I recently bought a 1985 18' Sylvan Fish & Ski boat with a '85 Evinrude 90hp V4 mod.# E90TLC0S motor which I understand is a 'Looper' motor but what degree? What designates this motors as either a 60 or 90 degree motor .. how do I tell the difference? .. 'Looper' is referring to what? Wondering also what the general opinion is regarding this motor as good, bad or indifferent. Any particular issues in the history of this motor that I need to be mindful of? Shop manuals are on order. Thanks.