Vibration @ no-wake speed?

[jcoomer]

I bought a used 1999 Suntracker 30' Party Cruiser pontoon boat w/a 1999 Mercury ELPTO 115hp inline four cylinder w/an aluminum prop on it. The motor serial number is OG924658 and says max RPM are 5250. The vibrations are rather severe at the no-wake speed but seem to disappear as I increase the speed. The prop appears to be OK with no visible damage to the eye (the paint is still 100%). The shaft appears to be OK when I spin it by hand and it doesn't have any play in it. It is my intention to purchase a SS prop for it but am not ready to spend $300 on a new prop if there is a shaft problem that I need to resolve first. Any input is greatly appreciated by this novice boater.<br />Thanks!

 

[Beernutz]

Re: Vibration @ no-wake speed?

You might be dropping a cylinder at low RPMs.<br /><br />Try pulling sparkplug wires one at a time while running slow. If you find one that doesn't change the running characteristics of the motor, you've found it. Try changing the plug first. From there, it can go anywhere.<br /><br />Oh, yeah, be careful pulling those wires. Make sure they're loosened up first, and insulate yourself from the connector. They can give you a pretty good blast of juice. If it gets ya, it won't take ya long to look at it!

 

[skier]

Re: Vibration @ no-wake speed?

Remember that with that motor, below 2200rpm's it is only running on the top two cylinders.<br /><br />Craig