We sail a 1985 Pearson 303 and estimate our Yanmar 13 horse to have roughly 1800 hours on it. A new concern has developed after we have been motoring for a few hours. We normally run between 2500 and 2700 RPM averaging 6 knots in standing water. I normally can throttle up to 3000 to 3200 RPM and get 6.5 but I don't hold that for long. Lately, when I throttle up after running for hours, it will briefly reach 2900 but than bog down to 2600 or so regardless of the maxed throttle. If I sit in our slip allowing the motor to cool before shutting down, I can push it up to 3200. When we are first motoring out for the first few hours, we can do the same.
Engine condition:
Engine condition: