Ok here's 2 cents worth...
Regulations...
First, understand there is an entire classification (USCG, CFR) for power boats under 2hp. These regulations affect capacity, flotation requirements etc. That being said, your boat is/was more than likely designed within the guidelines of that ruling, which would mean that the boat is designed to operate safely with 2 hp maximum.
Mechanics...
The boat has a very nice length to beam ratio, meaning it that it is much longer than wide. This typically means better performance, and requires less horsepower than a boat the same length, with a much wider beam. That being said, one might think that adding more power would be a good modification. Now in theory, this might be correct, however there are other issues.
First, the shape of the bottom, rising up toward the transom, is excellent for a heavy displacement, slow moving boat, such as a tugboat, riverboat, or push boat. However this shape is definitely not good news if you intend to run "on top". So some might argue that all you would have to do is modify the bottom, and keep it flat all the way to the transom, right? I don't agree, and here's why.
The designers, and marine engineers that spec'd out the material thickness & structure of the boat, did so, with the understanding that the boat was 2hp max. So you could safely assume that the general structure of the hull and internal components, might very well be inadequate for the type of stresses & pressures the hull would encounter, running loaded in a chop for example.
So yes, you could modify the bottom, beef up the structure, change the transom, etc. etc. etc. and possibly end up with a structurally sound "experimental" design. Likewise, you could end up with an expensive headache, and even worse, a dangerous boat.
IMHO, the smart safe move: If you really want to go faster, why don't you pick up a cheap, used, narrow beam jon boat, that is rated for more power, and hang the larger motor on it?
OK that's more than 2 cent's worth, and may not be what you want to hear... BUT your safety, and the safety of your passenger, is ultimately the most important thing
Hopefully you won't shoot the messenger!
