As a general rule of thumb, if the motor shifts and/or has seals (grease retainers) on the drive and prop shafts, it uses gear oil. If not, a soft grade of grease, such as JD Corn Head, should be used. This grease thins out when worked and will get into all of the bushings and bearings which a thicker grease can’t. The gearcase still has to be drained of water and have the grease replenished regularly though.
Since grease is oil which has had thickeners added to it, the ‘grease’ lettering on the gearcase can be a bit confusing at times. The design of the gearcase dictates whether it uses oil or grease with oil being the preferred lubricant.
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