Prop Overkilll

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bayoucat58

Seaman
Joined
Jul 9, 2011
Messages
71
Good morning Admirals and Scallywags, I am running a 19 spline 26 pitch on a 93' 130 Yamahammer which is what the previous owner had on the boat 20' Glassstream. Is That prop overkill? it jumps or eases right out of the hole and scoots along pretty good high 37-40 SOG @ 5300 Rpm. I had a buddy suggest i tone the pitch down some and consider a four blade set-up. What do you guy's think? Have a blessed day With plenty of water under the keel. Just standing by with my Mount Gay Barbados Rum -N- Community dark roast Coffee.
 
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steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Prop Overkilll

Your numbers are really crazy.And I'm sure you have way too much prop.
Right now according to your numbers your slip is around 40% Should be around 10%.
What is "SOG"speed? While Im sure about your prop until we prove your numbers
can't really make a decision. I suspect the tach or speed reading. On your motor a 26" prop at 5300 should produce allmost 60 mph. I do think your prop will endup about 19".
 
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Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Prop Overkilll

OK, got me curious -- what type of lower unit are you using that has a 19 spline propshaft? What's the gear ratio? The only 19 spline I can think of is the Volvo SX and the Merc Fat Shaft.
 
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bayoucat58

Seaman
Joined
Jul 9, 2011
Messages
71
Re: Prop Overkilll

i am gathering all the info myself i just picked it up from the Tech..... shop i will try to answer all of your request forgive me if i am a bit of an idiot.... =^:^= S/B BRB
 
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bayoucat58

Seaman
Joined
Jul 9, 2011
Messages
71
Re: Prop Overkilll

OK I went to the storage and removed the prop it is 15 spline and on the back where the exhaust is it has a stamped 23-K very defined stamp. However up towards one of the cup ends it has a crude hand stamp at least that's what i see... it looks like a 27 or a 21 with the one upside down this is tougher to read. it is on a 1993 Yamaha 130 hp pushing a 21' Glasstream c/c. Is it true, as "i have heard this is a rule of thumb" when you add + 2% of pitch you lower your RPM'S BY 400 and if you subtract - 2% of pitch you gain 400 RPM'S? Thanks a lot guys Cat
 
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Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Prop Overkilll

OK, that makes sense. It's a standard unit. Sounds like the prop was a Yamaha K series at 23 pitch that has probably been redone to act similar to a 21 inch pitch prop. The 200 rpm per inch of pitch only applies when comparing the same make and model of prop.
 
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bayoucat58

Seaman
Joined
Jul 9, 2011
Messages
71
Re: Prop Overkilll

I see so Dhadley would you change anything? I am going to have to take it in to reworked it a few dings ans small bends.
 
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bayoucat58

Seaman
Joined
Jul 9, 2011
Messages
71
Re: Prop Overkilll

Well D was right the prop had been redone to a 21 pitch. I took my old mans advice RIP and left well enough along. She is preforming really well to. Thanks for all of your replies.
 
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