Another "is this the right speed?" question

BlueLightSpecial

Petty Officer 2nd Class
Joined
Dec 2, 2011
Messages
152
I have a 1995 Wellcraft Eclipse 210 SCS. Dry weight is 3100#, 50 gal fuel, I am guessing with only me and gear, about 3900-4000#. It has a 250 hp 5.7 mercruiser, 1.50 ratio, 19"p 3 blade aluminum prop. I get 42 Mph @4600. Does this sound right, plus available locally is a 4 blade 23"p that I may try. I have read that with a 4 blade, to subtract 2" from the pitch, to get its 3 blade equivalent. I am trying to get a few MPH out of her, and wondering if you guys think it would work?
 

Bondo

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Apr 17, 2002
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Re: Another "is this the right speed?" question

I have a 1995 Wellcraft Eclipse 210 SCS. Dry weight is 3100#, 50 gal fuel, I am guessing with only me and gear, about 3900-4000#. It has a 250 hp 5.7 mercruiser, 1.50 ratio, 19"p 3 blade aluminum prop. I get 42 Mph @4600. Does this sound right, plus available locally is a 4 blade 23"p that I may try. I have read that with a 4 blade, to subtract 2" from the pitch, to get its 3 blade equivalent. I am trying to get a few MPH out of her, and wondering if you guys think it would work?

Ayuh,..... Yer already outa horsepower,... yer only pullin' 4600 rpms....

Jump Up to a 23" prop, 'n it'll be luggin', Bad, 'n gutless... a dog, No power...

Maybe another style 19", to squeeze a few more rpms/ mph...
 

steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
Re: Another "is this the right speed?" question

Your just about at the max,but:: Be sure the motor is in excellent tune,compression check.Be sure timing is set right and advancing as it should. Throttle opens all the way. Bottom is clean and smooth.
Your slip is about 23%.Even allowing for a heavy boat thats a lot.
Is the prop in excellent condition?
AS suggested a Solas Amita 3 blade 19" prop might get you some improvement in results.
If it has a hydrofoil on it take it off for now.If it has trim tabs back them off all the way and test.
 

BlueLightSpecial

Petty Officer 2nd Class
Joined
Dec 2, 2011
Messages
152
Re: Another "is this the right speed?" question

What I think I will do, maybe this weekend, Check the timing, and put the tach lead on my fluke, and verify the WOT rpm. My Prop calculator smartphone app, confirmed a 23% slip. What is a good % slip for a boat like mine? For some reason, 18% is in my head. BTW, as per my mercruiser owners manual, mine is the 235 horse, not sure if the 15hp made a huge difference or not. That stupid smartphone app does not ask for weight or HP, but asks for pitch, gear ratio, engine rpm, and speed. Not sure how accurate it is. Would I be better off to go stainless?
 
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