Re: Systems Check Tach
No such thing.
The way I read your post, you want the Systems Check functions to work on a 1988 70. Right?
Will not work.
You can use the Systems Check tach as a normal tach with the three colored connections; purple, grey and black, but it will not function with the more modern Systems Check features.
You would have to re-wire, re-fit your whole boat side harness as well as engine harness.
