If it's only a few pounds over, it's not going to be an issue, but double check if legally you can have that outboards as it exceeds the mfgrs specs.

Take it from someone who has used it's 12.6 Seaeagle with a 15HP for the last 10 years, go with the largest outboard you can afford and avoid the never ending thought of "what if"

A 20HP would most likely serve your needs also quite nicely if the 25 is out of the question due to the weight issue.

Would you be able to get a 2 stroke instead? There's an internet company selling 25HP Yamahas in the US, that may overcome the weight issue, but it's a 2 stroke...if that's important to you.

good luck!