15 foot duroboat with a 15hp tiller is gonna be sluggish. With those little aluminum boats, you'll want to max out the hp on them, per the manufacturers recommendations. A 15 footer should be able to hold a 25hp or so, I have a little 12 lund aluminum boat with a 15hp two stroke on it, great for pulling pots and puttin' around the sound when its calm and I don't want to put the big boat in.

That 15footer boat is gonna really restrict your fishing from your current boat. It'll be fine on the nice days on the sound, but everyone knows your at the mercy of ma' nature on the ocean and it can change quick. A fifteen foot duroboat is really stretching in for the ocean and

That 12 foot lund I have is great, fill up a 5 gallon tank and run all weekend on it but fishing anything more than two guys isn't much fun.

Instead of stepping down all the way to a little aluminum, maybe consider something like a 16-18 foot center console like a Whaler or an aluminum boat in that size range, hewescraft of alumaweld or something?? Boat like that would be able to handle much more than a 15foot aluminum boat and wouldn't kill your wallet, those boats usually have a 75 or 90 horse on em...