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bassislife

Yamaha 50 4-stroke prop size?

12 posts in this topic

I have a Yamaha F50 4-stroke tiller on a Alumacraft 165 Classic.

In calm water I can only get the backtrolling speed down to 1.40 mph.

I was hoping to do better then that with the adjustable speed, but thats it.

I don't like using the drift socks so I was wondering if my prop should be changed to a lower pitch?

My prop is a 12 pitch and I believe that there are only 2-sizes lower, a 11 and a 9 1/2?? Not real sure on this.

My top end now is 28 mph (one person) and 26 mph (2 people).

Does anyone have the lower pitch prop on there yamaha? and if so how low can you get the trolling speed down.

Thanks in advance!

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Do you know your max rpm at wot right now? You should be between 5000-6000 and to be honest with you, I'd be more concerned with that number. If you drop in pitch you will increase the rpm's at wot and if it is over 6000, you risk engine damage.

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5300 rpms. I would be careful in backing off the throttle, getting it down to where it should be.

But we also make a trip up to Canada with around 1500lbs in the boat. I think a lower pitch prop should do a better job getting it up to a plane also.

Does anyone have a lower pitch prop that has some experience with the the performance of it?

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Curious, are you sure its a 12" pitch prop, and not maybe a 12" diameter prop? you should be turning more than 5300 on that boat, my boat is very similar in size, and is running closer to 5800 rpm with a Yamaha F40 on the back running a 3 blade aluminum 11.6" diameter x 12" pitch prop. The gear ratio is 2.0:1 and I figure the 50 should be able to pull harder than that. Are you having difficulty getting on plane currently?

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If you are turning 5300 then you have room to play, dropping in pitch is definitly an option.

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Dealer told me it was the recommended prop for the boat. Last number was 12 so I'm assuming it is a 12" prop?

Boat does up and plane very quick now. The dealer said that there was only 2 props lower. Would you go to the 11" or the 9 12" ??

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Well you could drop to the 11 I suppose, dunno if I would go as far as the 9.5" pitch, if you use the rule I was told a couple weeks ago, of 300 rpm per inch pitch. going down to a 9.5 would theoretically increase your rpms by 750 at WOT. so that would put you into the danger zone, potentially damaging the engine and bumping into the rev limiter.

How slow do you want to go? I use a 80# Vector 3x, and that works really good. I am afraid if you drop to a 11 pitch you would be wasting $100 just to drop one tenth of a mph.

You might have to drop to a small kicker like a Yamaha F4 or F6 if you want a gas powered option.

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I wouldn't mind having a spare prop when we go into Canada anyway. Best place to buy one??

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I used soderblooms for the prop I purchased about 3 weeks ago. Jay was a really knowledgeable guy, and good prices too.

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Just found out my prop is a 10 5/8 x 12. I can get the RPMS up to about 5900 with a max trim up. The next lower prop pitch is a 11 5/8" x 11. I'm guessing the RPM's trimmed down will be around 5700 and the wider prop should make it troll down a bit? By the way solderblooms wanted $200 for the same prop I found in Annandale for $85.

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I wouldn't put less pitch on it.

How are you getting your speed?

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I have two f 50's on 18' boats, one is a carburated and one is a fuel injected, they both have 10 3/8 X 13-B props on them. The carburater motor trolls 1.6 mph going forward,

the fuely trolls 2.2 mph going forward.

I never touched either motor, that's the way they came.

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