Maybe an O/B is a good addition for other reasons?
I don't sail in the Pacific North-Wet. I sail in Florida. Sand, maybe some silt on the bottoms around the Tampa Bay area. If I have to deal with coral I'm not going to be as happy, I 'spect.
I have "upgraded" to a C-30 w/ an A4 from an E-25 with an 8HP Nissan.
Now, let me tell you what I think and you can decide whether I'm thinking straight or going off... ahem... half-cocked:
My C-30 has the full fin keel-- so I need 5'3" of water to float. My E-25 had a full keel too, needing 3'10" of water underneath it. My E-25 found the bottom more times than I care to admit, but, unlike the C-30, never needed to be towed off. I will *always* make sure I have some kind of towing coverage, at least here in Florida.
Why was I able to get off the bottom with my E-25?
Because the O/B can "vector" thrust and rotate the boat around the keel so it is pointing towards slightly deeper water.
Oh, yeah, this'd be useless if the bottom was stickier and I had a winged keel, but, hey, for some conditions, I really wish I had a reasonable mounting for a "reasonable" O/B that would be useful on the sailboat (when I don't need the "full grunt" of the inboard engine, for instance, or when I want a lighter touch) yet not too big for, say, a dinghy.
(laughs)
Mind you, I'd love to be able to have a swim platform, too, but, let's be realistic, here.
I would not want to write off the inboard given the sheer grunt it can apply but there are times I'd like to combine it with an outboard's ability to vector thrust w/o depending on the rudder.
So... my vote?
I'd want both.
Well, when I fantasize, I fantasize *big*.
I recognize the downside to the O/B... you need it to burn straight gasoline rather than the gasoline/oil mixture the 2-strokes use. (Do any 2strokes engines use oil injection yet? My brother had a Yamaha RD350 back in the early seventies that injected oil so there was no pre-mixing.) If you have both an inboard *and* an outboard, you want commonality of fuel supplies to make such a project "workable". (I'll leave the irritation of having a diesel inboard w/ the lamentations of not having a diesel engine in the outboard... though a jet engine burns the same variety of fuel, don't it?)
Now, admittedly, I've overhauled automobile engines (no, you don't want to hear me whining about how much I hate GM)... and personally want to scrounge up a re-buildable A4 that I could work on and then drop into my C-30 without taking a long outage.
But, hey, I'm a rag man at heart and *really* prefer to "stay on the rag" as long as possible... or get onto the rag ASAP on leaving the slip. An outboard, in good conditions, is adequate... and can be used for other jobs. (And, no, I would not use one to stir a jacuzzi.)
At best, though, I see an O/B as a kicker. I do *not* see it as a replacement for an inboard.