Speed vs. Rpms

[BBCJetovator]

Hi, I need some help. I just had a mild rebuild on my 454. The motor is putting out around 410Hp. My boat is a Taylor 22ss, its got a cuddy cabin and it's pretty heavy. the pump is a berkely 12jfa with jetovator. I just took it out last weekend for the first time with the fresh motor. At wide open throttle im pulling 4600 rpm. dont know what impeller im running but it seems like the boat isnt as fast as it should be. I talked to dons pump and he thinks my cam is too big? Anyone have any ideas?

[SuckMyWake]

Hi,
You need to find out for sure what impeller you have. Then you can see if the engine is revving to the correct RPM for the impeller you are using. If you have an AA impeller, 4600 RPM would mean you are producing about 360HP. With 410 HP and a AA impeller the RPM shoud be 4800. You will lose RPM with a less radical camshaft. You might get more torque, but to take advantage of it, you would need a new impeller. The impeller must be matched to your specific engine output!
Hope this helps get you on the right track.
-Todd

[Blown509Liberator]

hey BBCJetovator
I had a 20' Baja TC cuddy. It had a F pump in it. First the F pumps had a different trim the the old Jet o vators. Second with a little hp you cand make it run. We still have this boat and with a 502/502 a loader and a Legend "A" cut impeller we pull 5000 Rpm's just over 70 mph. I must tell ya we lost the f bowl for a AMT and a put a droop and AMT trim nozzle. It makes for a nice set up.
MikeW

[jet496]

SuckMyWake sounds like he knows what he's talking about. I have a 496 HO rated at 415 hp with a AA impeller and it turns 4800 rpm (a blond hair over)and runs over 60 mph. I was actually thinking I could turn more rpm's with an A cut, but I don't want to chance hitting the rev limiter (was with a B impeller & it's annoying). I'm perfectly happy right now with the performance (Family boat).

[Inciong_A]

What's the easiest way to find out what kind of impeller I have? The plate on the jet (Berkeley) says, "JG-A". Does this mean that I have an A impeller? Otherwise, can I look through the cleanout to see a stamp or something? Thanks.

[phillyray]

The tag on the pump saying jg-meaning it's a (G)pump,split bowl,thats a good thing.Now the (A) says it was assembled with an (A)sized Impeller.Very common in a (stock) factory boat.However a previous owner may have had the Impeller cut down to a A-B,C to allow higher rpm.Or could have installed a (AA)larger for more efficient cruising speed.Hope this helps.PhillyRay. P.S. sometimes they stamp the Imp.Ex.I can see my letter when under the boat changing the speed loader.(thats with a Aggressor-A- Impeller)not to sure about others?