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Prop Sizing

gogittumgogittum SW New MexicoPosts: 2,311 Captain
I've come up with a couple of strange things with new props.

The 15 hp Johnson motor had a very well used prop on it that gave me 20.5 mph on the 16 ft boat - and it's stamped 9 1/2 x 10.  It measures 9 1/2".  Beautiful.  I ordered a Solas spare for it on Alex's rec that came in a box marked 9 x 10.25, which is what I ordered.  New prop gives me 22.2 mph.  Fine and dandy and I love it, but the prop is stamped OA 14 21.  My Mk I eyeball says it's not even close to 14"....??  It's also stamped with a part # and "Solas."  Whaaat ??  Measured it, going from center of hub to tip of one blade, then doubling it - 9".  I emailed the seller but they didn't have an answer and referred me to the mfr.

No big deal for now, but in future someone might want to order a spare and what will they go by ??  No way is that little motor going to turn a 14 x 21 prop.

Then I bought this Suzuki 25 hp and it came with 2 props.  The one on the motor is stamped Solas, a part # and SB 16 20.  No way is that thing 16", so measured it - 9 3/4" diameter.  About what I'd expect.  I don't have a way to measure pitch.

Spare prop for the Suzy is stamped Turning Point and 12 10.  Measured it at 9 3/4".

Any thoughts ??  Seems some strange to me.  The old Johnson prop is the only one of 4 that measures what it's stamped.


  • chaser48chaser48 San Mateo Fla.Posts: 271 Deckhand
    Suzuki website has article on props I searched df25 suzuki prop sizing
  • gogittumgogittum SW New MexicoPosts: 2,311 Captain
    I broke down and called Solas.  Got a cranky, unpleasant fella on the phone who grudgingly explained that the number I thought was the prop size and pitch - OA 14 21 - is really the date of mfg code.  2nd number - 21119310 - is the stock number, telling us that this is a 9 x 10 1/4" prop.  Wonderful....wonder how they get that out of that ??....they are sooo helpful.

    My Suzuki prop is stamped 421110014, so is a 10 x 14, tho' careful measurement shows it to be 9 3/4" diameter.  With that number I can see 10 x 14, but why don't they stamp the size on them any more ??  The old Johnson prop is stamped 9 1/2 x 10....and it measures 9 1/2".  That's much more helpful.

    Spare Suzy prop is a Turning Point product and is stamped 12 10 & B3 R3 1013, so I assume it's a 10 x 13, tho' it, too measures 9 3/4"..  It's on the motor now and we'll see what it does next time out, tho' it's some chewed up by rocks.  I filed the worst of it smooth and tried for an even contour.  Very differently shaped blades on it - much longer trailing edge.  Still not getting the rpm's or speed I expect.
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