Mercury Oiler Gear

[99fxst99]

I spun the drive gear out of a 2.4 on my twin engine Seebold making a rough water run back down the James River. I was on the wheel but I had Captain Morgan on the sticks. That may have had something to do with it....��

[Capt.Insane-o]

different part numbers, different gears... one is one piece "twist on" with one screw and one is two piece with two screws.... either will work on any oiler crank.. almost ALL failures happen 'cause of several "minor" or one "major" overheat at some point in time.. then there is age, wear... jus like any other part in tha thing!

One is a "Tang" drive and the other fits around a machined surface of the crank.

[Fishinmymission]

Different gear designs have different factors such as angles they can interact, loads they can withstand, and how much the gear teeth flanks roll or slide.
Helical gears in your car transmissions and spiral bevels in your differentials have very little sliding between them and are mostly rolling and there fore have less wear and heat generation.

The worm gear used on oil injection system has some of the highest sliding contact but they needed a worm gear unless they added a belt or worked off the flywheel or something. Mercury was probably expecting high wear at this interface and opted for wear particles that would not harm the rest of the engine vs metalic chips. Also with lubrication in a two stroke crankcase being inferior to a four stroke with an oil pump, nylon is a little more self lubricating and forgiving than metals.

They realized the design was not as robust as it could be after 2 decades and they switched to electric oiling pumps on both the EFIs and DFIs.