I have recently purchased a 78 mercury 80hp 4 cyl and the previous owner had given up on it after doing a ring job and impeller and never being able to get it to idle. just before he gave up on it he took it to the shop and they gave him an $1100 estimate on replacing all electrical parts and a main bearing. being the motor didn't make any noise when run the only way i can figure they could tell is that the stator may have been getting rubbed by the flywheel and that would be the upper and lower main. Has anyone changed the upper and lower main bearings in one of theese motors and how could I check them?? Also is there any speacial tools needed??<br />Thanks,<br />Chris
<br /><br />The problem with replacing the upper or lower main is that you have to split the case to allow enough slack to remove the end caps. That's one reason for the high estimate. As far as replacing the entire ignition system, that motor obviously isn't worth it, even overhauled. They should find the part that has failed and replace that. Used parts can be found if new ones are unavailable, but most shops won't invest the time to find them. If the bearings are bad, you can usually hear it.