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70 HP / 20 Sl Power Question

Discussion in 'Members Zone: Props and Power' started by Poppy21, Aug 14, 2019 at 8:39 PM.

  1. Poppy21

    Poppy21 Member

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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?
     
  2. goldnrod24

    goldnrod24 Moderator

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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.
     
  3. Steve21slx

    Steve21slx Well-Known Member

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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.
     
  4. Poppy21

    Poppy21 Member

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    Thanks. Never thought about the prop size.
     
  5. SEMPERFI8387

    SEMPERFI8387 Moderator

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  6. Poppy21

    Poppy21 Member

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    Thanks. That will work. Looks like I need to change props. I’m trying to get a little more speed so pull the grandkids on a tube. Hopefully I can find the right size so I don’t lose too much low end power when I’m loaded down.
     
    Vikingstaff likes this.

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