Re: pontoon?????
As stated, I wouldn't try it in an 18 with a 25 horse but on a bigger boat with real power absolutely.
A company was running and ad last year and went from Navy peir to Macinac Island in a toon and we sell alot of boats on Lake of the Ozarks which is a giant inland lake that is notorious for bad water.
I would look at a 25 tri in either OB or I/O, even a 22 with 25'' tubes would do fine and at least 150 horse.