300/440/550 1990 550 sx pump question

[spug]

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I just got my first 550sx, since the 10th grade, for the wife. It's got a PJS pipe, Jet Sport head and skat-trak prop and few other things. Do you know what the deal is with the pumps on these things? It slips like crazy. All the tollerances are tight in the prop area and everything is sealed. Is it just because it is so small? What mods and props are people using to get these things to hook up? I've been a Super Jet guy for a long time and have been out of the 550 loop. Thanks all.

-Brad

 

[special fx]

Make sure no one silconed in the the gaps between the ride plate to pump shoe. Don't know why exactly, but this will make a 440/550 cavitate like mad.

 

[spug]

That is kinda' weird. There was no silicone there but the pump shoe is sealed nicely to the hull itself.

 

[Motorheads5]

could it be way over propped what pitch are you running?

 

[spug]

I just found out it's a Skat-Trak 4-7 which I guess is a 14-17 variable pitch. Too much? I've been doing a little reading tonight and it seems a 15 is the way to go. Is shimming the prop to the housing important? I checked it out before I pulled it out and it seemed to be slightly off center.

 

[Motorheads5]

I would think that 550 should pull a 14/17 ok. yes shimming the impeller is important you want it as close as you can get it without hitting, you said it was off center you might have a swollen liner in the pump housing and some wear issues to look at.

 

[jet750]

i would take the pump out and resilicone it and make sure there is no air gaps, also use silicone to glue the intake grate up too. If you have a toploader on that could be part of the problem too, i put a toploader on my ski and it would cavitate right off the holeshot.