Tach issues.

[merlinroad]

Hi All,   245 explorer wac w/99 225hp johnson
My tach has been acting crazy for some time now (>1 season). It works off and on every time I go out but it has a mind of it own. When I start out i push it up to 4000rpm and its working but when i get on plane it quits or fluctuates between 0 and 4k. If i back off it typically starts working but not always. At wot it never seem to work. I'm trying to determine if its the stator or the tach. The tach is apparently driven off the stator winding. Can i connect an automotive test tach to the back of the gauge to see which item is the problem? If it always works the stator is good otherwise the tach is good. What do you think. Is it a big deal changing the stator, i've been working on auto and mower engines for decades i'm thinkin pulling the fly wheel shouldn't to big a deal.

Thanks
John

[fitz73222]

Do you have a standard OMC control box with the keyswitch integrated in the box. Something could be rubbing the gray tach feed lead causing fluctuations. I had a tach do something similar and it turned out to be the selector switch on the back of the tach that needed to be reseated in its correct mode. Usually if you have a charging system or voltage regulater issue, the tach will not work at all. I suspect a connection issue.

[John Jones]

On my '93 225 Johnson it was the voltage regulator making the tach crazy.  It was not charging properly either.