Pulling flywheel--20 hp 1976 Merc, busted bolt in hole

[Motor Boater Bill]

There are two threaded holes on the flywheel, marked and designated for attaching a flywheel puller. However, one of these has a bolt broken off in it. There are six other bolts adjacent to these two holes--however, these are national fine threads where the two designated holes are national coarse threads. My question is, since one of the designated holes is blocked, is there any reason not to use two of the other holes, with the right bolts, of course, to pull the flywheel? I haven't seen the underside of this flywheel yet so I am not sure how these holes might differ as potential pulling points. I am using an automotive type harmonic balancer puller. Thanks!!! <br />------------------------------------------------------------------------

 

[dolluper]

Re: Pulling flywheel--20 hp 1976 Merc, busted bolt in hole

No for the other fine bolts ,the one that,s broken get a drill and a centre punch , centre punch in the middle of the bolt and then drill using a small drill to start then keep stepping up drill sizes until your ALMOST the bolt size ,the bolt now carfully can be chiseled out re-tap threads

 

[DHPMARINE]

Re: Pulling flywheel--20 hp 1976 Merc, busted bolt in hole

The designated bolts are directly opposite each other for an even pull.The other bolts won't work as well.And may also break.<br /><br />DHP

 

[rayjay]

Re: Pulling flywheel--20 hp 1976 Merc, busted bolt in hole

You MAY find that you are able to remove the broken bolt by carefully trying to turn it out by using a sharp chisel or punch and a small hammer . Place the chisel/punch on the edge of the bolt and attempt to tap the bolt in the correct direction to turn it out.<br /><br />Once you get your puller in place if the flywheel seems like it doesn't want to pop off then slowly heat the flywheel boss with a propane torch. By warming up boss it expands and releases from the taper on the crankshaft. You don't want to get the flywheel too hot which is why I only use a propane torch.

 

[Motor Boater Bill]

Re: Pulling flywheel--20 hp 1976 Merc, busted bolt in hole

Thanks to all for your responses. I did end up using two of the other holes, also directly opposite each other and using long bolts with fine threads. The flywheel came off with a bit of pursuasion from an impact wrench on the puller. Here is what I think happened. I learned from another source that all the holes are supposed to be fine thread, so apparently someone threaded coarse thread bolts into the two "pulling" holes, and broke one of them off either putting it in or getting it out. I'm told that the difference between the "pulling" holes and the others is that the other bolts are staked in, and the pulling hole bolts just have lockwashers. I never saw the pulling hole bolts as they were long gone before I got the motor. Anyway, my plan is to put new, fine-thread bolts in my two "new" pulling holes with lockwashers on them so I can continue to use these holes in the future. I have already screwed a bolt into the empty pulling hole (it went in hard, since the treads had already been corrupted). I'll leave the stuck bolt where it is. Again, thanks for the help.