David-
Roger's advice about the using a surveyor if and when you get serious abut the boat is a good one.
My basic gut reaction to an I/O, however, is like this:
1. The I/O uses up a lot of the cockpit space on a boat the size of the 22 or even the 26 or 27 (you don't say which it is).
2. Work on an I/O can be quite expensive, probably more so than on an outboard, and the outboard can be simply be replaced with a new modern 4 stroke engine cheaper than renewing an I/O drive unit and the marinized automotive engine. A 90 hp 4 stoke engine can be had for $8-10 K, where the outdrive and engine will cost at least that much to replace, and will still require using some of the older parts, like the manifolds, water pick-ups, fuel system components, etc.
A few of the older I/O equipped 26/27's have been successfully converted over to outboards, but for a boat that size, a big outboard bracket has to be built, and a 200-225 hp outboard will cost many thousands of dollars more than the 90. You'll also have to plug up the stern and add a new set of controls, gauges, etc. This type of project is not for a person new to boating, generally speaking.
Still, it could be a fun adventure. You need to hear from Haleigh's Comet and Alvig, among others, who have faced this squarely and made this type of decision. Haleigh's Comet was converted over to a 225 hp Honda and bracket by Les at EQ Marine, and Alvig is currently removing his 4 cylinder Volvo to rework himself.
Before you decide to go ahead, develop a very exact budget to be sure it's economically feasible, remembering that boat/marine parts are very expensive and no budget on a project like this can truly anticipate the real final cost due to the unexpected. Joe.