CATransplant
Admiral
- Joined
- Feb 26, 2005
- Messages
- 6,319
We're all trying to get our outboards running perfectly. A good tach is the best way to determine RPM, but for older outboards and smaller outboards, that's often not an option, or is too expensive. There's another way to determine RPM, but it takes something of a musical ear to do it. A cheap electronic keyboard is the only tool you need to determine the RPM of your outboard, within a pretty close tolerance.<br /><br />You simply match the overall pitch of your outboard with the closest musical note on the keyboard. The sounds an outboard makes are complex, but there is still a fundamental, dominant pitch to it. <br /><br />Here's a chart showing musical notes and the equivalent RPM your motor is producing. The octave doesn't really matter, since octaves are multiples of the same pitch. So, you can double or half the rpm, to get pretty darned close.<br /><br />This works best for two, four, or eight cylinder engines. It still works for three or six cylinder engines, but the dominant note is not as clear. For lower RPMs than the ones in the chart, it gets a little harder, but you can divide the rpms in the chart by two and figure it out, if you have a good ear.<br /><br /><br />Musical Note to RPM<br />C 1962 or 3924<br />Db 2078 or 4156<br />D 2202 or 4404<br />Eb 2334 or 4668<br />F 2619 or 5238<br />Gb 2775 or 5550<br />G 2940 or 5880<br />Ab 3114 or 6228<br />A 3300 or 6600<br />Bb 3496 or 6992<br />B 3702 or 7404
