Mercruiser 165 I6 venting oil above 3...

Author Message   antoine williams New member Username: tuandabrainz Post Number: 1 Registered: 05-2008 Posted on Monday, May 12, 2008 - 09:28 pm:    Guys, This is a weird problem that I really need help with. This engine is a 1979 that I have replaced all of the gaskets and seal on except the front oil seal and the timing chain cover gasket. When I run the engine, anywhere from idle to 3500 rpm, the machine runs as smooth as silk, with no issues. When I run at 4000 rpm, I get oil all over the top of the engine. At first, I thought it was being sucked out at the breather opening of the valve cover and being spit out where the hose connects to the flame arrester. I installed a PCV valve here, and got the same thing. I cannot watch to see exactly where the oil is coming from, because I am in the boat alone and can't leave the wheel to watch the engine, and I with muffs, it runs fine because I can't rev up that high without damaging the stern drive water pump impeller. As I said, all the other seals and gaskets are new, the compression reads about 140 on all six cylinders,and if it were a bad gasket or seal, it should leak at idle or at 3500 rpm. The next step is to take off the outdrive and run water directly to the engine so that I can test it at 4000 to see if it vents and where it is coming from, but before I do, has anyone seen a problem similar to this? Its really driving me crazy.   Rod Stewart Senior Member Username: rod_stewart Post Number: 1290 Registered: 08-2006 Posted on Monday, May 12, 2008 - 11:50 pm:    Sounds like you have excessive blowby that is pressuring up the crankcase and forcing oil out the breather instead of letting it run down the galleries back into the oilpan. It happens. Rod   Guy Gaspar Senior Member Username: guyjg Post Number: 2018 Registered: 08-2006 Posted on Tuesday, May 13, 2008 - 12:07 am:    Just to add to Rod's comment; pull the valve cover and check the oil return galleries for sludge which would not allow the excess oil to drain out of the valve cover and start spitting it out.   antoine williams New member Username: tuandabrainz Post Number: 2 Registered: 05-2008 Posted on Tuesday, May 13, 2008 - 10:55 am:    Other than cleaning these galleries, is there anything else I should look for? Does this amount of blowby mean I should change the rings even though the compression test was good?   Rod Stewart Senior Member Username: rod_stewart Post Number: 1299 Registered: 08-2006 Posted on Tuesday, May 13, 2008 - 12:00 pm:    Antoine; A good way to tell about ring blowby is a leakdown test. It is tricky but doable. How many hours on the engine? If more than a few hundred, blowby is a definite possibility. Have they ever been rebuilt? Removing the drive and running at high RPM with no load may not prove anything. High loading is when you get the worst blowby. Rod   antoine williams New member Username: tuandabrainz Post Number: 3 Registered: 05-2008 Posted on Tuesday, May 13, 2008 - 12:39 pm:    Rod, I bought this engine used from a marine liquidator, so I don't know if it has been rebuilt, or how many actual hours are on it. I had actually planned to rebuild it myself at the end of the season. Because of the compression test reading normal and the motor did not seem to have any mechanical noise while running I didn't think it was urgent to rebuild it right away. A little more info, is that this is a smaller engine than was originally in this boat which I bought from the same liquidator, so the load is higher on it for sure. Also, the drive is actually from another boat that I had that had a 140 engine in it, so the gear ratio is not correct, but I planned on offsetting this by specing a new prop to compensate. I know that every engine has some amount of blowby, but wouldn't excessive blowby be indicated by a bad compression test? This weekend I will check the oil galleries to make sure they are clear, and if they are I will set up to do a leak down check, but If I had a leak I thought it would show up on the compression test. Any more guidance you can give me is greatly appreciated.   Rod Stewart Senior Member Username: rod_stewart Post Number: 1303 Registered: 08-2006 Posted on Tuesday, May 13, 2008 - 12:55 pm:    Was the compression test done hot or cold? Results can vary. The only other way to be sure is to take a friend out with you, and while he drives look carefully at where the oil is coming from. I would hold the valve cover vent tube away from the arrestor while you do this, to be sure of what is going on. What kind of oil are you running? Rod   antoine williams Member Username: tuandabrainz Post Number: 4 Registered: 05-2008 Posted on Tuesday, May 13, 2008 - 02:45 pm:    Rod, The test was done cold. That would mean no expansion of the metal, and if it was going to leak it would leak the most then, correct? As for the oil, I think it was 40 weight. I don't remember. But, I do remember that it was some cheap stuff that I was going to change out later anyway, because when I had the engine apart changing all the gaskets and seals, I used a lot of cleaning lubricant to clean up the valve rockers and other parts. I cleaned it off as much as I could before I reassembled everything, but I knew some of it would still end up in the oil pan. I am going to drain it all anyway, put a new filter on and use a marine grade synthetic oil, whatever weight is recommended in the manual. Basically, this was only the second test run to see if there were any other bugs I needed to work out that might require removing the engine, and the third time the boat has even been in the water. I had some issues with the transom seal I had to correct the first time, so she is a work in progress.   MistaHays Advanced Member Username: mistahays Post Number: 688 Registered: 02-2006 Posted on Tuesday, May 13, 2008 - 03:37 pm:    Are they automotive valve covers? Are there crank case breathers on both valve covers? If not, add another on the other side. This is a common challenge with high revving race engines - worn out or otherwise. This can probably be solved by a different set of valve covers with larger diameter breathers - thus lowering the velocity of exiting gasses - and taking less oil along with it. Of course, if you have a compression issue, that should be addressed as well. My thoughts. Hays   antoine williams Member Username: tuandabrainz Post Number: 5 Registered: 05-2008 Posted on Tuesday, May 13, 2008 - 04:59 pm:    Mistahays, it is an inline engine, so there is only one valve cover, and it is a Mercruiser valve cover.   Rod Stewart Senior Member Username: rod_stewart Post Number: 1307 Registered: 08-2006 Posted on Tuesday, May 13, 2008 - 05:22 pm:    antoine; Any chance there is too much oil in it? Did you put the specified amount of oil in? Just wondering; its possible it has the wrong dipstick in it, and if the oil level is too high, it may be whipping it into a spray that is then going out the breather. Just a thought, though pehaps not too coherent! Rod   MistaHays Advanced Member Username: mistahays Post Number: 693 Registered: 02-2006 Posted on Tuesday, May 13, 2008 - 10:57 pm:    More coherent than my last post! Rods right. too much oil? Oil drains through the head from the rocker gallery stopped up? In the short term you can always duct it into a can with an exit pipe from the can back to the intake. That way you can measure the amount of oil loss and it won't be a safety issue. You certainly don't want any pressure buildup, as thats the way you end up with rear main and other seal leaks.   Bert Goodrich Member Username: bertg Post Number: 89 Registered: 10-2006 Posted on Tuesday, May 13, 2008 - 11:27 pm:    antoine williams Is the baffle inside the rocker cover over(under) the breather in place? There is also a breather chimney shown on the parts explosion. Bert   Troy Advanced Member Username: troym Post Number: 508 Registered: 09-2004 Posted on Wednesday, May 14, 2008 - 05:55 am:    Are you sure you put the PCV valve going the right direction? It should allow vapor to flow from the valve cover to the suction of the intake, and should close in the event of a backfire through the intake (prevents a crankcase explosion). Also, with the PCV valve installed, there is going to be more head loss in that line. If you still have that cheezy corrugated crap, replace it with smooth tubing. And, if you still have it hanging in the air stream in front of the flame arrestor, you're probably not going to have enough pull to suck the oil vapor and blow-by gasses out to properly ventilate the crankcase. With the PCV valve installed you're going to have to direct the crankcase vent line to the inside of the flame arrestor. I had a similar issue with my 5.7L after installing a new short block. Pumped oil out the front main seal like crazy until I replaced the crankcase vent tubes, installed pcv valves and directed the lines into the top of flame arrestor through a tee fitting. Keep one thing in mind: what I'm proposing is drilling a hole in the top of the flame arrestor to attach the crankcase vent line. The flame arrestor is there to prevent a backfire through the intake from igniting any fuel vapor that may be lingering inside your engine compartment which would burn your boat to the water line. Make damn good and sure any lines you attach are tighly secured (hose clamps, threaded mechanical fittings, etc.) so that in the event of that backfire the pressure is relieved through the flame arrestor, not by blowing off one of the modifications you made, bypassing the flame arrestor. Plus it's always a good idea to keep your engine compartement vent fan running anytime you're running the eninge and going less than a decent cruising speed. The boat should have a vent system that takes care of keeping air moving through there when it's at cruising speed.   Rod Stewart Senior Member Username: rod_stewart Post Number: 1311 Registered: 08-2006 Posted on Wednesday, May 14, 2008 - 12:36 pm:    Troy; I like your approach. Those are all excellent points that all of us should adhere to IMHO. Rod   Guy Gaspar Senior Member Username: guyjg Post Number: 2027 Registered: 08-2006 Posted on Wednesday, May 14, 2008 - 12:37 pm:    Troy et al: I am only slightly familiar w/this engine. Is there a plug in the intake manifold that could be replaced w/a nipple for the PCV hose? If not, could a hole be D&T for one?   Troy Advanced Member Username: troym Post Number: 510 Registered: 09-2004 Posted on Wednesday, May 14, 2008 - 12:58 pm:    Guy, Probably could, but I'd be careful with how much air flow you're going to allow to bypass the throttle.   Guy Gaspar Senior Member Username: guyjg Post Number: 2030 Registered: 08-2006 Posted on Wednesday, May 14, 2008 - 04:11 pm:    Troy you're right; the increased vacuum at the hose may also suck more than blow-by gases such as oil!   antoine williams Member Username: tuandabrainz Post Number: 6 Registered: 05-2008 Posted on Wednesday, May 14, 2008 - 05:31 pm:    Rod and co.. Its possible there is too much oil. This is something I plan to check when I test it out again this weekend. What troy is suggesting is a modification that I shouldn't have to make. This model I originally did not even have a real PCV valve, just a metal nipple inserted into the PCV Grommet, and this is the normal setup I found out recently.I know that vapor is being sucked out of the valve cover properly, because if you hold a flashlight next to the breather tube at the flame arrester you can see it being sucked into the flame arrester. If it is not too much oil in the resevoir causing the problem, and the oil return galleries are clear, I would think that it has to be blowby of the rings, even though the compression test is good. But is it possible that 3500 is maximum for this particular engine with the configuration that I have, and that by exceeding that I'm over revving the engine? Does overevving cause oil venting? It seems to me that if there was a problem of too much oil, or blowby, or some other mechanical issue, I should be getting oil blowout at any rpm, even idle. Now, as for blowby, I will do the leak down check this weekend. Assuming it is the rings, do any of you know of a master rebuild kit that does not cost a fortune? I actually can't even find a marine rebuild kit for this engine, only automotive, and I don't want to use that. I also don't want to drill holes in the top of the arrester, because this engine was originally designed to run with the current setup, and if it doesn't that means there is a problem that I need to fix. I shouldn't have to rengineer the thing for it to work. Thanks for the suggestion anyway though.   Guy Gaspar Senior Member Username: guyjg Post Number: 2032 Registered: 08-2006 Posted on Wednesday, May 14, 2008 - 08:42 pm:    Antoine: Click on ENGINE PARTS above and put this number 27-801841 in the search for OEM parts.   Troy Advanced Member Username: troym Post Number: 515 Registered: 09-2004 Posted on Thursday, May 15, 2008 - 08:09 am:    4000 rpm shouldn't be an issue. WOT should be a few hundred above that. Over-revving is not the issue here. As far as pumping out oil at any rpm, not so... the oil pump is a gear type pump driven by the engine, the faster the engine spins, the more oil it will pump. Plus, many engines get oil to the wrist pins and cylinder walls by splash-feed. When the bottom of the rod caps hit the oil in the oil pan, it squirts oil through the passages up through the rod. Once again, the faster the crank is spinning, the more churn there will be. So it makes sense that it's only spewing oil at higher rpms. Just had another thought, and I'm going to have to ask for some help on this one. I know on bigger engines (really big engines), pressure fed oil systems that have pumps driven by the engine have relief valves to limit the oil pressure. Is this the same here... could the relief valve on the oil pump (or elsewhere in the system) be stuck shut?   Bert Goodrich Member Username: bertg Post Number: 90 Registered: 10-2006 Posted on Thursday, May 15, 2008 - 11:43 am:    Troy I dunno. I haven't heard of a "Splash Oiling System" since the late 40's on any North American Vehicle. The school of thought on the splash system today is that any crank/rod movement through the oil reserve causes the oil to foam, thus limiting its effectiveness, when it is pumped through the engine. Any engine I've rebuilt in recent times has an oil pump with positive pressure, both automotive and aircraft. They all have the connecting rods drilled to pass oil from the bearings up to the wrist pin end to direct oil into that area. JMHO Bert   Troy Advanced Member Username: troym Post Number: 517 Registered: 09-2004 Posted on Thursday, May 15, 2008 - 12:11 pm:    You're right Bert. I said "many", probably should have not bothered mentioning it. Just trying to emphasize methods employed to deliver oil to various parts of engines are dependant on or affected by the engine speed. I did do a little reading on oil pumps. Seems there is an integral relief valve... could be worth looking at if the leak-down and compression tests don't show anything conclusive.   Bert Goodrich Member Username: bertg Post Number: 91 Registered: 10-2006 Posted on Thursday, May 15, 2008 - 12:23 pm:    Troy Point taken. I don't think he is having a oil pressure problem. It sounds like a pressure problem within the engine. Thus my pointing to the baffles and chimney in the valve cover. If they are missing or mis aligned oil will be coming out the breather area on droves. It would take a lot of blow by to expel oil out the top if the baffles were in place. With 140 compression across the engine, I doubt if too many gases are getting by the Compression rings. As of yet I haven't seen any mention that he put a driver at the controls and went back and visually inspected where the oil is coming from. We all may be barking up the wrong tree here. May be a simple oil leak, blown head gasket?? Bert   antoine williams Member Username: tuandabrainz Post Number: 7 Registered: 05-2008 Posted on Thursday, May 15, 2008 - 04:13 pm:    Bert, I am currently out of town on business. As I've said in a previous post, I plan on checking out all of the suggestions I have been given this weekend, and reporting back with what I find, yours on the baffles, and another visual check on the water running WOT with another driver (already asked my brother to go with me). That will be done first, because I am reluctant to pull the engine again if I do not have to. I appreciate everyone's input, and I just wish I could get back sooner to look at it all now. As for a head gasket, I don't think so, because I don't appear to be burning oil, there is no smoke at the exhaust, and no oil residue at all in the exhaust water. Also, there is no sound of water in the cylinders. Oil leak, I can possibly see, but as I said before, if it simply a bad gasket or something, I should be seeing oil flowing as soon as the engine warms up, (I had a leak on a four cylinder engine from the rear oil seal that would not show up till about 5 minutes or so after the engine was started, then would flow freely). I actually hope it is something simple, it would save me time and money   antoine williams Member Username: tuandabrainz Post Number: 8 Registered: 05-2008 Posted on Monday, May 19, 2008 - 12:04 pm:    Ok fellas, I ran the boat wide open this weekend with someone else at the wheel, and the oil was not coming out of the breather like I thought. It is coming out of the top corner of one of the push rod covers and because it is under pressure it is showering the whole top of the engine with oil. I checked the oil return galleries before the trip, they are clear, I checked the baffle in the valve cover, and it is in place. I checked the oil level, which was actually empty from venting all the oil last time. I put in 4 quarts of SAE 40 heavy duty oil (the book calls for 5, but I could only find 4). I think that either the seal is bad (even though it is a new seal)the cover is bent enough to not seal properly, or I am in fact getting blowby that is causing me a pressure problem. The only thing is, the pressure reading on my oil gauge never went above 40. If I am getting blowby, shouldn't this reading be very high as an indicator that there is a problem? I am getting fittings to do a leak down check next.   Troy Advanced Member Username: troym Post Number: 529 Registered: 09-2004 Posted on Monday, May 19, 2008 - 12:15 pm:    Oil pressure is right where it needs to be, and wouldn't indicate excessive blowby. Oil pressure is based on the speed of the engine until the relief opens, and the flow characteristics of the lubrication system and bearing clearances. Crankcase pressure would have a negligable effect on oil pressure. If the things that would cause crankcase pressure to go up were so severe that it would affect oil pressure, it'd be pretty unlikely the engine would run anyway. The leak down check will tell all WRT excessive blow-by, but I'd bet you're not going to get anything conclusive out of it. Seems there would be other symptoms... lack of power, knocking, etc.

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