Prop Advice Sundowner 205 / Penta SX 5.7 320hp

[stant1man]

Hi Guys,

I am aiming for 50mph or more and better accelleration.... can anyone help.

Here are my current specs...

Slow Accelleration and lower than expected top speed
(previous prop) 23 Pitch High 5 @ 4750rpm/47mph
(Current Prop) 14.5 x 21 Stiletto Bay Pro 3 @ 4450rpm/45mph (Current)
Volvo Penta 5.7 Vortec heads, Holley avenger MPFI conversion 320hp. SX-M 1.79:1
Four Winns Sundowner 205 Cuddy - 21ft 2000 not sure of weight.

I was thinking of changing to either a 19p bay pro 3 or a 20p bay pro 2... My engine has been built to sustain 5000rpm no issues (not stock) so I would like to be landing around this rpm.

Any advice would be gratefully appreciated...

Best wishes,

Stan

 

[500dollar744ti]

Re: Prop Advice Sundowner 205 / Penta SX 5.7 320hp

is your boat really heavy?

as a random comparison, my 22.5' cobia does 52mph on a stock 1990 270hp 350 magnum with a beat up 14.25 x 19p turbo. that's with two people though. it does 48mph fully loaded with 7 people and 65 gals of gas.

i'm trying a 14.75 x 20p solas titan HR-3 next trip out.

 

[Maclin]

Re: Prop Advice Sundowner 205 / Penta SX 5.7 320hp

Most 5.7 260-280hp 22 foot cuddies can hit 50 at about 4800 rpm with 21-23 pitch prop ranges and 1.5 or so drive ratios.

I would offer that your engine does not make 320hp right now based on the numbers you gave. You went from a 23p to a 21p and lost rpm's, something is not right with that engine's tune I'm thinkin'.

In my opinion, with a drive ratio of 1.79 and 320hp from an engine that "has been built to sustain 5000rpm no issues (not stock)" in that boat you should be able to over-rev with anything less than a 23p.