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  #1  
Old 06-23-2013
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Small outboard plastic prop?

So I snagged an Avon Redcrest and a 1976 Johnson Seahorse 2hp from craigslist for $400. I'm pretty happy with the two of them although the redcrest is still a bit too large to comfortably stow on my 26'.

However I took them out on a nearby lake and for the high drag soft bottom inflatable it felt like the engine was overpropped and unable to get to max rpm. Going from 70% to 100% throttle gained little.

While looking for some other parts I noticed that the new props are plastic with an interesting design - sort of long curved blades. It struck me that in practice the plastic prop might flex under load and effectively reduce it's own pitch.

Is the plastic prop actually designed to flex like this or am I overthinking it? Would it be a worthwhile upgrade?


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Last edited by asdf38; 06-23-2013 at 08:15 PM.
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Old 06-23-2013
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Re: Small outboard plastic prop?

I had a plastic prop on a Honda 2 HP outboard. I could actually flex the tips of the prop a little bit with my fingers, so I would guess it would flex under full, load. In any event, it provided plenty of thrust on both a soft floor inflatable and a 12 foot Jonboat. If it is the same or lower pitch as the existing prop it should let the motor rev more at WOT?

Paul T
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Old 06-24-2013
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Small outboard plastic prop?

Is prop aluminum and when u remove it isthe area where the prop shaft goes into the prop rubber? When props get old that rubber breakdown abd it will cause it to slip reducing thrust. If it is not that you are prob just incorrectly pitched. See what the pitch number should be for your propellor beforeyoubuya replacenent. Plastic props are fine and the flex is built in but they dont last forever
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Old 06-24-2013
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Re: Small outboard plastic prop?

Quote:
Originally Posted by ScottyG24 View Post
Is prop aluminum and when u remove it isthe area where the prop shaft goes into the prop rubber? When props get old that rubber breakdown abd it will cause it to slip reducing thrust. If it is not that you are prob just incorrectly pitched. See what the pitch number should be for your propellor beforeyoubuya replacenent. Plastic props are fine and the flex is built in but they dont last forever
I can only speak from my own experience. I had a Honda 2HP, with the stock plastic prop, for 28 years, put many, many hours on it, broke a number of shear pins on rocky river bottoms. Maintenance consisted of smoothing off the rough edges with a file. Absolutely no problems with the prop, or the motor. Other plastic props may vary?

Paul T
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Small outboard plastic prop?

Check your engines height on the transom aswell as u might just be cavitating. Before i was a sailor i spent alot of time on a 75+mph Hydrostream i restored over 3 years and learned rules for O/B props the hard/expensive way:
1. thrust bearing must be good (the rubber i talked about
2. pitch must be correct
3. engine height correct
4.stainless is always best( not an option in this case but just saying)
good luck
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