67 larson 17.5 outboard swap??

[jesballs57]

hi <br /><br />i have a 1967 larson 17 1/2 feet long, with a same year 80 hp rude(goes 30 mph top speed).id like to swap it for a four stroke. the tag on the boat says it will handle up to a 120 hp.my question is will it handle a 115 four stroke or will the wieght be too much for it?are those old outboards that much lighter than the newer 4 strokes?also how about down sizing?would there be that much proformance loss?... boat is used for fishing in fresh water and in the san francisco bay