You are only to gain 32kg to go to the Yammie!
Dry Weight 90 Yamaha 126kg - Dry weight 115 Mercury 158kg.
Just sit back and think about this. Rather spend the money on restoring the boat, than to my a swop you will regret later. 32kg's is nothing, put my boerbull in the nose (66kg) and the weight problem is resolved without going through the shlepp of new fitments and costs.