I have a 1992 Mariner 90hp engine 3 cylinders. Just bought it. At 15-18mph it runs at 4000 to 4200 RPMs. Seems high to me, is it? Also, what are some easy and cheap things I can do to improve engine performance? Spark plugs are new.
Throttle wasn't wide open because I was scared to do some damage first time out with the boat. I think my gauge only goes to 5500. How do I test for a slipping prop hub?
Mark a line through the hub so you can clearly see if there is any separation of the line and with the boat in the water open it up to WOT in forward. Bring it back onshore and see if the line has separated. if it has, you then know that the prop has spun in the hub.
