What impeller for best performance

[Dezertracer812]

I am new to the site and have a question about my impeller. I have a 21' baker tunnel hull with a dominator pump, ride plate, droop snoot and place diverter. My motor is a 496 with about 550 hp. I just had joe at jp marine add a pre impeller and re build the pump. I believe it has a ab cut. I took the boat out this weekend and hit 6700 rpm and was only doing 60mph. I have to keep the motor at 4-5000 to even do 35/40 mph. This seems like too much stress on the motor. Im looking to drop rpms and increase top speed. Thanks for the help.

 

[AJDEAN955]

I am new to the site and have a question about my impeller. I have a 21' baker tunnel hull with a dominator pump, ride plate, droop snoot and place diverter. My motor is a 496 with about 550 hp. I just had joe at jp marine add a pre impeller and re build the pump. I believe it has a ab cut. I took the boat out this weekend and hit 6700 rpm and was only doing 60mph. I have to keep the motor at 4-5000 to even do 35/40 mph. This seems like too much stress on the motor. Im looking to drop rpms and increase top speed. Thanks for the help.

maybe a big A or AA depending on how heavy your boat is sounds like your motor is over powering the pump you want to always have your pump set up to push the pump never over rev it, beacuse then your just waisting horsepower if you get a good ss impeller that is set up to run...say 6800 and your motor runs at 6700 you should be ok that way the motor is always pushing the pump never running faster than it!

 

[lf2]

Something else is going on a AB at 6700rpms would be way over 60mph. Is your tach correct?

To know what impellar would be correct you need to know where the motor made peak horsepower.

 

[cruzer]

How did it run before the "Rebuild"?

 

[Dezertracer812]

I spoke with the engine builder today and he said I need to have the max rmps be 5500/5800. The boat previously had a mercruizer 454 that also had high rpms and slow speed. max I have seen the boat do is 60mph and seeing almost 7000 on the tach is worrying me, thats how I blew the last motor but not 100% sure.im going to buy a new tach to see if the rpms are correct. Im thinking with 550hp i should do 70mph easily.

 

[Outlaw]

Is it still attached to the trailer???

Just Kidding

Has this guy ever built a jet pump before? Something is way wrong
Can you get some pics of the boat, pump and hardware??


Sent from my iPhone

 

[jetboatperformance]

I am new to the site and have a question about my impeller. I have a 21' baker tunnel hull with a dominator pump, ride plate, droop snoot and place diverter. My motor is a 496 with about 550 hp. I just had joe at jp marine add a pre impeller and re build the pump. I believe it has a ab cut. I took the boat out this weekend and hit 6700 rpm and was only doing 60mph. I have to keep the motor at 4-5000 to even do 35/40 mph. This seems like too much stress on the motor. Im looking to drop rpms and increase top speed. Thanks for the help.

Sorry to be a downer but assuming your Tach is correct something is seriously wrong here , with due respect to those involved (depending on where exactly your motor makes its 550 hp ) it should spin an ab around 5400 rpm max and add to it the inducer maybe a smidge less(WOT) . in a tunnel hull you should have an "economy cruise" of around 3200/3500 rpms 30-35 "ish" mph. We would have started you with an AA and worked down if the need was there . Please feel free to call for more info , Happy to help diagnose this Tom 805 466 4719

 

[Dezertracer812]

I will post pics soon. The boat went into the shop to have the timing curve adjusted, an oil leak addressed and a new tach. I'm going to run the boat again this weekend to get an accurate tach reading then it will be time to address the impeller. I appericate all the feed back. I'm hoping my tach is high and my 6800 is only 4800. At 6800 rpm I still have throttle so boat may go faster I just didn't push it because rmps were reading so high.

 

[Dezertracer812]

Ok so I ran the boat today with a new tach. The boat ran 50mph at 5,000 rpm and gps said 68 mph at 6,000. Would you still suggest an impeller change? Will i see an increase in top speed? I'm thinking I want max rmps to be 5,500.

 

[jetboatperformance]

Ok so I ran the boat today with a new tach. The boat ran 50mph at 5,000 rpm and gps said 68 mph at 6,000. Would you still suggest an impeller change? Will i see an increase in top speed? I'm thinking I want max rmps to be 5,500.

Something is still wrong , your HP vs your tach,GPS and Impeller cut don't add up IMO Tom