There are two GUARDIAN 22 boats I know of that have twin engines. I think they both have older two-stroke-power-cycle engines. Two older two-stroke engines would have a total weight of more than 600-lbs.
In an archived discussion about maximum transom weight, still available at
MAXIMUM TRANSOM WEIGHThttp://continuouswave.com/ubb/Forum4/HTML/002449.htmlI mentioned that the GUARDIAN 22 hull was rated for 720-lbs maximum transom weight in a 2004 catalogue from the Commercial and Government Products (CGP) division of Boston Whaler.
On the basis of the two boats working well with twin engines of more than 600-lbs, and on the basis of the CGP literature allowing 720-lbs, I don't think the HONDA 225 engine you are considering at 600-lbs is going to be too much weight on the transom of a GUARDIAN 22.
Of course, a 600-lbs engine will be a lot more weight than is on the transom now, so you should anticipate that the static trim will be affected. Since you mention bait and bait tanks, I assume you will be angling from the boat and perhaps trolling. Lower trim at transom may allow some water to came aboard over the top of the transom.
Does your particular GUARDIAN 22 have the full-width splashwell that runs across the whole cockpit?
Or does it have the smaller "sink" style splashwell just in the center section of the transom?
Before I would change the location of the center console and the leaning post, I would first move the batteries out of the transom and to the console. That ought to get at least 50-lbs and perhaps as much as 120-lbs out of the transom.
Your present engine probably has a remote oil tank, and that weight will be eliminated with a new Honda 225.