Motor ID Help Please

[ssdvc]

I thought I had an 86 Merc 50hp, but I need to be 100% positive before I do a tune up.

I am trying to ID my "new to me" Mercury. The outboard motor has just one data plate on it and it has one number on, which is A102037. The head has a number on it of 1017-8359, the starter is 50-73521. It is a 4 cyl, 2 Stroke and looks to be in excellent condition.

There is one sticker on the inside and the first line on the top is "M 50"

Can anyone tell me what I am looking at and ID my motor. Before I get this thing in the water I want to tune it up and make sure it runs very well.

Thanks.

[Nos4r2]

Got a pic of it under the cowl?