My water pump in my springer is actually for a water jet to squirt the kids with!
I must bloody finish that build!
Usually I fill my prop shafts with marine grease. That resolves most of the issue.
When prop shafts are flat/ square/ level to the motor your more likely to get water ingress up the shaft compared to motor shafts at an angle which actually tend to have the exit above the water line.
There is no 100% cure when the shaft is flat In a springer, or any other model running the shafts below the waterline and straight. All you can do is pack out that shaft best you can.
Some suggestions tho, around the shaft exit se if you can catch the water drips with either a water compartment( could fit an auto bailer) or just stick a small cloth under the shaft to catch the drips.
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