my ten foot jon boat has a max hp rating of 3 hp.  I was wondering if it would hurt at all to go to a 4, 4.5 or even a 5 hp motor on it I realize to go slower on turns and also it will be a bit heavier but you know.

Being that you are from Canada and I am from Florida I cant help if this is a legal question.  But if the question is will it physically work?  Yes.  

Going over on HP by the amounts you are talking about should improve your performance.  When the stern of the boat sits with hardly any freeboard above water then you have too much HP.

Your concern must be weight. Combine that with you will be Illegal. Id say get a 5 at most, put smaller stickers on it.

where i am it isn't illeagle.  but I was also wondering about just going straight electric.  how much thrust should i get i have a 28 that I got from the neighbourhood garbage when I was out one night and it pushes it ok but not really that fast take forever to get to where I need to go.

It might void your insurance and you might not pass a boat check.

Even the best trolling motor will not equal a 2hp gas engine.  Get the gas engine if you need to go more than a mile.