minimum deflection force put on the floating bearing housing when it's time to torque everything up.
THEN align your motor/couplers without the do-nut - I think the tolerance is like 1 or 2 mm but have seen many get away with much more.
The first 2 alignments are more critical to shaft life than the coupler alignment in my experience. Stricky, and Jason went thru 3 shaft sets before we figured out the problem.
 
jays333

jays333

Location
Australia
yeh a;;ign it properly i go through about 2 sets a year cant be helped cav slides and mid air revs are no good for blasters ,welded my first blaster driveshafts together lasted as long as the prop a little bodgie but worked at the time
 
R

RoTAxGreNade

X-
Location
Port St. Loozer
Jays - Bet you didn't replace the 2 o-rings inside the mid shaft AND use moly grease on the splines......
You have to use MOLY grease NOT your waterproof bearing grease - moly is an extreme pressure and load bearing grease but is not waterproof hence the importance of the o rings in the shaft.

I have only replaced one shaft set in mine many years ago - I am 210 lbs and have to land with the power on and that's as brutal as it gets on the driveline.
 
Freakrider

Freakrider

X247
Location
Tampa Bay area
Because the bulkhead is misaligned in the hull on many blasters, the driveshaft is off center left or right and the only fix is to wallow out the holes in the reduction nozzle to shift the pump a bit left or right...
 
R

RoTAxGreNade

X-
Location
Port St. Loozer
It's the sloppy tolerance on the pump mounting surface during production that is the main problem, not the bulkhead being misaligned and 90% of the time the shaft sits too low in the bulkhead hole hence the factory shims being on the rear mounting ears only.
Once you line up your pump/prop shaft with the hole and slide the mid housing on the shaft and seat it lightly to the bulkhead is when you will see if the bulkhead is off square - You should not have to pry or force the housing to get the dowl to go in the hole or start the 3 bolts. How easily your pump slides in and out of the mid housing with the engine disconnected is kind of an indication of how far things are out of whack.

Waste of time drilling out the ears as there are locating dowels on the tabs anyways - it's very rare the shaft will be that far off from left to right in the hole and you can shim some of that out also.
 
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