1980 70hp Johnson Lower Unit Compatibility

Hi All,<br /><br />The lower unit on my 1980 70hp Johnson mysteriously burned out and locked up last week. Seems that all of the fluid leaked out in a couple of weeks without me even noticing. I managed to get it off the engine, and since then I've been shopping around for a used or remanufactured lower unit that will fit. How do I know if a particular lower unit that I come across will fit or not? I can't seem to find a reference for this, and my service manual doesn't address the issue. I've come across a number that seem to have the same measurements but I'm afraid there might be internal differences that would cause me problems.<br /><br />Another question - assuming I can find a working replacement, can I just bolt it on, fill it with fluid and head for the lake, or is it more complicated than it seems?<br /><br />Thanks,<br />Mark

Re: 1980 70hp Johnson Lower Unit Compatibility

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Re: 1980 70hp Johnson Lower Unit Compatibility

I believe that the lower units for the omc 60-70hphttp://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=023549, 3 cylinders, are the same from 1978-1998. From 1989-98, the engine's crankshaft was changed and the splines on the driveshaft differ from those before 1989. <br /><br />If you still have the driveshaft off your old motor. You should be able to switch the driveshaft if you find a 1989 and later lower unit. Check out iboats for their selection of lower units or please contact me and I might be able to locate one for you. <br /><br /><br /> northescape@yahoo.ca

Re: 1980 70hp Johnson Lower Unit Compatibility

stinger288 said:

I believe that the lower units for the omc 60-70hphttp://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=023549, 3 cylinders, are the same from 1978-1998. From 1989-98, the engine's crankshaft was changed and the splines on the driveshaft differ from those before 1989. <br /><br />If you still have the driveshaft off your old motor. You should be able to switch the driveshaft if you find a 1989 and later lower unit. Check out iboats for their selection of lower units or please contact me and I might be able to locate one for you. <br /><br /><br /> northescape@yahoo.ca

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I have the same motor the 1980 70hp with the lower unit needing replaced. Found a 1981 60hp lower unit. I've been looking all over the web to see is this unit is compatible. Thanks for any info... hkpayton3@yahoo.com