Evinrude Vibration Problem

[roswellric]

93 Evinrude 115 hp V-4, new Powerhead, plugs, wires & prop too. The motor seems to idle OK.<br /><br />The motor will turn 5200-5300 RPM at WOT and runs just fine. When turning under 4500 RPM the vibration is intermittent - every 10-20 seconds apart . I put my hand on the top of the motor when it was doing the vibration and could definitely feel it vibrate. In fact I can see the vibration in a table in the stern. <br /><br />The shop that put the powerhead on keeps approaching it as an ignition problem (plugs, wires etc) but nothing changes. When I stare at the tach when the vibration starts and ends I see no discernable change in RPM. <br /> <br />Oh yes, during break-in of the new powerhead a freeze plug blew out which really made the motor stumble. I first thought all the extra break-in oil had fouled the plugs but when I pulled the cover and started it up water went everywhere. Could this have overheated one of the cylinders and I have a compression problem??

 

[Walker]

Re: Evinrude Vibration Problem

Freeze Plug??????

 

[Solittle]

Re: Evinrude Vibration Problem

Check the compression but also check for a good strong bright blue snap at each spark plug jumping around a 1/4" gap.

 

[R.Johnson]

Re: Evinrude Vibration Problem

Any engine will reach a point in it's RPM range called harmonic imbalance. You can see this point quite easily if you point a timing light at the flywheel. It will appear to ripple, or move in waves, and the engine will vibrate. Without being there to listen to it, I wonder if you are running at this point. I am certainly not discounting a fuel, or ignition problem here. If it should prove to be imbalance, don't hold the engine at that point.

 

[Dhadley]

Re: Evinrude Vibration Problem

If it didnt do it before, it shouldnt do it now. Unless they backed off the timing or rejetted or rebuilt the prop or otherwise changed anything. If they backed off the timing it could be that its just too rich for the spark advance at that rpm.<br /><br />Make sure the right Champion plugs are in it and everything is correct as far as sync & link goes.<br /><br />BTW -- 5200-5300 is lugging the motor and will lead to a relatively short life. Why was it rebuilt? Broken rings on the starboard side?<br /><br />And -- quoting Walker -- what freeze plug??????