Welcome to the site! What you have is a very rare model of the SeaCraft 23 hull with a fairly common motor on it, so I'd say the boat is a lot more of a keeper than the motor, at least to SeaCraft fanatics! Check out
Moesly SeaCraft and "The Amazing Mr. Moesly" article in Literature Section to gain a good appreciation for SeaCraft's history and evolution!
The 23' hull is one of the best riding boats ever made for it's size. The stringers are fiberglass with a foam core. The core isn't that important (it's the outer fibers of glass that carry the stress), although some foams can retain water and add weight if it gets wet. When Carl Moesly started building the 20' hull with all glass stringers in about 1967, the stringers were hollow and installed about half way through the layup, with more glass laid over them. (See the Boating Magazine article on the 20' Seafari in the Literature section for more details on the layup. After Potter bought the company in late 60's, he eventually changed the 4 stringer design on the 20's to 2 wider box stringers, starting with the 1973 models; don't know at what point they were installed during the layup. Never heard of a problem with either design on the 20's. All the 23's I've seen redone on this site seem to have the 2 wide box stringer design. There have been a couple of 23's and one 25 on here that had part of a stringer pull loose from the hull, but that seems to be very rare, as ALL the Moesly, and most Potter and SeaCraft Industry models seem to be built like tanks; I believe some of the latter models used plywood instead of balsa for deck cores, so they're probably a little heavier than the earlier models. Your model was probably built by SeaCraft Industries; the letters in the HIN/serial number will confim that.