300/440/550 650 Conversion ski - 440 pump & impeller

[Kalwren]

I'm probably opening a can of worms with this, as I know this can be a hot topic... I'm looking for information on using a 440 pump in a 550 hull on a 650 engine.

I think it's a 16 degree impeller that is currently in it and I don't like the way it performs. It takes to long to build pressure in the pump before you start moving. It has no "out of the hole" or "hole shot" take off.

Once you get moving, you're fine. As long as you stay moving. If you drop the RPM to much the pump looses pressure and you slow down and it takes it a few seconds to build back up.

I want to stay with the 440 pump.

I'm wondering what I can do to improve the performance. Different impeller? If so, what degree?

Will just changing the impeller fix the pump pressure problem or do I need to do other things?

Thanks in advance.

If you could point me to additional topics on this, that'd be great.

 

[tymeshare]

How deep are you going in mod'n the 650?..

If you are keeping it stock..

Look at a 17* impeller..and better grate to keep it loaded..

If you mod it out..

Well..I've never had one with that much power..lol

But you"ll be looking at "banzi" mod, taper bored cone, scoop grate..

 

[Kalwren]

The motor is stock. It has a Mikuni 44SBN on it though. Other than that - no mods really.

I think it has a 16 on it. Will a 17 really take care of that problem?

 

[WFO Speedracer]

Do yourself a favor and ditch the 440 pump, I floundered around with one for over a year in my 300SX conversion ski, no matter what prop you put in it you will never get any holeshot out of it. The 440 pump is designed for rpms and flow,440's and 550's used to twist 10,000 rpm or more in the race boats, wih the 650 engine you need a bigger pump or at least a 550 pump that is more suited to the lower rps that engine produces.If you could find a Skat four blade 440 prop you might get it to work ok but it still will not hold a candle to a 550 pump.I sold my last four blade to Yosh over at PWCT.

 

[jetski9010]

The 440 pump is going to do that more then a 550 pump would. I would swap over to a 550 pump if I were you. If you going to stick with a 440 pump bore the nozzle as much as you can get a 17 or even a 17.5 prop and a top loader intake grate. Your not going to get good low end pull with that 440 pump.

 

[WFO Speedracer]

I cut the 440 pump tunnel out and trashed it, grafted in a 650 pump tunnel , installed the 650 pump, shaft and bearing setup along with a 650 motor , problem solved.

 

[Kalwren]

Awesome guys, thanks for the replies.

I'm trying to sell this idea to the person who has the ski...lol. I've been saying get a 550 pump but she's not interested.

We'll see how round #2 goes. I figured it was the RPM issue of the 650 engine.

Anyone else have any input to this?

Thanks again!

 

[jetski9010]

go with the 550 pump. Get the nozzle bored, freestyle cone, and a 13-16 prop with a good top loader grate and it will hook up and hit good. thats the setup I am running on a built up 550 motor and it hits good.