1999 22' with a 100hp Yamaha - Speed?

texas_jarod

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Hey everyone, this is my first post. I just bought a 99' Bennington 2275 with a 2001 yamaha 4-stroke 100hp motor. It's such an odd size motor, but I'm running 23mph with 2 people, bimini top up, and a light load. It's only running 4800-5100 RPM. Do I have room to run higher RPM with a faster prop on an older motor, or should I just be happy with the performance? I'm not disappointed, but could use the extra power with more people on board.
 

2fast4u

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those rpms seem low. I turn my 115 yam 5800 to 6000 rpms sounde ki
like you are way over propped each prop pitch usually adds 250 to 300 rpms I would think 5600 should be ok on that motor. Also be sure your toons are clean, dirty toons can cause you rpm and speed loss easly.
 

texas_jarod

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those rpms seem low. I turn my 115 yam 5800 to 6000 rpms sounde ki
like you are way over propped each prop pitch usually adds 250 to 300 rpms I would think 5600 should be ok on that motor. Also be sure your toons are clean, dirty toons can cause you rpm and speed loss easly.
Toons are squeaky clean. I suspected that... I'll pull it off this weekend. So I drop the pitch 2-3 sizes? What's your top speed on the 115?
 

Titletown Mike

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Texas_Jarod, just remember there is a balance between hole shot (how quickly you get up to plane or ability to move from a stand still) and top end speed. If you strictly go for top end speed, it will affect your hole shot. If you go for a good hole shot, you will lose top end speed. If you will generally have more people/weight on board, some would rather have a better hole shot than top end speed as it will seem like it takes forever to get moving. If you will have less people/weight, dropping the pitch will definitely get you some more rpm and top speed. How much more, hard to tell, but with a 100 hp motor, likely not more than 2 mph.
 

texas_jarod

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Texas_Jarod, just remember there is a balance between hole shot (how quickly you get up to plane or ability to move from a stand still) and top end speed. If you strictly go for top end speed, it will affect your hole shot. If you go for a good hole shot, you will lose top end speed. If you will generally have more people/weight on board, some would rather have a better hole shot than top end speed as it will seem like it takes forever to get moving. If you will have less people/weight, dropping the pitch will definitely get you some more rpm and top speed. How much more, hard to tell, but with a 100 hp motor, likely not more than 2 mph.
My acceleration is fine. I have very young children, so I am usually easing up the throttle anyways. It would be nice to get over 25mph, but I also heard that being over-propped and running full throttle can be hard on the motor? If that's not the case, I don't want to spend $300 on 2mph. In fact, I don't even want to pull my boat out of the water, lol.
 

Vikingstaff

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It is not good to be over propped and motor running hard at low rpm’s. There is a recommended RPM range for each motor. I would go to the Yamaha website and find out what it is for your particular motor. It is likely in the range (or close to it) of what has been said above. Then do the math on getting a smaller pitched prop (adding about 200-250 rpm for every 1” in pitch size you drop) to increase RPM’s back into recommended range.
 

2fast4u

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Toons are squeaky clean. I suspected that... I'll pull it off this weekend. So I drop the pitch 2-3 sizes? What's your top speed on the 115?
my boat is a gl2250 2 25" toons with a yam 115 top speed 28 mph at 6000 rpms look and see exactly what pitch you are running now, I run a 13 Pitch i suppect a 11 or 10 pitch may be what will work best for you.
 

goldnrod24

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That's a very respectable speed for that combo and if you like the acceleration, I would say, "If it ain't broke, don't fix it."

Save your money for gas. Or beer. ;-)
 

2fast4u

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It is not good to be over propped and motor running hard at low rpm’s. There is a recommended RPM range for each motor. I would go to the Yamaha website and find out what it is for your particular motor. It is likely in the range (or close to it) of what has been said above. Then do the math on getting a smaller pitched prop (adding about 200-250 rpm for every 1” in pitch size you drop) to increase RPM’s back into recommended range.
good advice!
Over propping a boat is one of the most common problems on boat setups .
 

texas_jarod

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Thank you guys for all the replies and information. Here is the crazy update... I took the boat out today.. typical choppy 15mph wind I've been in since I purchased the boat, and it's been consistently 4800-5000 rpm. Today I was topping out at 5600 RPM with 24mph top speed. 18mph cruising speed (4200rpm). I guess the old girl just cleared her lungs after sitting in storage for 18 months. I'm going to enjoy the boat as is until I'm ready to upgrade. I noticed that my old Bennington is still nicer than a lot of newer pontoons. Not bad for $10k! Happy tooning!
 

Remediation

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Could have been old gas.
 

texas_jarod

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That's a really good point. Just got down to 1/4 tank on my first fillup. The last owner didn't know if the radio worked and his only advice was to start it up every week or else the carbs get clogged. He owned it 18 months. lol
 

jmoreland

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I have the same motor on 2575FS and run a Solas 13 pitch 4 blade and really like it a lot. When toons are clean with a full tank of fuel(24 gallons) I can hit 23 on GPS @5,900 rpm’s.
 

texas_jarod

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Ok, so I hit 5600 rpm with my wife and I. Just took about 1100 pounds of people out and topped out at 4800 rpm. Should you be hitting 5000+ rpm with a full load?
 

texas_jarod

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I have the same motor on 2575FS and run a Solas 13 pitch 4 blade and really like it a lot. When toons are clean with a full tank of fuel(24 gallons) I can hit 23 on GPS @5,900 rpm’s.
were you saying you have the 100hp Yamaha 4 stroke? That’s a 25ft boat too right? I’m only having RPM trouble with 4 or more on board.
 

2fast4u

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You need to prop your boat for 6000 rpms with full tank and two people on it. then when you add a few more people 2 to 4 you rpm will drop but not all the way to 4800
 

texas_jarod

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Is a props performance really specific to a boat, or could I order that prop based on us running the same motor on a very similar boat?
 
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