300/440/550 650 in a 550

[kevbo]

Dude you are wrong on this I don't know where you are getting your knowledge from but I call bullshat, it is kind of like saying It's not going to be as good as a Mag pump??? Crashnburn do some reading on this topic over on PWC just because they have a good vintage section. There is alot of history there on this very topic. This Mod is old school and it is one of the best thing's that ever happened to the 550 hull. Don't even consider a 440 pump or a 550 powerplant on a build that you are not commited to yet. If you already had a good motor ready to drop in then fine go with a 550 and enjoy yourself but it sound's to me like you have a hull and are trying to build a ski. Do some research let me know if I can help you.

A 550 pump may work well enough, depending on your standards.
I get my knowledge by measuring thrust. A 750 engine can make enough power to produce 600+ pounds of thrust with a 140mm kawasaki or 144mm yamaha pump. I realize that this modification is not realistic for most people, though it is required for maximum acceleration.

 

[Motorheads5]

Nobody said anything about a 750 engine. The kid is trying to find out what other's have done and experienced. What have your expariences been with the conversion what pipe have you ran and what pitch prop ect.

 

[Kalwren]

I agree.

I have been piecing together a 650 conversion ski for quite some time. It's a ton of fun. Mine is done enough to be riding on it.

My girlfriend also bought a 650 conversion ski, so we're rocking two of these.

I have a 550 pump. She has a 440 pump. You can use either pump. I prefer my 550 pump though. The 440 can be a better pump with the right setup, but if you don't have a good impeller pushing it, it won't be fun to ride.

If you have a 550 pump already, then drop the 650 engine in there and enjoy it. There's lots of mods you can do it, too.

On my ski with the 550 pump, I'm running an 18 degree impeller. On my GF's ski with the 440 pump, she's using a 14/16, I believe. The 440 pump with such a low prop is NOT fun, as it takes about 3 seconds for the impeller to load the pump with pressure before it starts moving. Once it starts though, it's jammin and it's fun.

With my 550 pump, I don't have that problem. It hits hard and fast out of the hole.

Good luck! Let us know how it comes out!

do the 550/650 conversion... its the best thing that could happen to you and the 440/550 hull

I run a 17p prop on mine and did not have any cavitation problems

I have read up about this quite a bit and th 550 pump is the better pump for this application

 

[jetskijockey]

I agree.

I have been piecing together a 650 conversion ski for quite some time. It's a ton of fun. Mine is done enough to be riding on it.

My girlfriend also bought a 650 conversion ski, so we're rocking two of these.

I have a 550 pump. She has a 440 pump. You can use either pump. I prefer my 550 pump though. The 440 can be a better pump with the right setup, but if you don't have a good impeller pushing it, it won't be fun to ride.

If you have a 550 pump already, then drop the 650 engine in there and enjoy it. There's lots of mods you can do it, too.

On my ski with the 550 pump, I'm running an 18 degree impeller. On my GF's ski with the 440 pump, she's using a 14/16, I believe. The 440 pump with such a low prop is NOT fun, as it takes about 3 seconds for the impeller to load the pump with pressure before it starts moving. Once it starts though, it's jammin and it's fun.

With my 550 pump, I don't have that problem. It hits hard and fast out of the hole.

Good luck! Let us know how it comes out!

I should say though that I was running a ocean pro reduction and steering nozzle. Your 18p prop is probably perfect for the conversion...

installing a reduction nozzle is like installing a higher pitch prop

A 650 motor does not produce the revs like the 440/550 motors do. The 650 is much more torquey which the 550 pump benefits the most.

The 440 pump is a better pump for engines with a higher rpm/power band

 

[Kalwren]

A 650 motor does not produce the revs like the 440/550 motors do. The 650 is much more torquey which the 550 pump benefits the most.

The 440 pump is a better pump for engines with a higher rpm/power band

From my experience, this is correct. You really need high RPM engine to push a 440 pump and a nice steep impeller. The 650's don't have high RPM, but they have a lot of torque. They also get crazy good gas mileage.

 

[crashnburn86]

alright alright ill do a 650 in it! now someone lead me on to a good 650 out there i can buy... along with all the stuff i need to do the conversion

 

[jetskijockey]

Yes, you cannot be the gas milage and reliablity. I found that the biggest pain is the loudness...

I am fixing this with a a coffmans resonater added after the waterbox...

the stock pipe (mod) works well with the 550/650 setup

 

[jetskijockey]

alright alright ill do a 650 in it! now someone lead me on to a good 650 out there i can buy... along with all the stuff i need to do the conversion

buy a 650 with good compression and swap in new crank seals right away...

you are going to need a 650 voltage regulator

 

[madscientist]

pm me for details on a motor. i have at least 1 for sale

 

[jetski9010]

I got a built 650 motor. Has 44 SBN carb, shaved head, .050 squish, 180 psi, Rec porting, E box, westcoast pipe. Let me know if your interested.

 

[john zigler]

i have a very nice, freshwater 650 short block, 300.00. also have exh manifolds, and pipes ( stock), SBN44's and intakes, performance reeds, conversion plates, etc.

if you purchase from me, i would be happy to help with tunning, and set up. you can get a 650 to run pretty good, with some easy, cheap mods.

zig

 

[john zigler]

A 550 pump may work well enough, depending on your standards.
I get my knowledge by measuring thrust. A 750 engine can make enough power to produce 600+ pounds of thrust with a 140mm kawasaki or 144mm yamaha pump. I realize that this modification is not realistic for most people, though it is required for maximum acceleration.

i had a full mod, race gas 750 motor in a 89 550, back in the day ( mid 90's). blue printed 550 pump, with scat 19 prop. no cavatation issues. hooked up, and worked well for what it was.

 

[Kalwren]

Loud? Odd. Mine isn't loud at all. I'm running a stock exhaust though, with the pipe dragging around in the water. My GF's ski is running without the exhaust in the water, it's straight out the water box. Hers isn't loud either.

Not sure why yours is.

Yes, you cannot be the gas milage and reliablity. I found that the biggest pain is the loudness...

I am fixing this with a a coffmans resonater added after the waterbox...

the stock pipe (mod) works well with the 550/650 setup

 

[jetskijockey]

Its loud because of the stock pipe mod and the FPP water box.

I now might purchasing a 550 that has a SJ adapter hull that was built by Sano

 

[Kalwren]

I now might purchasing a 550 that has a SJ adapter hull that was built by Sano

I'm lost... what do you mean by purchasing a 550 that has a SJ adapter hull?

I have no idea what that means, lol.

 

[jetskijockey]

Its basically a 550 topdeck with a SJ bottom... I do not know too much more about it. waiting for some pics and info.

 

[Motorheads5]

Interesting I would like to see that. The claim to fame about the FX-1 was to beat out the 550/650 conversion ski's except being a production model, haha Yamaha really had something too except for the pump.

 

[jetskijockey]

Interesting I would like to see that. The claim to fame about the FX-1 was to beat out the 550/650 conversion ski's except being a production model, haha Yamaha really had something too except for the pump.

I will post some pics of it when I get it... (pretty sure I will)