Hello, New to the forum but like it already. Went out last weekend and noticed later that day when i open the engine hatch that some dark brown/almost black thick substance was under the sea water pump area and looked like it dripped onto the engine belt as it was all over the wall. was no water in the engine compartment. No overheating alarm. Moter has 190hr on it but impeller was changed out at 138 when i bought it.

Make sure it's not coming from the dipstick tube or valve cover/bolts and dripping down.

Sea water/fuel pump assembly could also have a bearing seal out at front. They do have oil in them. Could simply be the drain on the pump housing too...