mariner EXTREMLY high tach reading

[ksgoosekillr]

I have a 1991 mariner 90hp, and finally got the tach hooked up and took it out this weekend to get some numbers to give me an idea for a re prop. However at idle i was getting a reading of 1400-1500rpms, and at WOT the needle was buried well over 7k. Anyone have any ideas as to what this is? I dont think that sounds right at all, and my motor deffinately did not sound liek it was wound up that high. as always all help is appreciated thanks

 

[Texasmark]

Re: mariner EXTREMLY high tach reading

Most current tachs operate off ignition impulses from the engine. 2 cycles fire twice as often as 4's. Also, 4's a lot of times are 4, 6 or 8 cylinders. Both can cause measurement errors.

Ensure your tach (on the rear of the housing) is set up for your engine. Sounds like it is not.

Mark