70 HP / 20 Sl Power Question

Poppy21

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I just bought my 2012 Bennington 20sl with a 70 HP Yamaha. I took it out the other day for the first time with 7 passengers and it only ran 13 knots.Today I took it out by myself and it ran 16 knots with adjusted trim. The only problem I could see it that it only got to 4400 rpm at full throttle. I'm thinking I should at least see 5500 Rpm safely. Could it be possible that I need to get the throttle adjusted? Is the normal for a 70 hp? Any suggestions?
 

goldnrod24

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Probably propped wrong. In order to know for sure, get a GPS verified speed and determine the prop diameter and pitch. Post it here and maybe we can help. You should also look up the max rpms for your motor. I'll bet it's higher than 5500.

I am moving this post to the "Props and Power" sub-section.
 

Steve21slx

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Check your intake. On my 2016 90 HP yamaha the part that surrounds the intake warped and caused the motor to starve for air. Couldn't get it to run above 4000 RPM. Not sure if that is your issue but it is one you can easily check off.
 

Poppy21

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Probably propped wrong. In order to know for sure, get a GPS verified speed and determine the prop diameter and pitch. Post it here and maybe we can help. You should also look up the max rpms for your motor. I'll bet it's higher than 5500.

I am moving this post to the "Props and Power" sub-section.
Thanks. Never thought about the prop size.
 

SEMPERFI8387

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2young2retire

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I have the same boat with a t50 motor and had the exact same problem. Approx 4400 RPM with just the wife and I at 18 MPH. When pulling the grandkids in a tube the RPM dropped to 4000. Went to The Hull Truth forum and asked for recommendations. I was running a 14
x11 prop and what was recommended to me was a 14X9. Made the change and now very happy. WOT is now around 5500 RPM and the speed increased to 19/20 MPH. Only about 200 RPM drop when pulling the kids. Very happy now.

 
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