I've read somewhere you can convert a 9.9 to a 15 hp by changing the carb is this true and is there any other modifacations required ? by the way I have a 1974 evinrude 9.9 model # 10424s
We've converted them and took 9.9's on trade for the 15. It'll take a pretty special hull design to see any difference. Every time we've done this the customer was unhappy with the time / money vs performance gain. <br /><br />You'll most likely gain more working with the set up.
I certainly can't argue with JB and DHadley about the lack of performance gain, and I agree with their advice that it isn't worth the trouble. But to answer your question, in '74 the only difference was in fact the carb. Block, head, rotating assy, manifold, and exhaust tuner are all the same that particular year. Only the carb and decals are different. I've heard that in later years other parts change.
