I just got a "projectboat" a 1988 ebbtide 170 with a OMC Cobra 3.0 stern drive. When I first saw the boat the guys had a hard time getting it started, it turned out to be the points and when they were replaced the engine started right up. The guys working to start the engine were very careful to have water running thru the muffs each time the engine was cranked over. I had checked the engine oil while they were working on the engine and it was slightly dark but had no signs of water or other contamination.
It was over a week later that I picked up the boat and had a test run in the lake just before bringing it home. She started right up, seemed to run fine, shift fine, although at WOT it was running at 5,000rpm. I figured a different prop or more careful use of the throttle. Again I checked the oil and no sign of any water.
After I got the boat home my wife and I cleaned it up and I drained the oil in preperatio to change it. It was milky with water!! I rigged up a block pressure test apperatus and the block held 20psi for over 24hours. I removed the manifold, cleaned it in muriatic acid and tested it by filing with acetone as I had seen on a post online. No sign of leakage in the manifold.
Thinking the water in the oil may have happened when the guy at the boat yard pressure washed the interior and engine while I was paying for the boat, put in 10w30 oil just to kind of flush out any more moisture and try out the boat to see if any more water got into the oil. (drained and refilled the out drive also, the drained lube was clean, free from water or metal.) Started and ran the engine on the muffs and other than a bit of a rough idle it ran good. checked oil-no sign of water. Took the boat to the lake for a short run (about 1hr.) ran great, no problems, no water in oil.
A couple of days later we took it out for about 3hrs. and again ran great no problems and no sign of water in the oil.
I decided to adjust the valves and change to 30wt. oil. when I removed the valve cover the oil was like new with again, no sign of water. I adjusted the valves and changed the oil and started the engine but noticed more noise that I thought was good. I again removed the valve cover to try to adjust the valves again, this time with the engine running, and the milky oil/water mixture was back!!
At this point I decided to check the compression and it was right at 145-150 for all cylinders. I did notice a white mist coming from the #4 cylinder while the engine was being turned over. I caught the mist on a paper towel and it was clear and had no odor. The other cylinders had no such mist.
Some other possibly important observations-I was not very careful to turn off the water to the muffs between runs, could excessive water have found it's way in to the engine thru the exhaust? When I took the exhaust bellows off there was no "flapper" in the big pipe. There is a small bar across the pipe which I believe the flapper could hang from. With 150psi compression it seems unlikely that the water could go thru the exhaust valve and past the rings to the pan.... I have not noticed any hesitation to turn over from hydro lock when trying to start the engine and it seems to go many starts/runs with out the water getting the oil.
My next test will be to remove the manifold again and try to rig up a pressure test fixture so I can test the manifold under water. After that probably a complete motor rebuild. With the 30wt oil it had about 20psi oil pressure at idle and 40+ at 3500rpm. Not knowing how much water has been in the oil or how long it ran that way, is there any chance the bearings etc. are still ok to run? I'm still concerned about the noise I hear but I cannot locate it with my mechanic's stethoscope. Engine sounds smooth and even with the 'scope.
Sorry for such a long post but I wanted to detail my problem and observations.
Thanks for any comments,
Ned
It was over a week later that I picked up the boat and had a test run in the lake just before bringing it home. She started right up, seemed to run fine, shift fine, although at WOT it was running at 5,000rpm. I figured a different prop or more careful use of the throttle. Again I checked the oil and no sign of any water.
After I got the boat home my wife and I cleaned it up and I drained the oil in preperatio to change it. It was milky with water!! I rigged up a block pressure test apperatus and the block held 20psi for over 24hours. I removed the manifold, cleaned it in muriatic acid and tested it by filing with acetone as I had seen on a post online. No sign of leakage in the manifold.
Thinking the water in the oil may have happened when the guy at the boat yard pressure washed the interior and engine while I was paying for the boat, put in 10w30 oil just to kind of flush out any more moisture and try out the boat to see if any more water got into the oil. (drained and refilled the out drive also, the drained lube was clean, free from water or metal.) Started and ran the engine on the muffs and other than a bit of a rough idle it ran good. checked oil-no sign of water. Took the boat to the lake for a short run (about 1hr.) ran great, no problems, no water in oil.
A couple of days later we took it out for about 3hrs. and again ran great no problems and no sign of water in the oil.
I decided to adjust the valves and change to 30wt. oil. when I removed the valve cover the oil was like new with again, no sign of water. I adjusted the valves and changed the oil and started the engine but noticed more noise that I thought was good. I again removed the valve cover to try to adjust the valves again, this time with the engine running, and the milky oil/water mixture was back!!
At this point I decided to check the compression and it was right at 145-150 for all cylinders. I did notice a white mist coming from the #4 cylinder while the engine was being turned over. I caught the mist on a paper towel and it was clear and had no odor. The other cylinders had no such mist.
Some other possibly important observations-I was not very careful to turn off the water to the muffs between runs, could excessive water have found it's way in to the engine thru the exhaust? When I took the exhaust bellows off there was no "flapper" in the big pipe. There is a small bar across the pipe which I believe the flapper could hang from. With 150psi compression it seems unlikely that the water could go thru the exhaust valve and past the rings to the pan.... I have not noticed any hesitation to turn over from hydro lock when trying to start the engine and it seems to go many starts/runs with out the water getting the oil.
My next test will be to remove the manifold again and try to rig up a pressure test fixture so I can test the manifold under water. After that probably a complete motor rebuild. With the 30wt oil it had about 20psi oil pressure at idle and 40+ at 3500rpm. Not knowing how much water has been in the oil or how long it ran that way, is there any chance the bearings etc. are still ok to run? I'm still concerned about the noise I hear but I cannot locate it with my mechanic's stethoscope. Engine sounds smooth and even with the 'scope.
Sorry for such a long post but I wanted to detail my problem and observations.
Thanks for any comments,
Ned
