Just came off Lake Folsom in Ca (reservoir). We were cruising strongly at 3200 RPM and 31mph for about 10 minutes on moderately bumpy lake water. Then................
...........Suddenly, the tach went to 5000 RPM (above the 4400 redline) but there was no change in engine performance, boat speed, sounds, or gauges except the tach. No prop cavatation occurred, and the sterndrive was in the fully down position.
I run a 5 blade High 5 stainless prop which will over rev the engine if enough throttle is applied. The throttle position did not change in the above scenario. The prop has been run successfully for about 50 hours. There is a "Stingray dole fin" mounted on the cavatation plate.
While returning to shore, the analog tach would read 4000 RPM in gear at idle, 3800 rpm when cruising at 28 mph, and then about 1600 rpm in neutral. Occasionally it would display 5000 rpm while throttle was applied from a standing start. At no time did the engine sound distressed nor did the other gauges indicate a problem.
This is a 2000, 5.7L mercruiser with an Alpha One Gen II stern drive.
This was the first boat ride since a spun coupler was replaced.
I would think this is a faulty tachometer problem but am searching for a way to identify and then fix the problem. Any help would be appreciated.
Dean
2000 Maxum 2100SR
...........Suddenly, the tach went to 5000 RPM (above the 4400 redline) but there was no change in engine performance, boat speed, sounds, or gauges except the tach. No prop cavatation occurred, and the sterndrive was in the fully down position.
I run a 5 blade High 5 stainless prop which will over rev the engine if enough throttle is applied. The throttle position did not change in the above scenario. The prop has been run successfully for about 50 hours. There is a "Stingray dole fin" mounted on the cavatation plate.
While returning to shore, the analog tach would read 4000 RPM in gear at idle, 3800 rpm when cruising at 28 mph, and then about 1600 rpm in neutral. Occasionally it would display 5000 rpm while throttle was applied from a standing start. At no time did the engine sound distressed nor did the other gauges indicate a problem.
This is a 2000, 5.7L mercruiser with an Alpha One Gen II stern drive.
This was the first boat ride since a spun coupler was replaced.
I would think this is a faulty tachometer problem but am searching for a way to identify and then fix the problem. Any help would be appreciated.
Dean
2000 Maxum 2100SR
