Need help! Engine wont turn RPMS, think problem is in pump

[RUNWME]

What happens is when riding down the river at 1/4 throttle, your turning 4500 rpm. If you mash to full throttle, the engine changes tone as it loads, but rpms wont increase.
Its like the Dominator Jet Pump is acting as a dyno waterbrake and binding up not letting the engine turn up.
This 468 chevy engine has hydraulic roller cam, tunnel ram and built by very respecatble engine builder. I really doubt its a power issue.
I am not familiar with jetdrives... any ideas?
[ June 25, 2003, 09:53 AM: Message edited by: RUNWME ]

[dgie]

it sounds familiar to the problem that I am having, you might want to check the size of the impeller I am going to do the same on mine. I called the jet manufacturer of mine (Jacuzzi) they said more then likely thats the problem. If it is too big it could hold the rpms down, and not move enough water.

[RUNWME]

It now has a dominator pump. He has a berkley pump with a electic motor attached to it. I know this sounds like an idiot question Should I try the berkley pump?
David
[ June 25, 2003, 07:28 AM: Message edited by: RUNWME ]

[Moneypitt]

1/4 throttle is 4500 rpm!!! what kind of rpm will it rev on the trailer, 18,000?? I realize the problem is increasing the rpm from 1/4 throttle, but I question the tach. In fact the tach COULD limit the rpm s if it has an internal problem. What kind of rpm do you expect if everything is right? Unless a jet has extreme mods, they really won't rev much over 5-6000 max, regardless of the engines limit, the power required to gain only 100 rpm past normal is straight up on a hp graph....Moneypitt

[Taylor LP]

Is this a for real post???????? Electric motor????
Maybe he has way to much cam.

[BK]

Taylor LP:
Is this a for real post???????? Electric motor????
Maybe he has way to much cam. Probley talking about the place diverter/jetovator motor.
You say your at 4500 rpm and when you give it more gas the motor does nothing? Does it get on plane easily? Or do you have to baby it up onto plane? What kinda ignition is he running? Is there a rev limmiter?
[ June 24, 2003, 01:02 PM: Message edited by: BK ]

[superdave013]

Lube your bearing buddies and you'll be all set. :)

[RUNWME]

Agian I am new with jetboats, but not new with boats or engines. I raced Super Comp and brackets for years.
The tach could be off but it seems relative to engine rpm. It jumps on plane fairly strong (as good or better then my STV with 245 bridgeport)
Yes 4500 at 1/4 throttle, that is why I was thinking it should have more. I would have at least expected a 500 rpm differene between 1/4 and wot. The boat isnt moving very fast. Speedometer reads 74 but GPS only puts it at 64 (it is a 1978 Hondo picklefork) And no ,get real money pitt, it won't turn 18k rpms on the trailer, it maxes out at 17,500 on the trailer(hehe)
I will pull the plugs after next hard run, it is possible the carbs are leaning out on the secondary side hence increasing noise, but not power.
Just wondering if the pump could be maxing out and not allowing the motor to turn it past 4500rpm.
Agian, forgive my ignorance, I am a jetboat newbie.
BTW the electric motor trims the nozzle. He did call it a diverter. It is brand new Berkley unit never mounted, think it would be faster then the Dominator jetpump?
AND Lastly! Welcome me to the JETBOAT community, I just purchased the boat few minutes ago when owner said "David, I am thinking about selling it..."

[superdave013]

OK, really it sounds like your engine does not have enough oats to spin the impeller that's in the pump.

[572Daytona]

Welcome to the jetboat community! I'm tempted to ask where the motor was dyno'ed but I won't go there in this thread wink If you aren't turning the rpms usually it is not a problem with the pump. Someone pointed me to this web page a while back and I find it a does a real good job of explaining where the problem may be:
http://www.outlawmarinejets.com/understand.htm

[565edge]

Is it a jet hydro?

[RUNWME]

565edge:
Is it a jet hydro? I should have used the KISS method of diagnostics!!
K-I-S-S Keep it simple stupid
The throttle linkage angles were incorrect. It was only opening carbs up approx 1/2 way when mashing throttle.
Should have checked that first. I appreciate everyones suggestions. Turning over 5k RPMS now and feeling much stronger!
The boat is 1978 Hondo Picklefork.
I tried talking my wife into letting me get it but we already have a Hydrostream Voyager and STV in the shed.
The boat will be posted for sale after July 4th (she said I could run it for a few weekends!! )
Not sure how to post pics.. but here is a site where you can see it.
http://www.tarriversports.com/boats.htm
http://www.tarriversports.com/boats.htm

[Hotcrusader76]

Are you sure that you're getting full throttle opening? I assume you checked the pedal/throttle operation?
~Ty

[RUNWME]

I had my wife climb into it and mash the go pedal while I looked down the carb bores. After resetting linkage the butterflies are going wide open now. Before when it was only turning 4500 the butterflies only open 1/2

[dgie]

man that sucks, you fixed the problem now you have to get rid of it,,,,thats just wrong