prop size comparing

tazz1985

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Oct 17, 2017
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I have a 23 ft. Sea ray 1985 230 srv cuddy crusier 260 merc Alfa 1 out drive. My current prop is wearing out its old I think it a progressive 17 to 15 pitch 14.5 Dia I tried a 14.5 17 P and rpm's dropped to much 3600 boat is rated for 4600 wot
Has anyone played with other sizes 4 blades etc.
Thx
 

alldodge

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tried a 14.5 17 P and rpm's dropped to much 3600

Dropping to 3600 rpm with a 17 gets me thinking something is wrong. Either the motor is tired, needs a major turn up or the hull is water logged.

Did your previous prop get you to 4600?
 

tazz1985

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Oct 17, 2017
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Hi thanks for taking interest new engine and transom rear stringers 2016
I hit 4400 rpm with current prop but has a a little vibration at low speeds with the new 14.5 17P prop no vibration so pitch might be out a hint I'm thinking of trying. 15 Dia 15P 4 blade but thought I would check the forms to see if anyone has experimented with this type of boat.
 

alldodge

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A 15P 4 blade is close to the same as a 17P 3 blade. It takes more HP to turn more blades, so right now suggest to stay with 3 blades. In any case dropping 1000 rpms going from 15 to 17 is a lot. The normal would be a loss of around 400 rpm
 

tazz1985

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Oct 17, 2017
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Thanks I will give the 15P 3 blade a try. I'm hoping my marine will have a demo to try. The rpm drop was 800 still a lot puzzels me. Have you ever heard blade shape to be a issue
 
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