For water to get into your gearbox, it must have come past either the propeller shaft seals, the drive shaft seals or the gear selector seal. In rare cases the casing can be cracked from an impact allowing water in.
On this Yamaha outboard, fishing line wrapped around the propeller had cut the propeller shaft seals. In this video I take out the bearing carrier, replace the seals, then pressure test the gearbox to make sure the fix has worked before putting new oil in.
To find out which oil seal is leaking, it's best to pressure test the gearbox. This video shows how.
Replacing the propshaft seals the hack way
Open ›If the bearing carrier is completely seized into the lower unit you may have no choice but to hack the old oil seals out. This video talks about doing that.
Replacing the driveshaft seals on a Honda BF30
Open ›Caramel-coloured gearbox oil on a Honda BF30 points to water getting in past the seals. I free the corroded gear selector seal carrier, then replace its seal and the two back-to-back driveshaft seals.
Replacing the propshaft seals on an Evinrude 150
Open ›Changing the Evinrude 150 propshaft oil seal means pulling the bearing carrier from the gearcase. I show making puller arms from threaded rod, driving the new seal in square, and which O-ring keeps water out.
Replacing the driveshaft seals on an Evinrude 150
Open ›This topic covers replacing the seals around the driveshaft on an Evinrude 150. These seals are responsible for keeping the gearbox oil in and water out.
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