300/440/550 440 to 550 or 650

jroberts#77

jroberts#77

Location
michigan
i just bought a 1991 js440 stand up jet ski. and i was wondering how indepth it was to do a 650 swap. i know that a 550 with just about bolt up. another question that i have is that would the extra hassle of the 650 swap be worth the extra power gain, or should i just do a simple 550 swap? any help would be helpful thanks jake
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
550sx Reed Motor would be easiest.

for the 650/750 swap you either have to use the adapter plate (Hard to find) or completely fab up mounting points yourself. (Not easy or fun).

Or, find a SN SJ or older Kawi 750sx
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
I would do a 750 over a 650. But that is a small hull.

I ran a 91 550sx that was set up as a limited race spec. If you are fairly light, then plenty of power.

If you have the means, then the bigger motor is better,
 
screaming440

screaming440

The Old Skool Professor
Location
KC/Lake of The Ozarks
you can get all the power you need out of the 440 if you do the right mods.

there is only a 25 hp difference between the 440 and 650 but there is a big weight difference. the 440 is so choked off that it is not that hard to get the horse power up to the 52 that the 650 has and the cost will probably be way less than the conversion.

the 750 mod is harder to do cuz it has a different ignition that is less compatable with the 440 /550.
 
caseville9036

caseville9036

BLRider
Location
SE MI
Where are you at in Michigan? There are a bunch of us here that have conversions that could answer some questions or possibly test ride.
 
N2 H2O

N2 H2O

Previously Tbone550
Location
Charlotte, NC
subhard said:
So does a 550 reed motor just drop in and hook up to a 550 PP hull? What about flywheel, stator, starter, intake, exhaust etc?
Click to expand...
The intake and carb is different, but everything else on the motor is the same. The pumps and driveshaft setups are also different and the sx hull has rear exhasut and the rubber tray sides.


I loved my conversion ski. I liked how it handled better with the extra weight in the nose also. It really helped it urn and handle better in rough water. I have most of the parts you would need to drop in.

550 reed motors also make good power if they're set up right. Either option can be made into a very fun ski.

Where and what kind of riding do you do mostly?
 
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fastgtfairlane

fastgtfairlane

Location
Charlotte, NC
the 550 reed engine with a full pipe will be a much better setup for the 440 pump than the 650 or 750.. the 550 reed will also be the cheapest and most cost effective bang for your buck.. if you go to a 650 or 750 engine, it will be wise to also change the pump to a 550 pump... also in my opinion a healthy 550 reed with good compression, tuning, pipe and good 440 pump setup (impeller, bored or ocean pro outlet nozzle) will make a fun ski that will run right with the 650 or 750 engine.. the 440 pump is better pump for higher revving engine that the 550 is...that is the setup i run and its a very fun, light ski. has good low, mid range and upper 40s top end which will make the ski squirrely at full speed.. get the reed engine, get compression to 180ish psi, 44mm sbn, a/m exhaust mani and pipe, waterbox, get the pump blueprinted with 15.5 or 16pitch impeller and ocean pro outlet nozzle and you will have a very fun ski.. that is how mine is setup and i even have a 91 440 hull.. also reed stuffers and reed spacers will help out as well
 
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jroberts#77

jroberts#77

Location
michigan
screaming440 said:
you can get all the power you need out of the 440 if you do the right mods.

there is only a 25 hp difference between the 440 and 650 but there is a big weight difference. the 440 is so choked off that it is not that hard to get the horse power up to the 52 that the 650 has and the cost will probably be way less than the conversion.

the 750 mod is harder to do cuz it has a different ignition that is less compatable with the 440 /550.
Click to expand...


well i already have a west coast pipe, and ride plate and i also have a new impeller. what else could i do to squeeze out power?
 
N2 H2O

N2 H2O

Previously Tbone550
Location
Charlotte, NC
jroberts#77 said:
well i already have a west coast pipe, and ride plate and i also have a new impeller. what else could i do to squeeze out power?
Click to expand...
You can get a sbn44 carb, get an aftermarket or milled stock head, lighten the flywheel, get it ported, and even go to total loss and much more. But, I would just get the sbn44, mill the stock head, lighten the flywheel, and make sure you have a good impeller.
 
jroberts#77

jroberts#77

Location
michigan
okay so im new to the whole jet ski thing. i dont know whats the latest and greatest i just got into this new hobby so whats the benifits of a sbn44 carb?
 
N2 H2O

N2 H2O

Previously Tbone550
Location
Charlotte, NC
440's come with a bn38, so the 44 is bigger. The sbn's also have a better square fuel pump design compared to the round pumps on the older ones. The sbn's have interchangeable jets also which makes tuning easier. The bigger carb will mainly give you more top end


Sent from my iPhone using Tapatalk
 
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caseville9036

caseville9036

BLRider
Location
SE MI
jroberts#77 said:
i live in milford michigan but ride all over white lake mostly. and yes that would be greatly helpful and appreciated
Click to expand...
I'm just North East of you in Davisburg (just North of Highland). I drive through Milford on my way to work (in Brighton) daily. We should meet up.
 
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