Re: repacing distrubutor cap and broke the rotor
Unfortunately, the rotor is integrally cast onto the distributor shaft and is non-replaceable; you have to buy the entire shaft & rotor assy. Not cheap, either!
When you open up the distributor to R&R the rotor/shaft, you'll likely find that the upper & lower bearings need replacing. There's a snap ring which retains the lower bearing; this ring likes to rust and break so best to put a new one in.
Another thing, when you remove the dist shaft be careful not to damage the little electronic pickup (what the "chopper" wheel passes by to trigger the spark), because if you break that, the entire distributor body must be replaced!
You should still be able to get the rotor from Mercury, or try looking up the part on this site. If you can't find it here, check the CDI Ign links at
www.boatfix.com
Use the search feature on this site and you can probably find complete instructions on how to take the dist apart and reassemble. You'll need a flywheel puller if your distributor mounting bolts are tapped into the dist housing vice thru-bolts. If you don't have thru-bolts you have to pull the flywheel to be able to get at all the mounting bolts to remove the dist.
eBay would be a good place to find an entire working used distributor; you can use one from any year of 800-4 or 850-4 from '69 up to sometime in the mid-70's when Merc went to distributorless (ADI) ign on these motors.
HTH & G'luck..........ed
then you would have then known not to try to remove the rotor or it would break. 2 part epoxy might hold for a test. 