Hi, this is my 1990 550sx/650 conversion. The 1990 hull has been in use for only 1 season(the guy who had it managed to fry the motor in 10 hours of use) and spent 20 years under a tree, but other than the paint it was in exceptional condition(no stress cracks at all). So, i built a new 650 motor for it(hot rod con-rods, sudco cast pistons, ported the cases and polished the exhaust ports, mariner head, ported exhaust manifold etc. Currently running 200psi in both holes). After a lot of work trying to fit everything in the 550sx hull and changing every little bit of the ski with a new one, the result was really good. I also installed a westcoast waterbox, a solas straight 17 pitch prop and a wetwolf pump cone. I think that the only downside with these skis is the small pump, but i am gathering all the parts now and already have a 650sx hull i would gladly chop to take the pump tunnel.
300/440/550 My 650 conversion
- Thread starter papadon
- Start date
N2 H2O
Previously Tbone550
- Location
- Charlotte, NC
Cool ski. Do you have any gps numbers on it? My 650 conversion is closing in on 50mph
It tops at 40-42mph, but the 17p prop is not too steep at all for this setup. I will try to find a 19p prop(i can't find parts in my country, so i always buy parts from the US), but these things are just not for sale. If i don't find a prop, i will install my 650 pump to the ski. I have seen your conversion ski and it seems really cool. Did you notice any change in power/throttle responce with the 750 cases? I think that they have bigger volume, so that should work good for air/fuel velocity in the motor. Also, i am trying to find a dual manifold for the 650 motor which could fit the 550sx hull, as my 38mm keihin is really really small for my motor. It runs really strong on bottom and mid end, but on the top end you can see that the motor really needs a much bigger carb, or even two of them. Do you have anything in mind?
N2 H2O
Previously Tbone550
- Location
- Charlotte, NC
a sbn46 would be pretty good with your setup. I currently have a sbn44, but plan on upgrading this winter to a 46. The 750 cases definitely made a difference. Th intake ports are a good bit larger on them, which I think helped a lot. Impros will repitch your prop for a very reasonable price. Most of the conversion ski guys just send a prop and get it repitched to what they want.
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
BTW I have a 650 pump tunnel I pulled out of my X2 for sale cheap if you want it.
N2 H2O
Previously Tbone550
- Location
- Charlotte, NC
Well a 46 is bigger, which = more air and fuel, which = more power. The biggest difference would be that the 46 would give more top end. I have a complete sbn44 carb setup for a 650 for sale(intake mani, carb, f/a adapter, and a ton of f/a's to choose from)
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