Propping 35'

Rlmdrydock

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Hi all. In first few hours of ownership of 35 Duffy. 1986 cored hull with 3116 cat 300hp. Think I did pretty good on price. Perhaps buyers were put off by cored hull and '99 3116 with 750hrs.
So far all checking out ok. Sure to be some wet spots and a lengthy list of improvements for fall.
To the point I've got a rated max rpm of 2800. Prop is currently 24x 22pitch. wot 2850rpn in cabin and 2750 at flybridge. I understand its good to be wot slightly over rated max. Am I just right or would a move to 21 pitch be better. Prop needs replacement as it's in rough shape. Pitted and thin. Will be checking for stray current. Yeah zincs we're in rough shape.
 

djmarchand

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Check the wot rpm with a phototach. That is the only accurate way to measure rpm if you are concerned about propping. Google it. One should cost about $50.

David
 

Brooksie

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Good advice, both your tachs are likely wrong so adjust them both first. Also be sure of your gear ratio b/4 you start thinking of props.
 

Toolate

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1998 36' Sabre Express CAT 3116TA's, 2015 ROS Scotia 16 Etec 50
If the prop is the original and as bad as you say, it may have lost some pitch over time its possible that a new one will get you where you should be as well. SOunds like you might just be looking for 50 rpm or so?

Bought a photo tach from Harbor freight- think it was $20.

(thanks Larry)
 
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BillD

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Check the wot rpm with a phototach. That is the only accurate way to measure rpm if you are concerned about propping. Google it. One should cost about $50.

David

Good advice, both your tachs are likely wrong so adjust them both first. Also be sure of your gear ratio b/4 you start thinking of props.

RLM,

These two members are dead on with their advice.

Me??, if I was buying a new prop for a boat new to me I'd get accurate (photo tach) full loaded (boat as heavy as you'll ever use it) WOT rpms.

Knowing the rpms I'd have a propeller specialist (Accutech in Dover NH comes to mine) prop the engine to 2900 WOT rpm.

Your engine will be more responsive @ ALL rpms and your engine will thank you down the road in less wear and tear and maybe just maybe last a bit longer than flogging it to death by over propping. :D

For what it's worth,

Bill D
 

andy65

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Northern Bay 36
What is a good price? Where did you find it? PM me if you don't want to say in the forum. I would like to know what these are actually selling for.
 


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