2009 Mercury 150 EFI-Premixing oil with fuel

My Merc 150 EFI is in very good shape for its age. It has been properly service and maintained since I bought it new. I have always run ethanol free fuel with proper additives (Blue Stabil, Quickleen, Quickcare, etc.), lower unit oil and water pump replaced every year,and on and on. Point is, it is in great shape but getting old, and I need it to last a long time.

Now the question: because of its age, I no longer really trust the oil injection system. Are there any real reasons why I shouldn't remove the oil injection system and just start premixing the oil with the gas like I did for years and years in the past? I realize there is some inconvenience, a little messy sometimes, not "exact, precise" fuel:oil ratio, etc., BUT.....any real major reasons not to premix (other than forgetting to add the oil)? Thanks

NONE, whatsoever. Would not trust oil injection at that age, it COULD be perfect, but if it is not... then what. And there are a lot of then whats with those older EFIs. Just saw one at my mechanics the other day, 150 that oil injection ate it and motor blew up. Otherwise very healthy motor. My mechanic will not warranty an older motor with oil injection still on it if that tells you anything. Only cons are DO NOT FORGET TO MIX (ask me why that's important... ) Pre mixing is a 100% reliable way to make sure your motor is receiving proper oiling. Sounds like with your care to maintenance, if you start premixing that motor'll last a real long time. Remember service injectors sometimes too!

Thanks for the reminder on the injectors.

Thanks for the reminder on the injectors.

If you run at idle for long periods you can expect plug fouling more often. I believe the oil injection is a variable ratio of 100:1 at idle and up to 50:1 at high rpm. Running 50:1 at idle may foul the plugs more often. You will also notice more smoking at idle.