Cat27's are great boats. Love 'em.
4 feet of water is NOT ENOUGH.
You're thin as it is. You add a six pack of coke, a couple of copies of good old boat, a screwdriver and a half a tank of gas, she ain't gonna float in 4 ft. of water. (tall rig)
The shoal draft wing keel is 3 and a half feet draft. If you'd like to chance that last 6 inches, knock yourself out. Just pack light.
I'm going to be very "kind" in the inboard/outboard thing, as well as the gas/diesel thing. (nothing personal)
IB/OB. You're not going to like the cavitation that will result in even with a long shaft OB. period.
You owe it to yourself to take a look at an inboard equipped cat27. There is PLENTY of room to do routine maintenance unless you're 300lbs. (if you are, find a trainable skinny kid)
Prop drag on a C-27 is the least of any worries. This ain't a Melges.
Ok, this has been beat to death.
Find sailboats, not sea-ray, larson, glastron,go-fast or fishing rigs... I said SAILBOAT, that in normal operating order, has blown up due to gasoline. Yes, there are less than 5 that I can find with years full of searching.
Don't use the haul gas in cans as an excuse, unless you're going to refine your own diesel, you'll be hauling that too. (last I heard, some marinas even sell the stuff trust me, you're not going to be buying much)
Diesel stinks. A lot. All the time. Everywhere, For a long time.
Diesel is less lending to do it yourselfers. (fuel, filters, bleeding lines...)
Gas (atomic 4's) have over 40,000 installs, they must have done something right. Parts are available online, maintenance items from your local auto supply. Try getting a diesel injector for a yanmar/universal/volvo at pepboys.
In the light of day, it doesn't matter, gas/diesel, just personal preference.
(as you may tell, I'm an "inboard" guy", nothing against outboards.)
Tiller vs. Wheel. Spend some time on them both. Sit in the cockpit, move the tiller around, a lot.
Do the same thing with the wheel. Stand behind it, quick, grab that jib sheet (with the wife sitting on one side or the other.) Again, its personal preference.
Just don't take preconceived thoughts with you when you look at a potential boat.