I tank tested my boat at dry dock to check shifting and to warm up the
block for changing oil and did not notice (but didn't think to look
closely) any additional water in the bilge.

After launching my new project boat we motored, to the dock where we
stayed stayed for about 24 hours before delivering her approximately 15
miles to my marina. During that period, the bilge did not seem to gain
any additional water.

After our delivery trip, I noted a significant amount of water in the
bilge. I manually switched on the bilge pump and noted it pumped for about
10 seconds until dry. I then completely emptied the bilge using a manual
pump and finally a sponge.

I chalked the water ingress up to the slightly rough ride as we had tons
of spray washing over the bow and into the cockpit.

Came back four days later and noted no additional water ingres. Took the
boat out on another 15 mile trip in very calm weather, and noted a bilge
full of water. Obviously the problem occurs only when the boat is
running.

The boat is a 28 foot Wellcraft with all new transom seals powered by a
Mercruiser 260HP (350 GM Block) mated to an Alpha 1 outdrive. The second
time I drained the bilge, I could feel a slightly oily residue in the
water, but not enough to show a sheen. For all I know that may have been
residual oil from a previous leak or spill. I checked my oil and noted
the level and consistancy had not changed.

Here are my questions:

Where are all the water drainage passages or petcock valves on this
block? Is it possible someone left a valve open during the winterization
process? How much water would an open valve dump into the bilge.

Could this be an exhaust manifold or riser problem? If so, can it be
occuring at only higher RPMs?

Could this be a hull problem even though there is no water ingress when
the boat is docked? Could my movement be forcing water through a crack
in the hull, but remain watertight at dock?

What are some other possible causes that would explain this problem?

When I head back up to the boat, I'm going to try running the boat and
noting any ingress at the dock. Running for several minutes above the
2000 RPMs, I'll also try in gear while docked at reduced engine RPMs

As always, any help in solving this scooby mystery is appreciated.

Bob Dimond