RE: Welcome to Club SAITO !
Tom:
I would suppose Saito switched to steel rockers purely due to the expense, although a flaw in the casting could cause a failure in service; the cast/forged iron/steel rockers would be far less susceptible to such failures.
The wear point isn't the rocker itself, it has the steel pad on the valve end remember, but the rocker pedestals cast as part of the cylinder head. Even there the movement is so slight that wear is only a long term concern. When the pivots do get sloppy a brass busing installation is trivial. When/if you get to that point I can bush them for you, if you don't want to do it in your shop.
Warning about a boat installation: If you put the engine in a "Speed" boat there is the possibility of bouncing the prop out of the water, and if you do the engine rpm will go through the roof. The over-revving leads to valve float, valve float leads to extreme hammering in the valve gear, and that can break a rocker. Please take note.
Sealed or shielded bearing? No problem. The seals/shields can be popped out with no trouble. Next time you'll know.
Bill.