The engine and outdrive wiegh 653 lbs total the 135 optimax wieght is 431 lbs, plus a bracket, 100 lbs maybe, I don't know, so 531 approx for optimax means there is about *122lbs difference in weight, adjust the with the fact that it sits 4 feet further forward (ballpark) and you would need to carry 50% percent of the fuel to get the same range....does not seem like much of a difference to me...whatcha think?
As far as price goes, if someone were to buy a new motor and a bracket and do the transom mods required. The cost would be real close to the same amount as the bolt in diesel, the price seems reasonable especially if you factor in getting a 100% increase range.