The 787 and 947 engines have a counterbalance oil reservoir that the Sea Doo manual says needs to be checked every 50 hours. The 787 though has what I consider a design flaw since there is no seal between the crank main bearing next to the cylinder and the crank counterbalance gear. Only a Labyrinth washer separates the counterbalance reservoir from the rear of the crankcase. In time, any oil added to the counterbalance area on a 787 will eventually dissipate so if possible, I would add oil whenever possible to the reservoir to prolong gear life. Also note that if you get water in the crankcase of a 787, it will also get into the counterbalance reservoir so you would need to remove the drain plug under the reservoir and get the water out. If not, your engine wonít be around for long!
As for the 947 (951), the manual doesnít tell you how to check the counterbalance oil or how high the oil should be, but when I get that info, Iíll add it!
Below you can see what plug or fitting needs to be removed to check the reservoir level.
The manual states the 787 & 787 RFI should have 30 mL (1 oz) SAE 30 motor oil in the reservoir.
The manual states the 947 & 947 DI should have 40 mL (1.35 oz) Jet Pump Synthetic Oil or standard gear oil in the reservoir.
(note that 1995-1996 787 donít have a check/fill plug. Oil is added when the engine is assembled and thatís all you get)
In my opinion, on the 947 (951) just adding oil especially to low/old oil seems like a bad fix. The oil not only should be checked, but should be changed maybe every 200 hours. If you have your engine out,you might consider adding a fitting to the lowest point of the reservoir so oil can be drained.
I may work on a kit to offer for this one soon if demand warrants it!