I have a 9' BPS Pond Prowler that I've been running with a 30lb thrust Minnkota. It can move two people pretty slowly in still water and is seriously underpowered when there is a little bit of current or wind.

I've been thinking about getting an outboard and I will probably purchase a brand new Mercury. However, I do not want to spend money on a motor that is underpowered and then be unable to return it , so ....

Should I go with 3.5 hp, 4hp or 5hp?

The maximum hp rating on my boat is 5 hp.

Do you think that 3.5 hp is enough to move this boat (w/ 2 ppl) in moderate current?

I would go with the max the boat is rated for. You can always throttle back if you are going to fast.

the difference in price between a used 3.5 and 5 hp shouldn't be that much. so I would go for a 5. but yeah I agree with Dougherty go big.   ;D ;D

I would go with the max the boat is rated for. You can always throttle back if you are going to fast.

;D

Years ago I used to hang out at a marine dealership.  A customer brought his new Charger Bass boat back because the thing ran too fast at full throttle, it was scaring him.  He still wanted to jam the throttle all the way down, he just wanted to tune back the carb throttles so they wouldn't open all the way up when he did it.  

yeah go with a 5. i have a 5hp merc on my 12ft jon and it moves pretty good.