Driveshaft size?

[EHardgrave]

I have a 1979 7.5 merc. (s/n 5343319). I wanted to be sure I got the right imeller for it. I see there are 2 different sizes of shafts for this hp motor. Any ideas from the S/N what size mine is? I don't own a micrometer.

 

[rickdb1boat]

Re: Driveshaft size?

Well, not real scientific, but .4375 equals 7/16". This is real close to the one that measures .438.(Smaller one) Maybe you could come up with a measurement that would tell you which one you have from this.(Like see if a 7/16 open end wrench will just about slip over it) Hopefully others will just know the correct one. Might just pull it off and take it to a car repair shop and have them measure it. A place that does brakes would be even better..

 

[EHardgrave]

Re: Driveshaft size?

Thanks I will try that.