Got a oddball application here

I just had a new yamaha 9.9hp four stroke installed on my 16' tracker like bass boat. THe motor was installed by a authorized yamaha dealer. The dealer did a water test and was not able to get above 2500 rpms. They used the prop that came with the motor a 9-1/4 x 9 pitch. The dealer seems to think the motor will not do any more because of the weight of the boat (approx 800 to 900lbs loaded more or less)

Dealer says lowest pitch prop available is an 8 and they thoought that it would not make much difference.

I have seen a number of boats like mine with 9.9 HP on them and I would think that they get more rpms than 2500. The manual says operating range in 4500 to 5500 rpms. Any ideas of what I should do to get a more acceptable rpm reading? Is it possible that the boat weighs too much and the motor is doing all it will do?   I know the boat is underpowered but I went with the 9.9 due to HP restrictions on the lakes I fish.  

Thanks

The motor should turn its maximum RPM no matter how big the boat is, Unless it is really over propped. A 9" prop should not be over propped. I have 9.8 Merc I have put on my 16' Crestliner with a 9" prop it will run 5500 RPM with no problem. It will only go around 6 or 7 MPH though. It sounds like it should go a lot faster.

I would not take delivery until they can get it run the way it is supposed to.