Mid and Lower unit swap, '74 650 to '71 650?

[jahughes]

Have looked around and not found an answer, can anyone tell me if they know, or where to find the answer to whether or not I can take the mid-section and lower unit from a 1974 Merc 650 and bolt it onto a 1971 650 top end?<br /><br />I have a 1971 650 that's got a trashed mid section (guy beat it half to pieces with a sledge to get a corroded-bolt L/U off it before he thought of using a torch) and no L/U, and I have a chance to pick up a complete '74 with a bad powerhead for relatively cheap, but will they mate???<br /><br />From what I can find, the '74 is a 3 cyl, and the '71 is a 4 cyl, don't know if that matters as far as mating up, shaft length, any of that...<br /><br />Thanks all for any info, and keep up the great work on the forums, this place rocks!<br /><br />Jason

 

[WillyBWright]

Re: Mid and Lower unit swap, '74 650 to '71 650?

The gearcase for the 4 cylinder is definaletly different than the one for the 3. Nothing but the sparkplugs will exchange on those outboards. Only a gearcase from a triple will fit a triple. There were 50 triples (I've only seen 1), 60, 650, and 70. I can't give you an exact year range, but the mid 70s thru the mid 80s. The gearcases on the smaller twin and 4-cyl models (35-50) look very much the same as yours, but won't fit. The bolt pattern is ever so slightly different.

 

[jahughes]

Re: Mid and Lower unit swap, '74 650 to '71 650?

Thanks Willy, appreciate the info! --Jason