SoCal Jet Boats

Tech Talk => Jet Pumps => Topic started by: YonaUsti on July 16, 2018, 03:39:26 PM

Title: jet impeller sizing?
Post by: YonaUsti on July 16, 2018, 03:39:26 PM

I took my (new to me) 72 Eliminator Bubbledeck out on the smooth lake last week. I am running a stock, 250Hp Mercruiser 5.7 carb (4400-4800 WOT) motor pushing a Berkeley intake, Bayjet pump with droop snoot, diverter and ride plate. I was getting only 4200 RPM. The RPM and MPH were pretty much equal, 2500rpm = 25mph (GPS), 3500rpm = 35mph, 4200rpm = 42mph....It would not get any higher than that. I don't know what the impeller is. Does this seem correct or can I get more RPMs and speed from a better set up on my impeller?

Previous motor in the boat was an Olds 455 and the jet was rebuilt since then but may have the same jet innards from before

Thanks in advance for any info

Title: Re: jet impeller sizing?
Post by: mash on it on July 17, 2018, 05:33:25 PM

Are the mph and the rpm accurate?
Tachometer checked against a known good one?
Speed checked with a GPS?

Unknown impeller, previously Olds powered,  probably an A. But, with the Bayjet/Berkeley mix-n-match, who knows...

My set-up, Dominator with an A impeller, L31 350 with headers, Eddy intake & 750 Holley, 4600 rpm @ 55 mph, 19' Saguaro. Shoe and rideplate, no Diverter. GPS're and known good tachometer.

I think there is more in your set-up, just gotta find it.

More horsepower, smaller impeller, better exhaust, more cam / compression, the list goes on...

Details, details, need more details.

Dan'l