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FAQ: Three-Bladed Prop


I am in the process of buying a Catalina 34 Mk II. I have seen the discussion on going to the three bladed prop vs. the standard two blade prop. My question is do I still look toward getting a 15 X 10 pitch prop even though the newer Catalina's have a 30 hp vs. I believe the older 25 hp diesel? Will the increase in horse power make going to a 15 X 9 pitch prop more likely? Do any of the newer Catalina 34 MK II owners have the three bladed option?  

I have a 1988 Catalina 34 with the MXP25 engine.  In 1992 I had my prop repitched from a 15 x 9 to 15 x 10.  At 2500 RPM on the engine my over water speed on a calm day went from 5.0 knots to 6.1 knots.    It will depend what the output in RPM's the shaft is turning as to what speed you will get.  If you can find out what the shaft RPM's are for a given engine RPM between each engine, then you should be able to make as wise decision as to either the 15 x 10 or 15 x 9 prop pitch (NKnutsen@aol.com

I have a late mkII with the 30 hp engine and the standard 2-blade prop.  I believe my prop is 15x10.  There's plenty of power with the 30hp.  I don't see any need to go to a 3-blade prop unless its a feathering prop and then only for added smoothness under power and reduced drag under sail. I don't think the benefits of a 3-blade fixed prop are worth the drag (Bob Greenhaus).  

Don''t let the boatyard talk you into getting a "powerboat" prop - you need a "sailor" prop, which has considerably less mass.  If you get a 3-bladed prop that isn't a "sailor" prop, your engine will smoke! (Bryan Pfaffenberger)

The 15 X 10 is the right pitch for the XP 25 The factory used a 15 X 9 based on some unknown factor , most of us have up grade the pitch to 10 , I did it the first year of ownership, 1988. You will like it better. Dave C34 # 713 NONSENSE

Just had my 15X9 repitched to 15x10 based on numerous recommendations to address my slow speed problem. Haven't been launched for the season yet, but am looking forward to seeing the results. I'll let you know. by the way, with the 15x9, temp stayed at 165 degrees at 3000 rpm's, so that helped convince me that an extra inch of pitch wouldn't be detrimental to the engine. Ed Tail Wind #866

Important: The opinions expressed here are those of the individual contributors to this page, and not those of the Catalina 34 National Association or Catalina Yachts, Inc. Additionally, this material has not been reviewed by Catalina Yachts, Inc. for technical accuracy. This page's maintainer cannot guarantee the accuracy of this information or the desirability of suggested modifications or upgrades. Please obtain assistance from a competent marine mechanic or boatyard prior to making any significant modifications to your vessel.   

Last modified by Phil Imhof, Wednesday, August 11, 2004 . Copyright 2001 by Catalina 34 International Association.  All rights reserved.