550sx pre build questions

[zachtrowe]

Picked up a sx hull. Originally wanted to do a 750 swap but I think it’s biting off a bit more than I can chew. Debating putting in a 550 motor. Couple questions, would a js motor bolt right in and work with an sx exhaust? Before I do that is there an “easy” motor swap that would be preferred over just doing a bolt in 550 motor? Thanks
Pics attached is what I’m working with

 

[WFO Speedracer]

Yes 550 exhaust are all the same bolt pattern , manifolds, pipes etc all work. A tigershark 640 engine is a fairly easy swap on a 550 and way more power.

 

[fastgtfairlane]

That's actually a js440 hull. I can tell it's a js because of the tray, and bulkhead bearing block instead of the sx bearing on the bulkhead like the 650,750 etc has. The 91 and newer js440s were rear exhaust. You can get an adapter bearing for the housing that uses the sx style driveshaft and pump if you can find one. If you go with a 650 or bigger engine, you should definitely consider at least a js550 pump over the 440 pump, if not swapping the pump to a 750 pump with a conversion kit.

 

[WFO Speedracer]

440 pumps run fairly well behind a mild 550 with the right impeller, anything bigger than a 550 you need a much bigger , better pump.

I believe a lot of guys with really hot 550's are using the 750 pump conversions on their skis. that adaptor bearing is higher than a cats a$$ , I know I sold one for good money a few years back.

 

[hornedogg79]

Js550 motor will work great with a bread box exhaust. Definitely keep your 440 pump. That was the preferred pump back then. 90 was the first year of sx hull and rear exhaust. The reed 550 motor came a year later. All 440s have that bulkhead bearing.

 

[zachtrowe]

After doing more research, Im thinking of the 650 or 750 swap. Looking for a donor 650ts 750 that i can take the guts out of for the build.
@fastgtfairlane will it make the conversion tougher being a 440 hull?

 

[hornedogg79]

Swapping the motor is easy. $95 conversion plate from watcon. $39 ebox mount. $85 for conversion coupler. Then everything bolts right up.
To swap to a 750 pump it gets pretty expensive If you don't already have the parts. You'll need a pump/impeller, X2 driveshaft, conversion mid bearing,,750sx intake grate, 550 to 750 pump conversion kit, ride plate.
650 is noticeably lighter and the stock pipe works great. That'd be my choice. The 750 pump, with the right prop, works great with 550 -750 motors. I raced against a guy who has 2 pump swapped skis. One with a 550sx motor, the other with a 750 motor. He prefers the 550 motor/750 pump setup. He was very hard to keep up with.
Rear exhaust 440 hulls like yours are great because you don't have to deal with the rail cap voids when you turf the tray.

 

[WFO Speedracer]

The only drawback to using the 440 hull is it requires a fairly expensive conversion thru hull bearing from RHass , other than that same , same.

Kawasaki 550 Conversion Bearing

www.rhaasproducts.com

 

[WFO Speedracer]

I will say this for whatever reason the 440's seemed to have better hulls than the 550's I say this because I have never seen a 440 split at the bondline , I have seen several 550's especially 86 models.