Re: horsepower increase
You're right there are some series of outboards where the manufacturer produced the lower HP motor by simply using a smaller carb (1980s Merc 18/25, 1974+ OMC 9.9/15). However, I'm guessing you have a 60hp triple. Those triples are some of the most highly-tuned (hp/cubic inch) motors OMC made. Perfectly reliable if in good mechanical shape, but more sensitive to being off tune, and easier to then burn out (particularly the middle cylinder and/or exhaust jacket leaks). Lots of service bulletins recommending jetting richer, slight retard in timing, etc.. Yeah they made the 1986+ 70hp with the same displacement, but I'd be happy I had the 60. <br /><br />OK, that said, there's lots you can check in your setup to gain some top end (potentially). You want the motor as high on the transom as you can get, without cavitating on turns or losing water pressure. You can keep an eye on water pressure with a gauge, or just run a tube (temporarily) up to where you can see it, and watch the outflow. Once you find the right height, then you want to prop so you hit 5800-6000 with your lightest load (just you alone in the boat). A good, non-dinged up prop can make a big difference, & stainless ones are generally more efficient because the blades can be thinner. <br /><br />Goes without saying to check your WOT timing, compression, and general motor condition. Is there some reason to belive the motor isn't putting out full power/speed, at present?
