Tach seems off

[JoshOnt]

So new boat, took it out on Sunday and max rpm I got was 4100ish, I looked on the prop to see markings and I can't seem to find any. The prop is in okay shape but could use replacing in the spring. The boat is a 1977 crestliner 550 witha 85hp merc on the back. Any advice on getting the rpm up to speed?

 

[64osby]

Do you know what the max rpm is for your motor?

 

[JoshOnt]

Do you know what the max rpm is for your motor?

5000-5500 is what I have found.

 

[64osby]

Have you checked the compression? Done a drop cylinder test?

Sounds like you may a weak cylinder or running on 3.

 

[JoshOnt]

Have you checked the compression? Done a drop cylinder test?

Sounds like you may a weak cylinder or running on 3.

No but I will, also the fact you even think of that before the tach being the issue worries me a lot since I can't do work on the motor.

 

[JoshOnt]

How would I go about testing the accuracy of the tach?

 

[64osby]

Hooking the motor up to a known good tach. You can buy a "Tiny Tach" pretty cheap and use it.