I know little about I/O's so I will not comment on the performance ofthem.
As for the bracket addition, I think It would be a winning solution for you
1: Much more cockpit space
2: Props are running in cleaner water
3: IMO outboards are more desirable for resale (not that you would ever sell a classicseacraft [img]images/icons/wink.gif[/img] )
I have seen a few bracketed 23's and all the owners were pleased. power combos ranged from single 200's to twin 200's with the full spectrum between. The only one that I saw that looked a tad scarey was a 23 I/O to bracketed ourboard conversion but they used a non-floatation bracket and put twin 200's on it. At rest the boat looked a tad "off Balance" I imagine at speed the running angle probably helped but at rest the boat was very stern heavy. Point being go with a floatation bracket.( I am sure that was your plan anyhow)
Considering this 23 had twin 200's with a non-floatation bracket I think 200's would work and that is a lot of ponies behind a 23 foot boat. Granted you may have to stay within Manf. suggested limit for insurance/safety concerns.
Here is a pic of a 23 on Boattraderonline with a set of V6 yamahas
Anyone know who the outfit is that is selling this boat? They have this one and a 20 in amazing condition, all tricked out with teak decks and brackets etc. Curious if anyone knew them?