Just did a compression test on 2003 Black Scorpion motor. Was really hoping to buy this vdrive inboard with 190 hours on it, but had to walk away for now. Owner changed all the plugs last week. I looked at it after he got it out of storage a few weeks ago, and at that time the oil was quite black, but good consistency and smell, as far as I could tell. He said it was a year old. He changed the oil and plugs, and we went for a test drive today. Boat performed very well for 15 minutes on the water, perfect temps and oil pressure on the gauges. Maybe just a tiny bit rough at times, but chalked that up to old gas.
Did the compression test on the dock, could not access the injector harness plugs and he did not know if it had a fuse box, so we decided to check one bank at a time without unplugging the MPI system (hope that was not a mistake?). We did ground the coil wire to the motor mount. The first 4 plugs on the starboard side looked great, new plugs, 160 to 180 psi. Putt the wires back on, started the boat, let it run for a minute, and moved to the other side. Pulled first plug and it was covered with black soot, not oily or smelly as I recall. I pulled the other 3 on that side - two inner plugs looked great, two outers were both black and sooty. Checked the compression on the two outers first, one was 150-155 and the other was 180. Decided then and there, I would need a marine mechanics perspective/inspection. At this point, the engine alarm started going off and we heard a squeal when cranking, so did not get to test the inner two on that side. I felt really bad though. But wonder if the alarm was related to low oil pressure, and the squeal did not make sense at all. Any advice from experienced mechanics appreciated.
Did the compression test on the dock, could not access the injector harness plugs and he did not know if it had a fuse box, so we decided to check one bank at a time without unplugging the MPI system (hope that was not a mistake?). We did ground the coil wire to the motor mount. The first 4 plugs on the starboard side looked great, new plugs, 160 to 180 psi. Putt the wires back on, started the boat, let it run for a minute, and moved to the other side. Pulled first plug and it was covered with black soot, not oily or smelly as I recall. I pulled the other 3 on that side - two inner plugs looked great, two outers were both black and sooty. Checked the compression on the two outers first, one was 150-155 and the other was 180. Decided then and there, I would need a marine mechanics perspective/inspection. At this point, the engine alarm started going off and we heard a squeal when cranking, so did not get to test the inner two on that side. I felt really bad though. But wonder if the alarm was related to low oil pressure, and the squeal did not make sense at all. Any advice from experienced mechanics appreciated.
