I upgraded an older 40 hp 4 stroke to a 90 hp Optimax with no issues on my 18' Tracker pontoon, (my insurer, progressive had no issues with it and didn't increase my deductible or raise my policy rate). Remember your talking about doubling the hp and adding additional weight, both of which puts more stress on the transom. You should do the same as I, and look everything over well, ensuring all welds are solid with no cracking or corrosion. I have no regrets with my upgrade, the pontoon performs better, goes fastener, uses less fuel cruising and is more reliable than before. About every six months I pull it from the water and inspect everything, logs, transom welds, etc... if you have kids and plan to pull skiers and or towable's, you will not be disappointed with the upgrade.