OK, I have it now. These ar used to keep the bearing straight as it gets driven in. This is not a Mercruiser tool, it was designed by another. The down side is it works for your current boat, but if you get another boat, the depth may not be the same.
Most don't use that one, because of two issues.
(1) If your motor is not perfectly aligned prior to installing the bearing, the tool can get bound in tight. The bearing goes in, but it will be a real hard to get the tool out. In most cases replacing the bearing will require adjustment.
(2) If you get another boat, the depth may not be the correct depth. Depth is easy enough to fix, just use a piece of heavy wall PVC pipe and block of wood to finish driving it in.
They make other tools which use the alignment tool just over the end
https://www.iboats.com/shop/sierra-...MbaEHFI6YFlzNY34PQGw6NeQVnFAbwhkaAiNLEALw_wcB
Merc parts are
91-37323 Driver Rod
91-32325T Driver Head
91-30366T1 Mandrel Head
I would suggest moving the head closer to the end, so your not going to have the end entering the flywheel. This way you have to keep the bearing centered and perpendicular, but the end of the will not make it into the flywheel.
Before doing it lets see if we can get a couple other opinions
Bondo and
Bt Doctur
