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Supercharger volute pinning, 2013 through 2017 Yamaha SVHO engine
Update note: For 2018 Yamaha revised the SVHO supercharger, and my understanding is that the volute no longer requires pinning.
Volute pinning does apply to SVHO superchargers made in 2013 through 2017.
Here are my notes on pinning the volute in the Yamaha GP1800 SVHO supercharger.
The reasoning behind this work is to avoid the potential of the volute moving within the supercharger housing and damaging the blades of the supercharger wheel. The risk of volute related failure rises with increased RPM (over stock) and increased boost levels (over stock).
It is unclear (to me) whether accumulating engine hours also increases the risk, but it seems reasonable that it might.
Installing a 'set screw' through the wall of the volute pins it in place so the volute cannot shift. I am not running high RPM or high boost, but I feel better knowing the pinned volute is never going to cause a problem.
Original thread is Attention: Owners of 2013 and newer Yamaha SHO/SVHO skis please read!!!
This is what the supercharger on the Yamaha (GP1800) SVHO engine looks like from the factory.
Reminder why this modification is worth doing. The front portion of the supercharger is manufactured using two pieces, which are then precision pressed together. The smooth vortex shaped volute inside is positioned very close to the spinning supercharger wheel. The front outer housing is bolted to the rest of the supercharger.
On superchargers manufactured after 2012, the only thing holding the inner volute in position is friction with the outer housing, where the inner sleeve passes through the front of the housing. For 2012 and prior years Yamaha manufactured these superchargers with a small screw in a hole bored through both layers of metal. This prevents the inner sleeve from shifting position relative to the outer housing.
You will be removing both of the large curved hoses connecting the supercharger to the air intake box (mounted on the left side of hull) and the intercooler (mounted to the right of supercharger).
Tip: If you are also installing an aftermarket air intake, now would be the time to disassemble and remove the stock airbox. It must be disassembled to get it out of the hull. With the stock airbox removed there is a lot more elbow room around the front of the engine. I even removed the airbox mounting bracket. I did reinstall the factory nuts onto the sidewall studs, just in case I ever want to mount something there in the future.
Remove both curved hoses.
Tip: Take photos and make notes of what came from where, and what order the parts were removed. Note how far the rubber hoses were onto the fittings, and how the hose clamps were oriented.
This is the first metal part to be removed. It holds the intercooler to the engine, but this bracket is in the way for access to the supercharger bolts.
Use an open ended wrench where clearances are tight. There is just enough room to get the bolt loose and wiggle the bracket away from the engine.
Remove two bolts to the intercooler, two bolts to the engine.
14mm bolt heads.
I used 14mm socket and 6” extension with long handled ratchet wrench to break them free, then a shorter handled ratchet to wind the sideways facing bolts out.
For the two forward facing bolts I use a box end 14mm wrench to crack them free, wind them most of the way out using ratchet type box end stubby wrench.
Then use an open ended 14mm wrench for the last few turns as a box end wrench would become trapped by the supercharger housing.
Don’t drop any bolts or washers
Volute pinning does apply to SVHO superchargers made in 2013 through 2017.
Here are my notes on pinning the volute in the Yamaha GP1800 SVHO supercharger.
The reasoning behind this work is to avoid the potential of the volute moving within the supercharger housing and damaging the blades of the supercharger wheel. The risk of volute related failure rises with increased RPM (over stock) and increased boost levels (over stock).
It is unclear (to me) whether accumulating engine hours also increases the risk, but it seems reasonable that it might.
Installing a 'set screw' through the wall of the volute pins it in place so the volute cannot shift. I am not running high RPM or high boost, but I feel better knowing the pinned volute is never going to cause a problem.
Original thread is Attention: Owners of 2013 and newer Yamaha SHO/SVHO skis please read!!!
This is what the supercharger on the Yamaha (GP1800) SVHO engine looks like from the factory.
Reminder why this modification is worth doing. The front portion of the supercharger is manufactured using two pieces, which are then precision pressed together. The smooth vortex shaped volute inside is positioned very close to the spinning supercharger wheel. The front outer housing is bolted to the rest of the supercharger.
On superchargers manufactured after 2012, the only thing holding the inner volute in position is friction with the outer housing, where the inner sleeve passes through the front of the housing. For 2012 and prior years Yamaha manufactured these superchargers with a small screw in a hole bored through both layers of metal. This prevents the inner sleeve from shifting position relative to the outer housing.
You will be removing both of the large curved hoses connecting the supercharger to the air intake box (mounted on the left side of hull) and the intercooler (mounted to the right of supercharger).
Tip: If you are also installing an aftermarket air intake, now would be the time to disassemble and remove the stock airbox. It must be disassembled to get it out of the hull. With the stock airbox removed there is a lot more elbow room around the front of the engine. I even removed the airbox mounting bracket. I did reinstall the factory nuts onto the sidewall studs, just in case I ever want to mount something there in the future.
Remove both curved hoses.
Tip: Take photos and make notes of what came from where, and what order the parts were removed. Note how far the rubber hoses were onto the fittings, and how the hose clamps were oriented.
This is the first metal part to be removed. It holds the intercooler to the engine, but this bracket is in the way for access to the supercharger bolts.
Use an open ended wrench where clearances are tight. There is just enough room to get the bolt loose and wiggle the bracket away from the engine.
Remove two bolts to the intercooler, two bolts to the engine.
14mm bolt heads.
I used 14mm socket and 6” extension with long handled ratchet wrench to break them free, then a shorter handled ratchet to wind the sideways facing bolts out.
For the two forward facing bolts I use a box end 14mm wrench to crack them free, wind them most of the way out using ratchet type box end stubby wrench.
Then use an open ended 14mm wrench for the last few turns as a box end wrench would become trapped by the supercharger housing.
Don’t drop any bolts or washers
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