rpm question

[BOOGEYMAN]

I have a 21 ft sleekcraft tunnel V with a 502 and a berk with an AA. The boat runs 64 gps but only spins 4700 rpm. My question is would I gain anything by going to an A or B cut impeller?? It just dosent sound like it is using all of the power at 4700, I think it would be much happier arround 5200 to 5500. I just dont want to switch the impellar and only get more rpm but no gain in mph.
Thanks for your time.
Travis.

[YeLLowBoaT]

By going to a smaller impeller you tipcally gain mph and lose some "hole shot".
I would think you would be happy with an "A".

[Duane HTP]

What 502 do you have? 502/peanut heads, 425 hp 502, 450 hp 502 or 502/502? The answer to your question could be quite different, depending upon which engine you have.

[BOOGEYMAN]

Duane, it is a 502/502.
Thanks.

[jbone]

I've got the 502/502 in my 21 ft shockwave (3500 lb vee hull).
With stock exhaust I turn my American Turbine/Dominator A impeller 5000 rpm at 67 mph.
I'm hoping with Lightning's I'll get 5200 rpm.
J

[BOOGEYMAN]

Thanks! I think my boat is lighter than yours so maybe with an A, around 5200 i can see 70 on the gps.
p.s. that is quite a rooster you got there!!!!

[centerhill condor]

nice camel toe too!

[Duane HTP]

Yes, a smaller cut impeller will help with that 502/502/. We special grind a solid roller camshaft specifically for jet boats that really wakes that motor up too. On that big of a boat, If running an Aggressor impeller, I'd go with an A/B cut. If berk or Dom, I'd run an A cut.

[BOOGEYMAN]

Thanks Duane!!

[1tricky1]

I have a 21 ft sleekcraft tunnel V with a 502 and a berk with an AA. The boat runs 64 gps but only spins 4700 rpm. My question is would I gain anything by going to an A or B cut impeller?? It just dosent sound like it is using all of the power at 4700, I think it would be much happier arround 5200 to 5500. I just dont want to switch the impellar and only get more rpm but no gain in mph.
Thanks for your time.
Travis.
Nice looking Sleekcraft! Do you have any more photos? I have a 79 Sleek SST with a BBC pushing real close to 500hp. I have the "e" pump with an Aggressor bowl, stuffer, droop, shoe and rideplate and a Place Diverter. She runs a solid 75mph when the load is light. I spin an Agressor B cut at 5400-5500. What pump do run? Any mods to the pump?

[BOOGEYMAN]

Looks like we have the same hull, mine is a 79 as well!! The pump is a 12jc and I dont think it has any mods. I have a droop and a place diverter as well. It had a loader when I bought it but I took it off just to see if there was any changes and there wasn't so I just left it off.
What do you gain from a shoe and rideplate?? I would love to get mine where yours is at. Thanks for the help!
Travis.

[1tricky1]

Looks like we have the same hull, mine is a 79 as well!! The pump is a 12jc and I dont think it has any mods. I have a droop and a place diverter as well. It had a loader when I bought it but I took it off just to see if there was any changes and there wasn't so I just left it off.
What do you gain from a shoe and rideplate?? I would love to get mine where yours is at. Thanks for the help!
Travis.
The shoe and ride plate mostly come into play at speeds above 65 mph. It helps keep the pump loaded at those speeds. With you running 500 hp and basically having a better pump than the "e" pump I would think you should be running 70+ with that hull. I think your headed in the right direction by cutting the impeller down from that huge AA. I'll bet 5400 rpm is very close to peak hp for your 502 and I'm sure you'll see speed gains going in that direction. Best of luck to you!

[Scoobinator]

I have a 21 ft sleekcraft tunnel V with a 502 and a berk with an AA. The boat runs 64 gps but only spins 4700 rpm. My question is would I gain anything by going to an A or B cut impeller?? It just dosent sound like it is using all of the power at 4700, I think it would be much happier arround 5200 to 5500. I just dont want to switch the impellar and only get more rpm but no gain in mph.
Thanks for your time.
Travis.
I have went through the similar situation as you with rpm's. With impellers I have learned that each size smaller you should gain 200 rpm. You should go with a B and not any smaller because your pump will lose efficiancy a B is a alround good impeller And for your hole shot you should invest in a inducer.

[BOOGEYMAN]

Thanks guys!!!!

[Bense468]

If I was you I wouldn't go with a "B" an "A" will get you right where you want to be. With a B in that big of boat you will be slower out of the hole and your cruise RPM will be much higher resulting in a less fuel efficiency. Just my 2 cents

[RICHARD TILL]

go with b or a/b cut. ask a winner what cut he runs. not very often will he say an a cut.

[Bense468]

go with b or a/b cut. ask a winner what cut he runs. not very often will he say an a cut.
Light NA boats, and going to spin smaller impellars (ab's, B's, BC's, even C's)Fuel boats are going to run bigger impellars (AA's, A's). Ask some of the blown injected alky guys what they are running. Most are probably running bigger then a B if they are producing lots of power and can pull the RPM. Thats a race boat though.
This is a cruiser, you want to get a bigger heavier hull out of the water and pull skiers, tubers, get decent gas milage, and maybe lose 1-2mph on the top end (or maybe not) run a larger impellar. I agree with Duane to I to back it off a little from an AA to get a little more RPM's out of that 502/502. Like he also said, a new cam, and even some head work is an option.
All depends on what you want to do.