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  #11  
Old 02-28-2009, 05:28 AM
Bigshrimpin Bigshrimpin is offline
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Location: Onset, MA
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

Quote:
When I first seatrial my 20cc w/ DF140 Suzuki after putting on the bracket, I was running a 20" pitch Power Tech prop and hit 47 kts- 54 mph. Light load with two people, and it was chine walking The hole shot sucked, and only turning 5000 rpm. I now run a 18P prop because I wanted a decent hole shot with heavy loads (30 gal bait well, or full load of scuba gear/tanks). Tops out at 40 mph @ 6000 rpm. I may be a little under proped, but for Sebastian Inlet, I really wanted some low end "get up and go".

Lloyd
http://www.go-fast.com/Prop_Slip_Calculator.htm

2.38ratio
20 pitch prop
5000 rpm

= 40mph with no slip
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  #12  
Old 02-28-2009, 12:57 PM
CaptLloyd CaptLloyd is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

Thanks for the prop calculator, and keeping me honest.

I miss spoke on my early post. I meant 5500 rpm.

I know the number still don't match, but I remember my GPS hitting 47 Kts (I always keep my GPS set to knots). Of course, that was 6 years ago, and I'm doing this from memory .

My boat was very light, I was still putting in back together, no windshield, no bench seat, and very little fuel.

With that 20P Powertech Prop, it was slow to get on plane, and at WOT, I had the motor trimmed way up. I only stayed at that speed for about 5 secs because the squirliness I felt made me uneasy. I made another run at WOT, and had the same result. I definitely remember thinking that this hull was not meant to go that fast

I traded the 20P for a 19P the next day, still didn't like the hole shot, and ended up with the 18P I run now.

That's my story, amd I'm sticking to it

Lloyd
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  #13  
Old 02-28-2009, 02:21 PM
clb33fyxj clb33fyxj is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

Mercury site has a calculator too...

http://appcenter.mercurymarine.com/propSelector/home.do
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  #14  
Old 03-01-2009, 12:11 PM
Fr. Frank Fr. Frank is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

6000 (rpm) 18 (pitch)
----- X -------- X (1-10%) (avg.slip) = 38.7 mph
2.38 (ratio) 1056 (constant)
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Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.

Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!

Currently without a SeaCraft
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury
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  #15  
Old 03-01-2009, 01:11 PM
eggsuckindog eggsuckindog is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

I think your gear ratio is too low - I think my Merc is 1.87/1
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  #16  
Old 03-01-2009, 02:44 PM
Bigshrimpin Bigshrimpin is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

new 140 Zukes are 2.59:1
older 140 zukes were 2.38:1

Merc 175/200 v6 fishing motor are 1:87
Some Merc sportmaster lowers came with 1.62 gears

I believe I read somewhere that Merc 3:0L gears will fit into a 2.5L case, but I never tried it.
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  #17  
Old 03-02-2009, 09:04 AM
Fr. Frank Fr. Frank is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

The GLM catalog lists aftermarket Mercury outboard gears available in 1.5, 1.62, 1.65, 1.75, 1.84, 1.87, 1.92, 1.98, 2.0, 2.06, and 2.3:1, with the 1.5 available only for large 4.75" gearcases, and the 2.3 available only for the 4"/4.25" gearcase. These are not, however, the gears available for the Sportmaster. Those are different gear types. I didn't look at those. The GLM catalog doesn't list prices, just part numbers.

Mercury sells gears for the 4.75" gearcase in 1.5, 1.62, 1.65, 1.75, 1.87, and 1.98:1 ratios,

and for the 4"/4.25" gearcase all of those up to 1.65:1, plus the 2.06:1 and 2.3:1 gearsets, according to my Mercury parts DVD. (And WOW are they expensive from Mercury at about $1000 for a complete set!!!!)
__________________
Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.

Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!

Currently without a SeaCraft
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury
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  #18  
Old 03-02-2009, 10:31 PM
Caymanboy Caymanboy is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

Did you guys go off on a Merc tangent for some reason when I was sleeping? I'm running a Yami, but will raise the engine a notch this week and will run this w/e, will let you know the results.
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  #19  
Old 03-03-2009, 08:53 AM
Fr. Frank Fr. Frank is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

Quote:
Did you guys go off on a Merc tangent for some reason when I was sleeping?
Nah. That was about gear ratios, regardless of make.
__________________
Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.

Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!

Currently without a SeaCraft
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury
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  #20  
Old 03-03-2009, 09:23 PM
NoBones NoBones is offline
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Default Re: Performance on a 20cc with a 200 Yamaha ox66

Quote:
Did you guys go off on a Merc tangent for some reason when I was sleeping?
Well you know the old saying...
Once you go black... ..agh, never mind.

See ya, Ken
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