Mongo.. I expect that this reply is far too late to help you, but I will anyway!
I have a Yamaha 150 4 stroke on my 590. There's no doubt that it's heavy, and I have little clearance with my transom... Not that that matters as there is a well there as you know.
If I was doing it all over again, I might re-consider the eTec due to it's lighter weight, but given some of the problems they've had, I would probably do the same thing. I"m going into my 3rd season with this engine, and it has been flawless so far.
I should add that I have a large A-frame and self-righting kit which adds a bit of weight. The frame has two brackets to carry 2 x 25 litre Gerry cans for extended range, although they typically aren't full unless I am going someplace far, far away!