Anyone running a mag prop in a OEM SJ pump please provide feedback on performance changes.
I'm running a blueprinted OEM pump w/ 9/15 Hooker and need to upsize my prop. Was thinking of repitching to 11/17 or possibly going all the way up to 14/19. Engine change from ported 760 BB to SS 850 PV setup. Solas recommended the 11/17 but a few peeps on here with similar engine/hull setups have said they needed more prop than 11/17. I'm going to try a C-75 12/17 first before the repitch effort. Really need a mag pump but the wallet needs a break.
As an aside, are you guys sealing your pump gasket to the pump shoe with any silicone. I did that on my first few builds and hate doing it now since I pull the pump more often and its a biatch to strip all that silicone every time I pull it.
If you are repitching your Hooker impeller, then you should work with dave at impros to find the correct pitch. He designs the impellers and should be able to help you best.
TBM cones in combination with big hub impellers will provide you with a 'poor man's MAG pump.' I used to run that setup with my XS865. They will hook up better than a stock pump, but are
NO substitute for a MAG pump. The TBM setup still leaves you with a bighubbed oem pump with long thick cast aluminum vanes. The MAG pump usually has 12 vanes that are much shorter and much thinner stainless steel. Additionally, the center hub is smooth without the joints found all over the TBM.
OEM 144mm Yamaha pump vane section was designed in 1990 when Yamaha introduced their 'powerhouse' 650 motor in the superjet and WR3. It was never changed or improved when they introduced the 61x 701 motor in 1994 or the 62t/61x motor in 1996.
In 2008, yamaha redesigned the SJ hull bottom for better hookup by changing the pump intake area and by lengthening the driveshaft and moving the whole pump back by 2". This setback of the whole pump is not be confused with the setback stator vanes within the Mag pump, see below. This improved hookup but still didn't change the original pump design. While it is super impressive that the oem pump designed for an anemic 650 will still work for with a ported 701/760 with a bpipe/etc. It also isn't an optimal setup for performance.
MAG pumps have bigger hubs to increase the pressure and the power of the thrust out of and through the pump. They also have more veins which are redesigned and thinner (stainless vs cast aluminum) so they straighten the water flow better. They also will produce thrust even with less than optimal water flow, which is most of the time when you are riding. Another big difference that I notice is how quickly the MAG pump will rehookup when you land. When you ride in choppy water, it is amazing the difference.
The setback MAG pump requires a custom setback driveshaft. The pump stator veins are moved back (setback) closer to the reduction nozzle. This leaves room for more water in front of the pump for longer hookup. I have never compared the differences directly to be able to comment on the difference from actual testing.
As far as sealing the pump to the shoe, I prefer to align the pump/wear ring and seal it up well. Whenever you remove the pump after that, leave the wear ring sealed and aligned in place, just remove the pump/driveshaft for impeller swaps.
