Tach problem

[Steve Johnson]

I noticed a few times when starting the engine, the tach would spike
over to the far right, over 4000 rpm, and stay there. After a few
minutes it would come back down to a reasonable reading. The last two
trips of about three hours each, it never came down. Just stayed
maxed out to the right until I turned the engine off. Then it came
back down to zero.

Any idea where I should start?

Thank you.

Steve Johnson
Grand Rapids, MI
'82 FC35