Just Baffling - Leak in Engine Compartment Basin

[jamhass]

What have been the weather/sailing conditions? Do you take water on deck when this happens? We had a similar "only underway" leak that (eventually) proved to be a leaky deck drain hose such that it drained to the area under the engine.. Also check other deck penetrations, such as water/fuel fill points, etc. Their bedding may have failed.

[Don C L]

Originally Posted by kapnd

Rudder shaft seal above the waterline?
Little Wing suggested checking it out underway.
If the seal is above the waterline, it possibly never got properly adjusted, as the only time it’s wet is when underway, and water is forced up it.

That was what occurred to me too; just a long shot here because I don't know how the Beneteaus are constructed. Could water go up the rudder shaft and leak from the seal there? Does this happen under sail as well?

[C420sailor]

Apparently the void inside the skeg is filled with a large amount of resin after the fiberglass stern tube is installed. It is very common for the resin to shrink while curing and crack, and any cracks or leaks in the stern tube allow water to move out of the tube, up through the resin cracks, under the diesel tank, and down into the engine bilge/prop shaft basin. Worth looking at.

[Snowgoose71]

Here are a couple of pics..

[cpasquin]

I had a Beneteau 50 1998. I spent a lot of money to change all of the above, and after 2 years found it to be the the U shape siphon breaker on the engine that was sometimes leaking from its exit tube while underway.

[Cadence]

I'll bet it is your shaft seal. Is it a regular old packing gland or something else. Have you checked your motor mounts for allowing vibration?

[stormalong]

Originally Posted by Cadence

I'll bet it is your shaft seal. Is it a regular old packing gland or something else. Have you checked your motor mounts for allowing vibration?

I agree with Cadence. You say this only happens when the engine is running.

I don't recognize that shaft seal. If it is conventional packing some drip is needed for cooling/lubrication. If it is some kind of dripless seal it needs adjusting.

Just because it is new does not mean that it is OK.

[Snowgoose71]

It is a Volvo Penta dripless shaft seal....the shaft and the shaft seal were both replaced at same time to make sure there is a good connection of the rubber lip to the ss shaft (no pits, etc). The dripless has to be lubricated once a year with blue grease under the lip...

[roverhi]

Conventional prop shaft log are supposed to leak a small drip when the engine is powering the boat. The water is needed to lubricate/cool the packing in the shaft seal. Not the case with dripless shaft logs.

[Nicholson58]

I had a small leak in that same location. Turned out to be a damaged shaft log. We didn’t find it until it got worse. Hauled ground out and rebuilt damaged old fiberglass. End of problem.

We had another leaker in the cabin. Turned out to be a pin hole that allowed water to travel several feet along a layup seam. Really tough to figure out.

Try using a very bright light to locate the wet spot. Dry everything extremely well. Examine under way if possible and run your hand over the dry surfaces until you find it.