They're telling you to replace every two years? What are these made of, foam rubber? They don't look much different than auto motor mounts. If these are failing that fast I think I'd look around for something of better quality. All they are is rubber valcanized to steel plate. For C$200 with 6 units you could have your own custom made for that price. I have a 50 HP Diesel in my bigger vessel and the motor mounts have been in there since 1981 (6500 hrs.)and I be giving them one more season. They're mostly rusty.
Faithful are the Wounds of a Friend, but the Kisses of the Enemy are Deceitful! ........The measure of a man is how he navigates to a proper shore in the mist of a storm!