what size prop should i try next???

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rswanson
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what size prop should i try next???

Postby rswanson » Tue Aug 22, 2017 3:20 pm

58' evinrude 35hp lark. 74' aluminum flat bottom 17' monarch. in gear, throttle blade at W.O.T, timing is set to best i can figure. starts very easy with pull rope, hot or cold. starts perfect with starter, also. idle's in gear 650-700 rpm all day. runs extremely well. the only prop i have is a 10 3/8" x 12 1/2". its only turning 3800 rpm with full tank of fuel, 2 people and all fishing gear. i would like it to turn 4500 rpm at W.O.T. in gear with my rig. i ordered a used 10" x 9 1/4" on ebay, but now thinking it will be too high rpm. thank you in advance.

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wbeaton
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Re: what size prop should i try next???

Postby wbeaton » Tue Aug 22, 2017 3:54 pm

Its all trial and error. You can plug all your data into a handy little calculator to tell you the correct pitch for your boat, but they aren't very accurate. Trying different props and noting your results against a tach is the best thing you can do. Used props are fine, but make sure it is in nice condition. By nice I mean like new. A few nicks and dings make a huge difference in performance as does a smooth vs rough texture. Finally, the big round blade props of the 1950's OMC's are so much better for pushing heavy loads than the newer style props with the narrow blades. I think 9 1/4" is a good next step. Besides, even if it over revs it might still be useful for the days when you take a third passenger.

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Garry in Tampa
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Re: what size prop should i try next???

Postby Garry in Tampa » Tue Aug 22, 2017 7:34 pm

Look for a 0377410 propeller, it is 10-3/8" by 11-1/2". That was replaced by 385955 and are no longer available from the factory. A really old dealer may have one on a back shelf. On the other hand, Steve Woods gave a demonstration at Tomahawk on how to re-pitch propellers. He used a really big Crescent Wrench - - - :D
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punchbug
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Re: what size prop should i try next???

Postby punchbug » Tue Aug 22, 2017 8:17 pm

I will look to see what NOS I have tomorrow. I have about 30 props from an old OMC repair guy. Chances are it is there and the price will be super low as well. Plus shipping of course.

outbdnut2
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Re: what size prop should i try next???

Postby outbdnut2 » Tue Aug 22, 2017 8:45 pm

I agree with Garry, 11-1/2 inch pitch sounds about right. I've got 3 old boats I run 1950s 35s on, so I have a pretty good idea of what going down 1" in pitch will do. Propco has a new 10-3/8 x 11-1/2 for $84.00.
Dave

http://www.propcopropellers.com/online- ... y=19177439

rswanson
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Re: what size prop should i try next???

Postby rswanson » Wed Aug 23, 2017 12:36 pm

thx for the quick replys. the 10 x 9 1/4" should be here today or tomorrow. i'll test it and post the results. as for a 3rd person in boat, it only dropped 100 rpm and 1mph with the 10 3/8 x 12 1/2 when i added a 160 lb buddy in boat. punchbug, i'll pm you after i find out how the 10 x 9 1/4 works out. on my 58' 18 hp evinrude mounted on same boat, i lost 200 rpm when i changed from a 9x9 michigan (4700 rpm) to a 9x10 solas (4500 rpm). so i hope about 200 rpm rise for 1" of pitch drop out of the ole 35. thx again for all replys.

amuller
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Re: what size prop should i try next???

Postby amuller » Wed Aug 23, 2017 12:56 pm

rswanson wrote:58' evinrude 35hp lark. 74' aluminum flat bottom 17' monarch. in gear, throttle blade at W.O.T, timing is set to best i can figure. starts very easy with pull rope, hot or cold. starts perfect with starter, also. idle's in gear 650-700 rpm all day. runs extremely well. the only prop i have is a 10 3/8" x 12 1/2". its only turning 3800 rpm with full tank of fuel, 2 people and all fishing gear. i would like it to turn 4500 rpm at W.O.T. in gear with my rig. i ordered a used 10" x 9 1/4" on ebay, but now thinking it will be too high rpm. thank you in advance.



So you want to increase rpm by 700 and your drop in pitch will be 3 1/4. That's a large pitch change and you could end up with something intermediate. But no use speculating before you try it. Agree that taking out the nicks and a smooth finish can make a big difference.

Interesting article here on checking out propellers: http://www.aomci.org/members/library/ShipshapeProp.htm

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VinTin
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Re: what size prop should i try next???

Postby VinTin » Wed Aug 23, 2017 12:59 pm

Sometime when pushing a heavy load a 4 blade prop may work out better than a three blade. Like Wayne mention....prop surface area becomes an important factor when pushing heavy loads. I consider your application a fairly heavy load.

For my 1957 35hp motor on a Feather Craft Vagabond I carry a 4 blade 10" X 11" prop for those time when towing someone a long distance. Granted when towing I'm not running high speed but this prop feels like I've dropped the motor in 4x4 drive.

Your use of a tach shows you are going to find the best solution for your combination. A point not to be overlooked is that the motor has to be in optimal tune before testing out props. It sounds like yours is but you've got to be sure. Otherwise all bets are off.

rswanson
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Re: what size prop should i try next???

Postby rswanson » Thu Aug 24, 2017 9:21 pm

looks like i didn't do enough research and ordered the wrong prop. oh well, lesson learned. glad im only out $27.25. but its a very nice looking prop and im sure it'll work well on the right outboard. the # is 309946. it doesn't fit my evinrude 35514-22620.

yes, i would like to increase the rpm from 3800 to 4500. jus trying to get all i can with what i got. seems like the CORRECT prop would get it there.
i like to run tach's on all my old junky motors, outboards and old snapper comet mowers. jus a piece of mind for me. i've been running tiny tach brand for a while now and jus recently trying cheapo ebay tach's. cheapos are within 30 rpm compared to the tiny tach brand. even closer on my junky truck.

as far as the tune, new coils, points (gapped at .020"), condensers, leads, boots, plugs (autolite 303 gapped at .030")), water pump impeller, 143* thermostat, needle jet packings, float set level to bottom of upper carb base (when turned upside down), needle and seat, fuel filter, fuel hoses. fuel mixture is 6 oz of tcw-3 to 1 gal of 93 octane gas (with up to 10% ethanol) 21.3333:1 is close enough. i also add 1 oz of seafoam to a gal. of fuel. carb settings work best when low speed is set 3/4 turn out from seated, high speed tops highest rpm at 1/2 turn from seated. last cold compression test on 7/27/17, showed 110 lbs on bottom cylinder, 120 lbs on top cylinders. if i missed something on tune, plz let me know.

i going to slow down and find the right prop for this rig.
again, i thank you all for your time to reply, rick

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wbeaton
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Re: what size prop should i try next???

Postby wbeaton » Fri Aug 25, 2017 12:42 am

That's too bad. I was hoping you were going to give a performance update with the new prop. Please keep us posted on your progress.


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