When you say older engines, how old? My -12 is a 2010 model so the engine is about the same age I'm assuming. The current OP sender is a Honeywell type, would that be the pipe threaded style? I'll take it to my hardware store and see if it threads into a 1/8 pipe fitting I guess that would be my next thing to try...don't want to strip out any threads on the engine ...