You will need to provide a wee bit more information before anyone can answer that honestly. What speed is the tides in the area you intend fishing in..if they are strong tides..then the answer will be no..if not very tidal..then the answer will be yes.
If its round the Firth of Forth in good weather..it should do no problem at all. You will just putter around at displacement speed though.
I have done some major sea adventures with a 2.5hp engine..but I always check there are no strong tides on my route.
This is my 2.5Hp going up Mortimer's Deep..shipping channel on Firth of Forth.. just at half throttle too ..so I speak with experience. Just dont expect to go fast.