Speed problems on pontoon

[Riznsun73]

I have a 2007 Bently 20 foot pontoon I bought used with no motor so I bought a 85 hp evinrude installed it with a shaft extension the pontoon could reach a speed of 20 mph no bad bought I just put a 115 evinrude on it and a shaft extension and I still only getting 20 mph the outbound came of of a 24 foot pont getting 22 mph what can I do to achieve 22mph or better the reason for the shaft extension I was gave ventilation issue with both outboards at 16 mph the boat speed stalled and the engine sounded like it was reving up even though it wasn't so the shat extension solved that now just need more speed to knee board any advice?

 

[oldboat1]

It sounds like you are fretting over an extra 2 mph. Try putting more weight up front -- see if that makes the difference.

 

[racerone]

Model # of the 85 HP?-----Perhaps not prop rated.-----Model # off the 115 HP ?------Is the 115 confirmed to be in good condition ?

 

[Riznsun73]

Took me a little bit work has me straped but motor model e115tslecm motor works great just I would have thought a little more speed since that same motor was producing 22 on a different pontoon also I'm running a quicksilver black diamond qa2206x 17p