If your old engione was a matriner there is a tiny chance it might fit, however you will need to (probably) at least change the fuel connector to the engine.
HAving said that, I have used an early 90s Evenrude (Johnson) that mated happily with a Yam connector, so when you get the engine, try it & see! That of course assumes your Mariner is (was) a Yam based one and not a Merc "twistlock"
Other thing to check if you need to change the connector is the ID of the fuel hose - its either going to be 1/4" or 3/8".
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