Seadoo (BRP) uses SAE 30 oil in the crankshaft counterbalance chamber (not injection oil), 30mL for the 787/800 engine.
You should have easy access to the counterbalance fill plug on the exterior of the cranckcase while the top end is off. I would at least check the condition of the oil that is in there while you have the motor(s) torn apart. Remove the fill plug and extract some of the oil to check it out. Having '98 motors, you should also have a drain plug at the bottom of the chamber to drain the old oil out if you need to.