I have a Mercury 90 Fourstroke EFI. The engine just recently had a new fuel supply module installed. When I took it for the first run yesterday since having it winterized all season I noticed that the RPMS at WOT were about 1000 more than they were last year at about 6500-7200. Manual says it should be between 5000-6000. The engine ran great, did not sound like it was working any harder than usual and I did not receive any alarms (I have read that the Guardian System shuts power down at 6200 rpms but am not sure). The prop is the one that came with the engine.
I confirmed the pole settings on the back of the tachometer and spun the switch around a few times and put it back to its original settings. At idle it is reading 750 now like the manual says and originally it was reading just over 1000 at idle.
I have also read that the idle is controlled by the ECM so that could indicate to me that the tachometer may just be acting up. I do not have access to a shop tach and can not afford to sink any more money into having diagnostics done after replacing the FSM right now.
Any advice is appreciated, thanks
I confirmed the pole settings on the back of the tachometer and spun the switch around a few times and put it back to its original settings. At idle it is reading 750 now like the manual says and originally it was reading just over 1000 at idle.
I have also read that the idle is controlled by the ECM so that could indicate to me that the tachometer may just be acting up. I do not have access to a shop tach and can not afford to sink any more money into having diagnostics done after replacing the FSM right now.
Any advice is appreciated, thanks
Last edited: