Bravo 3 Propshaft Seal

[390Express]

Got my boat out and replaced the (destroyed) propshaft seal. Once out of the water, it had gear lube pouring down the skeg. Replaced the prop shaft seal, and all is good... but, what causes the prop shaft seal failure? Is this just something that happens over time? Is it caused by a worn lower? too heavy in reverse? too much prop vibration?

Just trying to get an idea as to whether I have a bigger issue going on, or if I need to correct something going forward.

 

[kghost]

1. Merc has a spec on prop run out. I believe at the taper is to be .003" or less. Typically you would feel some vibration but maybe not.

2. Crap wraps around prol shaft, especially fishing line and that will tale out prop shaft seals.

3. Very Dirty/sandy water, the crud will find its way to seal.

Operation alone will not cause issues.
Age also can cause seal failure BUT you dont give a year of drive/boat. Seals only last so long.

 

[390Express]

1. Merc has a spec on prop run out. I believe at the taper is to be .003" or less. Typically you would feel some vibration but maybe not.

2. Crap wraps around prol shaft, especially fishing line and that will tale out prop shaft seals.

3. Very Dirty/sandy water, the crud will find its way to seal.

Operation alone will not cause issues.
Age also can cause seal failure BUT you dont give a year of drive/boat. Seals only last so long.

Thanks for the reply.

I do boat in shallow water with a sandy bottom, and sometimes kick up sand. Generally at idle speed, looking for a spot to anchor. When I do kick up sand, it's brief, and very temporary.

The seal may have been original and lasted the first 600 hours, and 27 years... I just want to make sure it's not something that I'm doing, or overlooking. Replaced it last week, and so far, so good.