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Author Topic:   lower unit swap
BQUICK posted 01-10-2003 05:00 PM ET (US)   Profile for BQUICK   Send Email to BQUICK  
Does anyone know if a lower unit from a 1970 50 Merc will go on a 1974 50 Merc? The 74 has a big chunk out of the cavitation plate and a dead water pump so I wanted to swap. Splines the same? Gear ratio the same? Shifter shaft?


Clark Roberts posted 01-12-2003 08:05 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Quick, I think they are same but you can determine by side by side comparison/measurements and ratio can be determined by rotating drive shaft and carefully counting the turns necessary to spin the prop shaft one turn. If it take two drive shaft turns for one prop shaft turn then ratio is 2:1.... etc... Happy Whalin'.. clark ... SCN
Bigshot posted 01-13-2003 09:26 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Ratio should be the same but check the splines and shift shaft. The newer one might have SS shafts which the 1970 did not.
BQUICK posted 01-13-2003 05:08 PM ET (US)     Profile for BQUICK  Send Email to BQUICK     
Are the stainless and non-SS interchangable?
Bigshot posted 01-13-2003 05:19 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Yup. We did a 1972 9.8 with a 1983 foot and it bolted right up.
BQUICK posted 01-14-2003 03:31 PM ET (US)     Profile for BQUICK  Send Email to BQUICK     
Stainless is good! My original 70 shaft was reg. steel and it was half as thick (from corroision) as it was originally....I guess from all those dunkings coming off plane with 15 in. lower unit.


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