On Jun 29, 10:28 am, " wrote:
I am using a 3 HP to power my 9foot Achilles inflatable. Would moving
up to a 9.9 Force outboard be too much? The info plate on the
inflatable says 8HP max. I don't plan on anything high speed, just
more power just in case. ...

I suspect that you can get away with that. However, you might want to
consider a couple of issues. First, the boat will be overpowered and
you will want to take care with the handling and keep an eye on the
structure and it will be illegal in most states so keep an eye on the
law as well. Second, I think the Force 9.9 used the same block as the
15 so it will be heavy, a Yamaha 8hp two stroke will be a lot
lighter. Third, two strokes are pretty messy when lightly loaded so
it'll be kind of un-green. In the distant past I had a 9' Achilles
wood floor with a 6hp and it would plane with two adults but was
marginal. If it were my boat and money wasn't the primary issue I'd
put a Yamaha 8 two stroke on it.

-- Tom.