Propeller shaft leakage

[martini21]

We just picked up a 2004 Martini Launch 21' Yanmar 3GM30F with 30 hours on the original engine. The boat seems in near mint condition and everything works perfectly but this is pretty new to me, never having had an inboard propeller shaft. Is it normal for water to drip off of the propeller shaft into the sump under the engine?. I suppose that is what bilge pumps are for, but if it is normal, and if so what is acceptable? The good news is that we will have a boat lift up and running in a few days, but for now it is in the water.

 

[Wee Venture]

I don’t know about that boat specifically but traditionally inboards have a prop shaft that passes through a “stuffing box” with packing material around the shaft that is compressed with a gland nut. They are designed to drip a little bit to lubricate the shaft. Over time they may start to drip excessively and the gland nut needs to be tightened. Eventually the packing material may need to be replaced if it is leaking excessively and can’t be fixed by tighteythe nut. On my Ranger Tug (R-31) the gland nut is specified to be tightened to the point where there is one drip about every 10 to 20 seconds. The manufacturer of your boat should have specs on that but it will probably be similar. It is good to check the drip rate while the shaft is rotating.

 

[knotflying]

The above post is dead on. You should get no drip when not running. If you do determine that you need to tighten the nut use very small increments. I am talking about maybe a 1/16 to 1/8 of a turn at a time.

 

[hames57]

My 21 Classic drip rate is adjusted to one drop every few minutes engine off and one drip every every 5 seconds or so. at cruise. The engine off drip rate is really more of a weep than a drip.