SoCal Jet Boats
Tech Talk => Jet Pumps => Topic started by: ta69man on July 05, 2011, 10:48:11 AM
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Ok,
So I live on the other coast from this forum, but I hope things still work the same over here...
My father has had several jet boats in his life time and recently got an itch for another. I'm a gear head, but don't know jets... so here goes:
Dad got a '95 Ultra jet boat (18') with a 454 BBC and water injected Bassett headers. It has a Dominator pump and I'm unsure of the impeller. He got screwed on the deal as the interior was rotting under the vinyl, the motor was shot, and the pump was bad... but all of that is fixed now by a local boat shop that doesn't deal with jets...
We took the boat out this weekend and while it was fun... it lacked what I figured it to do. It was a dog out of the hole... I'm not sure it could pull up a skier (I think my pontoon would beat it to 20 mph) and the top speed was around 56mph (at un-known rpm, tach is dead, but I'd say nearly 5000 from the sound). The motor is running well and everything functions as it should outside of that. The boat just doesn't have any 'torque' and it slides up to speed. I expect the boat to be light weight as it has no floor boards or any 'extra' stuff and during our test we only had about 5 gals of gas in it.
Not having anything to compare it to I'm not sure if this sounds right... I have seadoo jet skis and they have way more torque... but I didn't know if something like that was comparable...
What aspect of the pump makes torque? And what contributes to speed? The motor would rev smoothly and I didn't notice any cavitation... The pump was rebuilt, but I wonder if they got the clearances wrong...
Thanks for your thoughts..
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When you say it slides up to speed, does that mean it takes it's sweet time getting on plane? Does the motor rev when you punch the gas, like a slipping clutch? I'm going to say that your problems lie in your pump. Might be worth sending it to Duane @ Hi Tech Performance (he's the closest to you that I can think of) for a good, solid rebuild.
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I consider myself a partial gear head and I have rebuilt a few pumps now. Not a big deal but you do need to get yourself a Seloc manual. It has the Dominator pump rebuild procedure in there. Also Duane is good people for parts/kits and the wear ring. You will need a couple of tools. Impeller puller and a deep socket for the impeller nut. Search the forum and you will see other people made a puller and also modified sockets. It does sound like the pump needs attention. It should pop out of the water and be on plane in less than a few seconds or so. Umm, well that's how my boat was anyway (more like fukin violent, almost breaking the seats).
Anyway, there is tons of material here, do some searching and I am sure there are rebuilds here too .
T.J.
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Thanks for the replies for far. I guess you could call the motor revving similar to a slipping clutch feeling.
My best analogy would be that the boat accelerates like a car going down a hill (without using gas pedal)... Yes you accelerate but you don't notice it much because there is little force pushing you back into the seat. Everything seems smooth... just without ummph like I would expect... Seeing that the guys that dad had work on this boat don't know jets (only deal with props) I expect that something is not setup correctly in the jet...
The next question is what to look for in the jet? I has all new parts so I'd think I just need to change some clearances.
Thanks
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IF there is nothing covering the intake or stuck in the pump one thought is it is sucking air and cavitating. I do not have experience with Dominator pumps but if I do not have packing adjusted right on my Berkeley it feels like a clutch slipping on a car. Internal clearances can have an affect but suggest you look at the simple things first. There are a lot of knowledgeable guys on the forum. You might do a search to see if there is a thread already.
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Call Tom at Jet Boat Performance he will be able to answer any questions you may have! jetboatperformance.com