blazer/bay- 2008 yamaha 150 2 stroke tach reading high

[baybreaker]

my mechanic just rebuilt my carbs and adusted the idle rpms to 700 he said it was idling high ran the boat starting fine but tach read off scale at 45 mpg back at dock idleing it read 1800 rpms turned it off guage went to zero cranked it back up tach went back to 1500 rpms but dosent sound like that many, my mechanic said faulty tach or maybe moisture got in it , needle guage tach,, new one is cheap anyone one else having this issue?

[dc2220fisherman]

I have had this issue also but not on my blazer, my ranger bass boat was doing the same thing, threw a new tach in there and never had a problem since.