If its the twin pot, weight will be just under 40kg. Handling on a 280 will be 'interesting', floor will probably bulge under the pressure and if you are one up it will be very easy to tip.
Boats have a maximum hp for a reason, exceeding that by nearly double will not end well.
I'm not trying to be a kill joy, I had to stick a 25hp on a 290 last year to get a broken sib and engine back to the launch site. But I was very, very careful and really had no other choice.
I'm sure you will get people telling you that they have done it and it was fine, but IMHO its way over the top.