Jeff and Enzo:

No, the MC18 DOES NOT have a G.P.S., or even a provision for it.

Enzo, if you have a G.P.S. then I would say the bottom end has probably come from an MC21. How many wires come from the switch? If it has 6, then it's likely to be an MC21 bottom end; if it has less than 6 wires, then it may be an MC28 bottom end. (I think the MC28 has 2 wires, but I'm not 100% on that off hand.)

Please note: this is not a sure-fire way to identify the bottom end. Only the full engine number will tell you that.

Andy.
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