Volvo Prop Change, RPM Change

Joined
Apr 10, 2012
Messages
7
I have a 1995 Wellcraft Eclipse 233, with a Volvo 5.8FL (ford 351) (4 Barrel Holley). It has a Volvo Duo Prop, and currently I am running the B4 setup. The boat is 3900 lbs dry. WOT is supposed to be 4000-4400 RPM. Currently it will spin over 5200 RPM. (Probably not for long)

Does anyone have a feel for how many RPM I will drop going to a B5, B6, C5 or C6?


Thanks,

Wade
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Re: Volvo Prop Change, RPM Change

before you do anything, get a shop tach and verify the RPM you think you are running is the actual RPM.
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: Volvo Prop Change, RPM Change

I was going to attach a PDF of the Volvo Prop Guide 2005-2006 but the attachments dropdown is not giving me much to work with, so here is a snippet of the B series page. This will show the top speed range for the top RPM range of the engine shown on the left. You can also use any of the ranges shown as relative top speed increments between the Bseries props.

B series prop page.jpg
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,306
Re: Volvo Prop Change, RPM Change

see PM
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: Volvo Prop Change, RPM Change

I meant to include these approximate pitch refreences for each B series number...


B4 ~ 21
B5 ~ 23
B6 ~ 24-25
B7 ~ 25-26

These are based on numbers obtained usimg a prop calculator with accurate B5 numbers, then extrapolating the others using 10% slip. Using your speed with a prop calculator you should be able to obtain a usable RPM drop by pitch.

Here is a link to a simple prop calculator...:

http://www.marksmarineinc.com/prop_calc.aspx
 
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