RPM's reading high

[Lager]

I just bought this 90 equipped with the 3.0 and the tachometer is reading a bit high. It has the original gauges that it came with and the tach works, just reads about 500 -750 rpms high and something the gauge flickers higher when the engine has not changed RPM's. I Have not had the boat out into the water yet, but I asked the seller what rpms he was hitting at WOT and he told me 5500. I know this is high for this engine, but it has a 19 pitch 3 blade and I doubt this old heap will hit that RPM honestly, thus me thinking the tach is off.
Can anyone think of anything that would cause a tach to be off that much off other then a defective instrument? Cause I sure cant.

 

[Mischief Managed]

Re: RPM's reading high

Just smack it, guessing it's a Faria gauge. They are known for that and a decent knuckle rap or two will "fix" it.

 

[Scott Danforth]

Re: RPM's reading high

most of the marine tachs are multi-engine tachs with a few switches and an adjustment pot.

they are also one of the least accurate gauges on the dash

my guess is that the switch on the back is set to 6 cylinder and he was at 3667 RPM

 

[Lager]

Re: RPM's reading high

Thanks Scott D, guess I need to crawl up under the dash and see whats up. Thanks!
I got a good laugh out of the "just wack it " post. After a look see, I will give it a try.

 

[Lager]

Re: RPM's reading high

Scott D, Winner Winner Chicken dinner.
Thats just what it was, you just saved me the price of a new tachometer.
The tach now reads @ 800 RPM at idle just like it should.
My next question is, why did the original owner not question this?

 

[thumpar]

Re: RPM's reading high

Scott D, Winner Winner Chicken dinner.
Thats just what it was, you just saved me the price of a new tachometer.
The tach now reads @ 800 RPM at idle just like it should.
My next question is, why did the original owner not question this?

A lot of boat owners just run it till it breaks.