Oil Leak!

[Chapmar]

Hi,I own a 28 ft Bermuda Bucanner with a bmc 1.5,have recently noticed oil in the raw water coolant coming out of the exhaust into river,although it is probably a small amount I’d like to stop this if possible,I have been told it could be valve seals and another person said possibly a blocked air pipe? I would appreciate opinions,engine is 1981 but regularly serviced.thanks.

[dnks34]

I cant think how engine oil could get into a raw water circuit, could it be from the Gearbox Oil Cooler?

[JanetAnne]

1 hour ago, dnks34 said:

I cant think how engine oil could get into a raw water circuit, could it be from the Gearbox Oil Cooler?

I'm with you on this one though we are automatically assuming a separate sealed cooling system?

I would also assume that any oil would look like mayonnaise by the time it reached the hull outlet.

I wonder if it's unburnt diesel that's being seen on the water surface? 

[Vaughan]

BMC 1.5s take a little while to warm up and you will often see a rainbow of oil on the surface near the exhaust, from unburnt diesel, until they get up to temperature.

They will often make white smoke when they are cold.

You could try retarding the injector pump slightly, but this may make it difficult to start, if you go too far!

[Vaughan]

I have just had a thought, that if you have only recently noticed this, it may be due to the cold weather in winter making more of a problem when warming up the engine.

By the way, welcome to the forum!

[Cheesey69]

oil would get into the raw water circuit via exhaust valve seals.

Into cylinder, out unburnt to mix with water injector at elbow and then over board.

The seals around the valve stems harden over time and this is more noticeable on first start as the oil has time to seep down the stems and will lessen as day goes on or valve stems/guides have worn.

Also, is the oil right grade? Too thin can leak past.

It will never get better and if this was a car it would emit a puff of smoke on start up.

Its not fatal just keep your on oil level as the fix, especially on a marine engine is a head off operation.

[annv]

Hi Do you have to top up the engine oil? if not it is as Vaughan said nothing to worry about, if you do use oil so what unless its pints every time you go out ,is there oil in coolant header tank? if so try tighten the head bolts down to correct torque.head gasket my be weeping at oil channel in gasket. John

[Vaughan]

1 hour ago, Cheesey69 said:

oil would get into the raw water circuit via exhaust valve seals.

 I remember on the early Nanni 4190 engines we had a problem of the bearing leaking oil under pressure, on the rocker shaft above the No 2 cylinder. This caused a fine jet of oil to shoot straight down the crankcase breather into the air filter and out of the exhaust in clouds of blue smoke.

It took quite a while to work out what was causing that!

[webntweb]

11 hours ago, dnks34 said:

I cant think how engine oil could get into a raw water circuit, could it be from the Gearbox Oil Cooler?

 

10 hours ago, JanetAnne said:

I'm with you on this one though we are automatically assuming a separate sealed cooling system?

I would also assume that any oil would look like mayonnaise by the time it reached the hull outlet.

We had a gearbox heat exchanger fail on Swan Raider 2 (Alpha 32 F/D) and it did indeed look like mayonnaise.

Had to chase ducks off as they were eating it.

[keifsmate]

I have an Elysian that suffered this problem. Although it is powered by a 4-108 Perky, the oil cooler in the raw water circuit had developed a leak and yes rainbows at the stern! A new cooler from ASAP soon sorted the problem.

[annv]

Perhaps i should add have got a gearbox oil cooler does the gear box oil look milky or do you have to top it up? when you remove the oil cap on the rocker cover is it covered with a creamy white scum? if so head gasket likely, tighten head nuts, also check rocker cover breather pipe to air filter by blowing down it from air filter if blocked remove cover and wash out with paraffin if cork gasket is iffy replace, then apply gasket sealer ONLY on cover side smear grease on engine side before replacing this will make it come off cleanly when removing for servicing. John

[Chapmar]

Hi,thanks everyone for your input,engine has hardly any smoke on start up or running,it does’nt use a excessive amount of oil,it was changed from Morris Classic 10w40w to Morris Servol 15w 40w in the summer,the oil that appears from the exhaust / water coolant is a rainbow type thin film which probably looks worse than it is,but would like to cure if poss,thanks for your help.

[Smoggy]

You can change valve stem seals without removing the head as long as you do them with each piston at tdc (do two then turn engine by 180 degs), just need a spring compressor that can hook on rocker studs, I did make one but gave it away after using on my old BMC 2.52's.

[annv]

Hi Rainbow streaks are more likely to be diesel give it a good run then check have you checked air cleaner? does engine run evenly?. John

[Cheesey69]

Just to be clear. 
Raw cooling water gets sucked up from the river, enters the heat exchanger, cools the sealed engine cooling water anti freeze mix and then gets injected into the exhaust flow at the elbow to cool your exhaust gas so it don’t melt the rubber pipe. 
Unburnt oil especially at start up because it hasn’t had time to burn will mix rather than smoke after that an engine burning lots of oil will have a particular smell

[Cheesey69]

Why I’m saying this mixing of anything into the engine is very serious as the oil level and pressure would rise making the engine smoke and leak from the breather mainly and you would notice this on your daily checks as the oil would rise up the dip stick. 
A leaking injector could to the same but again you would notice the oil level rising. 
On balance and from distance I would say you have oil leaking into a cylinder and as long as you are prepared to keep topping up it won’t be a major problem anytime soon. 
But then again, don’t sue me😃

[Smoggy]

That depends on if the gearbox has an oil cooler, on my volvos the raw water goes through gearbox cooler then oil cooler then coolant heat exchanger then out through the exhaust so a couple of chances to mix with oil.

Edit: I see the mention of daily checks, does anyone actually do that on a private boat? I check mine every so often at best on the rivers and only regularly before a sea trip, no-one checks there car every day and they probably go further and rev it harder than most river boats.

[MauriceMynah]

I agree Smoggy, those "daily checks" are done on a "when I think of it" basis and I think I'm far from alone in this.

It's rather like life jackets. Everyone should wear one at all times... except perhaps me , because I'm careful.

[Smoggy]

Daily checks are a hireboat thing, when it's your own boat you know when something is wrong, especially when the bilge is not running with oily water.

[NeilB]

Do you have hydraulic drive?  Could be an issue with the hydraulic oil cooler.

[Oddfellow]

4 hours ago, Smoggy said:

Daily checks are a hireboat thing, when it's your own boat you know when something is wrong, especially when the bilge is not running with oily water.

Daily checks are a sensible thing to do. Hire boat operators want you to do these to prevent problems later in the day as, if you know you have low oil or water in the morning or a blocked weed filter, you can prevent a catastrophic failure later in the day. Daily checks are industry standard in many engineering environments are a reason. For the few minutes it takes, if it really worth ignoring them on your own, very costly boat?

[Cheesey69]

Yup, its the sea mentality. 

Plus the plant operator thinking.

On the Broads you kind of get into the habit of thinking your safe because you can see both banks!

Think about the length of time that old engine will run added to how far away from it you are. 

Four or five hours cruise will put you some distance if you was in a car driving around the UK. What the engine looses in miles it makes up for in time.

This is why I warm the engine up, no good finding out your weed filter is semi blocked or your engine thermostat is stuck closed mid river.