My 1gm tachometer is slow / sluggish to respond to throttle settings. Is it the tachometer which is 16 years old or the tachometer sensor/ sender?
Yanmar 1gm questions
- Thread starter Gerry DELICH
- Start date
Welcome to SBO.
The first, easiest and cheapest fix is to track down and clean the terminals on the tach and the sender.
The first, easiest and cheapest fix is to track down and clean the terminals on the tach and the sender.
Here is the print on how it works..Note that the tachometer instrument itself is notoriously inaccurate.. mine reads 2000 when the optical tach reads 2800. There are options available from a few instrument guys like VDO etc.. The ones that are usable are programmable to accept the output from the "tooth reader" on the flywheel.
While the tach on the 1GM is inaccurate, yours is wildly off, which suggest something is wrong with it. On both the 1GM in my boat as well as the spare sitting in my garage, the tach can be off by as much as ~250 rpm. The error is not consistent or linear across the rpm range. It is most accurate at the very low and high ends, with various amounts of error at different rpm in between. Wherever it is off it reads too low.
I made a deviation table for the tachs on both engines and they were very comparable with one another. This suggests to me that the 800 rpm deviation you are seeing points to something else being wrong.
Of course, my engine is a 1GM and I'm not sure what Yanmar you have. But still, 800 rpm is an awful lot and I doubt that can be right even by Yanmar standards.
The Yanmar Tach is basically an AC volt meter. The sensor creates an alternating current as the teeth fly by. If the tach is reading too low it is because the voltage reaching it is too low. That can be caused by poor connections at either end or degrading wire between them.
The tach on my 3JH2e won't read below ~1500 rpm and after that it seems pretty accurate, based on engine sound and boat speed.
Try cleaning the contacts or replacing the connectors. When I replaced the connectors to the sensor, the tach went from not working to working at higher RPMs. Next up is to replace the contacts on the Tach end.
The tach on my 3JH2e won't read below ~1500 rpm and after that it seems pretty accurate, based on engine sound and boat speed.
Try cleaning the contacts or replacing the connectors. When I replaced the connectors to the sensor, the tach went from not working to working at higher RPMs. Next up is to replace the contacts on the Tach end.