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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

High thrust prop

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RichardG
Admiral

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USA
990 Posts

Initially Posted - 07/04/2002 : 01:00:29

Replacement props for my 1985 Suzuki 6 hp long shaft come as follows (diameter x pitch):

7 7/8 x 5 1/8
7 7/8 x 5 7/8
7 7/8 x 6 1/2
7 7/8 x 7 1/2
8 1/2 x 7 1/8

Which one would be considered "high thrust" and would be most appropriate for pushing a C-25?

RichardG 81 C25 SR/FK "Sanity"

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 07/04/2002 : 17:15:02

Probably the 7-7/8 x 5-1/8. What are the specs for your current prop? They should be stamped on the hub. I think you mainly want a lower pitch--a larger diameter or more blades should also help, but the pitch is the primary issue, letting the engine and prop work better when the boat is moving slowly or not at all. You may find that you run closer to full throttle to get to cruising speed, but should stop and start a little faster.

If you have a knowledgeable dealer (for any brand) in your area, you might get their opinion--as if you were thinking of buying a new motor. (IMHO, except on a small lake, a 6hp 2-stroke with a 20" shaft is marginal at best on a C-25, regardless of the prop.)

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette "Passage" in SW CT

Edited by - Dave Bristle on 07/04/2002 17:15:49

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Mike Vaccaro
1st Mate

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77 Posts

Response Posted - 07/07/2002 : 17:17:15

Richard,

We too use a six horsepower engine with a high-thrust prop, and have had great luck with the combination (2001 Johnson)--your best bet is to find a dealer that is knowledgable, or go directly to the manufacturer for a recommendation. The standard "generic" prop shipped with your motor is probably designed to produce rated horsepower at speed. Since our boats move rather slowly, the trick is to increase prop diameter and decrease pitch (the distance that the blade moves forward through 1 RPM, measured in inches). This will allow the engine to produce more power at lower speed, hence the term "high thrust."

Best of Luck,

Mike Vaccaro on the "Swoose"
84 TR/SK #4707

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RichardG
Admiral

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USA
990 Posts

Response Posted - 07/08/2002 : 14:31:52

Dave & Mike:

Thanks for the advice. I will continue my quest for a Suzuki prop "expert". While the local Suzuki shop has a good overall reputation around here, they did not have much information about props other than what is available for this model.

The specs on my current prop are 7 7/8 x 7 1/2. Four blade props are not available for this model. While I can reduce the pitch to 5 1/8, the diameter would remain the same. Alternatively, I could increase the diameter to 8 1/2, but the pitch would remain the same. It appears there is no way to reduce the pitch and increase the diameter. It would be nice to talk to someone reputable who knows from experience that starting/stopping performance of these small Suzukis can be improved without materially sacrificing cruising performance. I think I'll try south...

Dave -- I'm sure you are aware that some folks do not agree with your assessment of a 6 hp 2-stoke long shaft as marginal at best on a C25. It has proven to be considerably more to many on our small lake here off the Left Coast. Plus, it's mine -- those bigger, heavier, more expensive, more difficult-to-fix and less reliable engines in the store are not.

RichardG 81 C25 SR/FK "Sanity"

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RichardG
Admiral

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USA
990 Posts

Response Posted - 07/08/2002 : 14:33:43

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 07/09/2002 : 16:25:29

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
Dave -- I'm sure you are aware that some folks do not agree with your assessment of a 6 hp 2-stoke long shaft as marginal at best on a C25. It has proven to be considerably more to many on our small lake here off the Left Coast. Plus, it's mine -- those bigger, heavier, more expensive, more difficult-to-fix and less reliable engines in the store are not.
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
Richard: I'm glad you find it to be adequate or better... On Long Island Sound, I wouldn't be comfortable with the shaft length (20"?) or power for handling our square waves in a headwind. Your assessments of the ones in the store have merit--except perhaps for the "less reliable" part... In my experience, not running oil through the carb and chamber can improve starting and general reliability. Besides, for brute-force reliability, I'd stack my 4-cycle Briggs and Stratton lawnmower engine up against any 2-cycle ever made! Few engines are treated worse than that one! <img src=icon_smile_wink.gif border=0 align=middle>

Regarding props, have you investigated Michigan Wheel or other specialists? Apparently, you can go up to 8.5" in diameter, so there's must be a lower pitch prop that size out there somewhere, but probably at a somewhat higher price than from Suzuki.

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette "Passage" in SW CT

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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.