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#1
04-02-2005, 10:21 AM
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New Yamaha 4 stroke numbers
Was it cold...yes, was the rain pelting me...yes, was trying out a new motor awesome...absolutely! My old 1986 merc 2 stroke must have been more tired than I thought, because the new 4 stroke, which isn't supposed to be so quick out of the hole, is a real rocket. The tide and wind were pretty strong but I think these numbers are good. I arrived at the speeds by comparing the GPS speed to the depthfinder speed and taking into account the direction of the current.
Motor: 2005 Yamaha 150 4 stroke 25 " leg (extended transom) Boat: 1986 SeaCraft 20 ft CC (20'6") Carrying: One person, 40 gals fuel Prop: 14x19 2000 rpm 9 mph 2500 rpm 12 mph 3000 rpm 23 mph I haven't gone above 3200 rpm as I am still breaking her in. Between 2500 rpm and 3000 rpm she leaps up on plane.
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'86 20 ft CC with 4-stroke 150 yamaha 
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#3
04-02-2005, 02:01 PM
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Re: New Yamaha 4 stroke numbers
I didn't buy the fuel management gauges so I won't be able to nail down gph but the speed info will be no problem.
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'86 20 ft CC with 4-stroke 150 yamaha
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#4
04-02-2005, 05:50 PM
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Re: New Yamaha 4 stroke numbers
Mark - The Prop calculator should give you a pretty good idea.
http://www.rbbi.com/folders/prop/propcalc.htm Yamaha 150 gear ratio = 2.0 Prop Pitch = 19 With a prop slip of = .149 3000 = 23.0 mph 4000 = 30.6 mph (prop slip 14.9%) 4000 = 32.4 mph (prop slip 10%) ----------------------------------
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#5
04-02-2005, 07:11 PM
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Re: New Yamaha 4 stroke numbers
Whoa! [img]/images/graemlins/shocked.gif[/img] That prop calc says that my slip is only 9%.
20' Seafari, '91 Mercury XR4 w/ large gearcase, 1.68 gear ratio & nosecone, 6150 rpm, 16.5"P PowerTech prop, at 52 mph on the GPS. [img]/images/graemlins/grin.gif[/img]
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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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#6
04-04-2005, 09:28 AM
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Re: New Yamaha 4 stroke numbers
FRFrank.
What size motor is that? 200hp? Abe's Rocket
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1986 Seacraft 23CC etec 250 Portland, Maine
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#7
04-04-2005, 04:06 PM
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Re: New Yamaha 4 stroke numbers
Hat Trick,I have the same boat as yours that I just put a new Evinrude 25" 175 Ficht on last year.I get about 35 knots according to the GPS wide open with a lite load(fuel, people).Not sure the prop numbers offhand.
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#8
04-04-2005, 07:48 PM
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Re: New Yamaha 4 stroke numbers
Bottomline,
My old motor was a 1986 Merc 150 black Max with a 15x17 aluminum prop and I would get 32 mph (gps) at 4500 - 5000 rpm with a 1/2 tank of fuel and two people on board. I don't know what I'll see at those rpm's with the new motor, but I'll let you know when the break in period is over. All I know is that the new motor is peppier at low rpm's.
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'86 20 ft CC with 4-stroke 150 yamaha
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#10
04-07-2005, 07:57 AM
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Re: New Yamaha 4 stroke numbers
I went out yesterday to do some more break in on the new motor. Here are some more numbers:
Motor: 2005 Yamaha 150 4 stroke 25 " leg (extended transom) Boat: 1986 SeaCraft 20 ft CC (20'6") Carrying: One person, 40 gals fuel Prop: 14x19 2000 rpm 9 mph 2500 rpm 12 mph 3000 rpm 23 mph 4000 rpm 32 mph I was only able to get the motor to 4700 rpms at full throttle. That doesn't seem like I'm getting what I should. Do I have the right prop?
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'86 20 ft CC with 4-stroke 150 yamaha
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