In order to check if the electric motor is suffering from water damage, you need to first remove the motor and pump assembly.
Close the bleed valve of the log splitter and turn the machine upside down. There are three vertical bolts that hold the pump bracket to the underside of the end plate and a fourth horizontal bolt at the top of the rear motor cover. Remove these bolts and lift the assembly clear. There are 2 small O'Rings between the pump bracket and the end plate, make certain you do not lose these.
Next, remove the 6 bolts holding the pump bracket to the pump plate and remove the pump bracket. Check that there is no silicone sealant trapped in the pump gears. Try turning the fan again to check if the gears are turning okay.
If the gears are fine, then it's likely the motor has suffered water damage. Withdraw the shaft locating the upper gear and the lower gear. There is a small ball bearing located on the gear of the shaft, do not lose this.
Next remove the gear from the motor shaft. There is a cylindrical key in a solot in the shaft, remove this key. You can then remove the 3 long bolts that run from end to end of the motor and remove the motor end cover.
If there is water damage, you will see white deposits inside the aluminium casing and more than likely notice a strong pungent smell. If this is the case, the motor will need to be replaced.