SUPER SPORT 15 with Yamaha F70: Pull Water Skier

Optimizing the performance of Boston Whaler boats
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Joined: Tue Sep 14, 2021 7:56 pm

SUPER SPORT 15 with Yamaha F70: Pull Water Skier

Postby sbieker » Tue Sep 14, 2021 7:58 pm

Will a [Yamaha] F70 [on a SUPER SPORT 15 hull] provide enough power to pull a water-skier?

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Location: Michigan, Lower Peninsula

Re: SUPER SPORT 15 with Yamaha F70: Pull Water Skier

Postby jimh » Wed Sep 15, 2021 5:22 pm

I suspect the performance in pulling up a water skier with a SPORT 15 hull with a 70-HP four-stroke-power-cycle engine will depend on many variables, including:

  • the weight of the water skier
  • getting up on two skis or one ski
  • weight of crew in the boat
  • propeller in use
  • point of attachment of ski tow rope to hull
  • proper engine trim at start
  • proper handling of throttle position during acceleration

The 15-foot hull is a very excellent small boat, but it is not particularly designed for use in water skiing. I have seen a 13-foot Boston Whaler with a 35-HP engine pull up water skiers on two skis whose body weight was not more than perhaps 130-lbs. On that basis I would expect that a 15-footer with 70-HP should be able to pull up a similar load.

Choice of the propeller configuration will also be a big influence. For pulling up a water skier the propeller pitch may need to be changed to be lower than usual, and the number of blades may need to be increased for better results in accelerating under heavy loads.

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Re: SUPER SPORT 15 with Yamaha F70: Pull Water Skier

Postby dtmackey » Thu Sep 16, 2021 1:12 pm

All the points Jim raised will factor into the performance. Let me share my experience based on having the same boat and running it with a 2 stroke and 4 stroke Yamaha 70.

With the Yamaha 2 stroke 70hp and stwainless 17" prop, the hole shot is much better since 2 strokes are know for having plenty of torque in the lower RPM range. We could pull tubes and other water toys with no effort and it would quickly get the boat onto a plane.

With the Yamaha 4 stroke F70 and stainless 17" prop, the hole shot is significanly "softer" as 4 strokes are known for lacking a similar torque curve of the 2 stroke. Top speed is about the same between both motors. We towed this summer with the F70 and it surprised me how slow the boat was to plane off. Next time we pull any water toys, I will drop down to a 15" prop.

Your best chance of pulling a skier is if they start with 2 skis and drop one once they are up.