Mercuriser Tach question

[Justaboatin]

I purchased a 1989 18Ft Sylvan with a 4.3L Mercurser. I don't think the tach is working correctly. At full throttle it is only reading 3200RPM I am going 40Mph on a 19P prop. (it sounds much higher than 3200. <br />Question:<br />There is a "dial" thing on the back of the tach, is it possible that the tach is "set" wrong? Are they adjustable to the motor they are setup with?<br /><br />Or do I need to replace that tach? <br /><br />Any advice is helpful

 

[tommays]

Re: Mercuriser Tach question

There should be a 4/6/8 switch on the back <br /><br />tommays