Quote:
Originally Posted by Natural Light Kid
Isn't the rev limiter on a motor typically higher than the "maximum recommended rpm" according to the factory? Is it safe to run a motor at those elevated RPM's, bumping the rev limiter, for an extended period of time?
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I can't speak for all motors. The tohatsu I raced was a stock motor with a rev limiter set at 5800 rpm, we could tack weld the crankshafts to keep them from spinning out of time. Recommended rpm for that motor was 5600, I spun mine up to 7400 rpm for extended periods of time. I ran the Parker Marathon. It is 40 laps of a 4.1 mile course with 1 mandatory 10 minute pit stop. That is 164 miles with one stop at 7400 rpm. The motor would drop down to abut 6500 in the turns then right back to 7400 for the 2 mile straightaway. Ran that motor an entire season with zero failures. On a short course, I would turn up to 7600 by the end of the straights. Most of our races were 1 hour testing on Saturday, 10 lap qualifying heat on Saturday, testing for 1 hour Sunday morning, 30 or 40 laps of a 1 3/8 mile course.
The Merc I just sold was a beast. The original powerhead ran for 10 years. The data showed that I hit the 6250 rev limiter over 400 times. That motor was turning 6200 everywhere I went. After 10 years and 2400 hours, it burned a valve.
The little 2 cylinder OMC 40/50 motors ran a class called sst45. That motor as a fishing motor was recommended to turn 5600, as an sst45, they turned 7200 rpm. They ran the Parker Marathon right alongside me.
I look at the recommended rpm as just that, a recommendation, not a rule.
I have yet to find an outboard that made peak power and torque at the factory recommended rpm. Sure, it might make 50hp at 5600, then it might make 60+hp at 7200.
D