check valves

[check152000]

i was told my 2000 fiche150 had checkvalves that were bad maybe ,cause my motor would only idle at low rpm for 20 min and would be so filled with oil would have a hard time getting onto plane ,,it would clear as rpms rise,, i have trolled this motor for 8hrs on end pulling crankbaits and it never did nothing to the motor,,was harder on plugs for sure but never did this,,,could anyone tell me if this could be my problem,,,,over the yrs maybe lost 5% of speed ,,top end...

[boats.net]

That is very possible.