Ultimate success! I thought I would provide my experience so to help others, now that I am a **certified Stator replacemnt guy.. More on that later. My project involves a '2000 Johnson 200 HP Ocean Runner/Looper engine. I don't want everyone to expect their application to mimic my spec's but after discussing w/ my 'Real Expert', he describes the puller bolt size for my typical engine size range to be: ?I just use the bolts that came w/ the puller?, and that summary prompts me to believe the size is 'TYPICAL'. (I'm sure his puller is a factory correct OMC tool. My flywheel puller bolt size was actually 8 MM, not 5/16"! I used a standard sized Harmonic Balancer / puller. My ultimately used bolt length was 3.5" but I think as short as 2" would be adequate. Yes the thread size is 'Fine' and grade 8 worked fine w/ no failure. What a collection I now have - (4) 4" 5/16" standard thread, (3) 4" 5/16" fine thread and the correct (3) 3.5" 8MM fine thread. Hey, I only purchased (4) Grade 8 washers!
Flywheel nut size: I will not share the futile frustration this socket procurement endured, to simply share that a 36MM socket bought a Sears was the right tool. Yes the nut size is 1-7/16" but not having to a better ?thin-walled? tool retailer like Snap-on, or otherwise, I unsuccessfully called at least 10 local options to ultimately have Sears success. DO NOT buy the Sears 1-7/16" 3/4" drive w/ a 1/2 to 3/4" drive adapter. The socket wall thickness is gigantic and I can't imagine the others that decided to grind off the excess socket tip material so that it would fit in the MUCH SMALLER flywheel recess diameter! The 36MM worked and fit perfectly.
Here's the last bit of nut removal advice I can share. We tried numerous half-as_ methods to keep the flywheel from spinning to break the nut, all failing miserably. Having **'BUD'S" as a friend, we were able to borrow a 'Flywheel Tool'. We did not try the wedging a bar between one/two of the puller bolts, like I have read as an option by others here, but frankly I think serious damage to the bolts/flywheel puller bolt holes plugged w/ sheared/snapped bolt heads? would occur and I am not sure how the socket breaker bar w/ fit along w/ bar crossed to two of the puller bolts. Everything would be struggling for the small and very limited space. My advise would be that any weekend warrior like me would be best served to get a ?Flywheel Tool? lined up to take on a flywheel removal project on an engine size that my little 200 HP required. (rememberthe nut is torqed to 150 ft #?s. I was lucky to have a friend who lent me one. I am not sure if you can easily rent one or what, but do yourself a favor and just get one. (It looks like a small 'Log Pick' the lumber jacks use. We applied the tool so that the one end was jammed against the starter shroud, and it worked!