Hello - I am looking to re-power a 1983 50' Gibson hb. It currently has two 4cyl 138HP volvo "anchors". The boat is in Boston and I'd like to install engines have the hp to get me from marina to marina in the Massachusetts bay quickly if the weather kicks up as well as not have to fight the windage of the boat when maneuvering around the marina. I've got call into the manufacturer but documentation is scarce. Question: will replacing the two 600lb 4cyls with two 900lb 6 cyls be too much weight or pressure on the transom? Does this sound like a good idea? If I new the cruising or top speed of the boat when healthy I'd have a better idea of the necessity of replacing the existing engines but I know nothing. Any help appreciated. I'm happy to be a new member of this forum. Thanks, Jim