Dear Motorhead,

I am having the problem of water in the oil of my model 750 - 4 cylinder Gray Marine engine. I have recently replaced the cast aluminum oil pan which was cracked, with a cast iron replacement. I am not using the oil cooler (which was also cracked) and have connected the outlet on the side of the engine block (from the oil pump) directly to the oil distribution line. There can be no water from this source. I have removed the cylinder head and there are no cracks or leakage and it will hold air pressure (I did not use a high pressure.) The cylinder walls, as far as I can see, all look OK.

Most of the valves and seats look OK. Other than some rust pitting on the ones on the front of the engine as it is mounted in the boat, compression from the front to back: 45, 60, 72, 75. Oil pressure is good (30 lbs.) I have run this boat about 30 minutes mostly wide open throttle and did notice some white smoke out of the exhaust. The oil is all white and probably 1/2 to 1 quart above normal fill mark on dip stick. This engine was not run for the past 10 years or so until after my recent work on it in August, ‘98. I cannot figure how the water is getting into the oil. Any ideas? I have not yet removed the engine from the boat. I have several other boats and have never had this problem. I have not magnafluxed anything on this engine yet.

The Gray Marine maintenance manual says, “the commonest cause of persistent trouble with sticking valves in marine services is water in the valve chamber either from condensation caused by running too cold or kick-back of overflow water caused by an oscillation in the exhaust pipe.” In my installation overboard water dump is very low at the rear of the engine at the bottom of the exhaust elbow. Also, the engine is at a steep angle which would require water entering engine from the exhaust pipe to run uphill considerably. Ever hear of this?
I enjoy your column very much.
Sincerely,
Bob McBride

Dr. Motorhead Responds...

Bobby, Bobby, Bobby. I sure hope your 19 foot barrel back is running better than this Gray Marine. By the way, I haven’t seen you in a while, how is Balsam Lake? I’m sorry to be the bearer of bad tidings, but you have major problems everywhere. I’ll pick at them one at a time for you, but while you are wintering in California, save up some dough; it’s time for a major overhaul.

First off, disconnecting your oil cooler is OK for a test but they put them on there for a reason. Keep in mind, that not all the oil goes through this cooler. This is usually only the oil that feeds the top end of your engine, therefore, you did a good thing by bypassing the cooler and not capping off the line. You could have had additional problems. 

Secondly, the reason your compression is weak in the front two cylinders is because of the rust and pitting on the valves and seats. Your compression should be consistent and around 85 pounds on that engine when fresh. So my friend, you need a valve job. Those front two cylinders sat for 10 years with fully or partially-opened valves, allowing moisture to enter and rust things up a bit. As for white smoke, most commonly, this is oil burning in the combustion chamber. Your rings aren’t working well and they are letting some oil sneak by -- I would guess in those front two cylinders again. 

I’m not sure why you referenced the amount of water coming out of your exhaust. The reason for this low volume is, all the water is dumping into your oil pan (just kidding.) Remember, this is a small engine with a small water pump. I would think without looking at it, this is totally normal. Don’t worry about water kicking back into your exhaust manifold -- very, very unlikely. Are you sure the manual used the word “commonest” in that sentence? They must have fired the proof reader.

Sorry to hear that your oil now resembles Ovaltine. This is the worst news for you today. The key word you used twice in your letter was, “cracked.” There are only two ways these pieces could have cracked. Either someone dropped your engine onto the garage floor or it was stored over the winter without draining all the water out. The engine block and head have water channels running all through them to keep things cool during operation. If you had a cracked head, cylinder wall or a bad head gasket, this could allow water into the oil. But when this happens so close to the combustion chamber, the engine usually runs pretty rough. As you know, water doesn’t burn as well as gasoline. If you don’t see any cracks in your cylinder walls, that is good. Now when you rebuild, you won’t have to install any sleeves in your block. There is a good chance, in fact I am almost certain, that your block has cracked somewhere lower. Probably just above your cam. Before you send everything off to get magnafluxed, pull your engine and drop the pan. With a garden hose pumping water through your engine, take a look for any water dripping out of the block up by your cam or by the bottom of your cylinders walls. I think you will find your problem. If by chance you don’t, then you will need to bring it in to have it magnafluxed. For those of your who don’t know what this is. your engine is magnetized and iron filings or dust is sprinkled on it. The iron filings tend to congregate and bridge over cracks, even the tiniest, allowing you to see those cracks when normally, you can’t. Cracks can be welded, so don’t despair 
So, my friend, like I said, it’s time for that major.