Reply With QuoteHow can 375 hp spin up to 5900? Something's fishy.
A friend is looking to buy an 03. 21' Aftershock open bow, with a 496 bbc 375HP, and a berkeley set back pump. (not sure impeller size) with diverter , no droop. boat has 83 hours on it.
went for a test run and with 4 people (3 adult males, 1 adult female) the boat ran at 5900 RPM @ 53 MPH on speedo. (not GPS)
can anyone tell if this is the norm for these boats? he says it seems a little sluggish, but then again he is used to an 18' jet boat. he just doesnt want to have to find out the hard way that the pump is worn out. any ideas?
How can 375 hp spin up to 5900? Something's fishy.
I have 04 21 eliminator jet with a 496 mag. 55mph is all your going to get. It's a heavy boat and that jet eats up the horsepower.
the post is for a friend, he just called and asked me to post to get some opinions. thats all the info i recieved.
5900 RPM with 375HP? id have to know what cut the impeller is. but id say its possible. and a 21' hull spinning 5900rpm @53 mph seems respectable to me. but the more imput the better. so lets here em.
Vic, its 4900 RPM's at 53 MPH. I might have told ya wrong. Sorry.
Originally posted by tool 'n' jet
I have 04 21 eliminator jet with a 496 mag. 55mph is all your going to get. It's a heavy boat and that jet eats up the horsepower.
Thats what I was lookin for. Thanks Tool.
Victor,
here's what came to mind when reading your post:
#1- If the engine is cammed to where it needs to run 5900-6000 rpm to get to full power, then it is probably running an impeller cut to achieve that rpm.
#2- My boat (heavy Omega openbow) ran quite a bit faster mph wise, with a taller impeller than it did turning higher rpm's with a smaller impeller. We discovered this when Duane was helping me go through the set-up for max speed.
It surprised me that it would run faster turning less rpm with an A impeller than it would turning more rpm with a B.
Duane told me that this was common on heavy boats. IE- more water out the back=more boat forward, he had seen it many times with heavy boats.
So, in essence, what I'm trying to say is that he could possibly gain some mph by installing a new cam which would develop max torque/HP at a lower rpm, and going with a larger impeller.
Ken F
Thats about what my 01 Carrera does. Marine Power Sport Pack 380 HP 454, The boats 20 feet long, heavy and solid. Goes great with a load of people but does mid 50's and thats about it. It hits 5000 rpm...no trouble getting a move on just no big top end speed.
Here are my numbers, 88 commander 21ft. openbow, it tops out at 50-52 mph while turning the tach up to 4200 rpm's.
Stock 454 (330hp) with hyd. diverter.
Originally posted by Doug H.
Here are my numbers, 88 commander 21ft. openbow, it tops out at 50-52 mph while turning the tach up to 4200 rpm's.
Stock 454 (330hp) with hyd. diverter. Someones done there math building that
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