Not reaching Full RPMs

[Fisherman]

Have a 2012 E-Tec 115 as a replacement motor and have only achieved 4,200 RPMS at full speed. Replaced all old fuel lines and installed a water separator fuel filter. Accomplished at authorized Evinrude dealer. Thinking it might be the prop preventing top RPMs?

[Joe Reeves]

A mismatched prop would of course limit rpms... or... cause excessive rpms. However, check the compression and spark of all cylinders first. Compression should be roughly in the range of 100 psi and even on all cylinders. The spark, with all s/plugs removed, should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP!

If this engine ever hit its top rated rpm range, you could easily have a clogged high speed jet in one or more carburetors (if a carburetor equipped engine).