Problems with inboard diesel.

[Birvidik_Bob]

We've just motored down from Gouvia to Lefkas (no wind). Toward the end I noticed that the oil pressure had dropped significantly, to barely within the limits advised in the manual.

I looked in the engine bay but no signs of oil loss. Thinking that we might be burning it I looked at the exhaust and it was definitely a lot smokier than usual, but apparently white rather than blue.

there are no noticeable differences in sounds from the engine and it seems to be developing as much power as usual.

Any ideas as to possible causes? It's a Mermaid Melody 4 cylinder naturally aspirated (essentially a Ford New Holland tractor engine).

Grateful for any suggestions.

 

[chrishelen]

Stop the engine let it cool and check the oil level would be the first thing i would do,if its ok when did you last change it?White smoke, is the cooling water looking ok, does the oil look milky? best of luck.

 

[Chris_Robb]

Hi Bob - I like your new identity!

If the oil level was low, I think the guage would appear to flutter as it picked up some oil then failed to pick up. So if it is steady at a low pressure, it is unlikely to be due to not picking up oil.

If you start the engine from cold, does the oild pressure start high and then drop off?

The old mermaid engine had the injector leak off returns to the tank, inside the rocker cover, so my bet as to what is happening, is that you have a crack in one of the leak offs and you have lots of diesel in the oil.. If the engine does not loose oil on a normal basis, you should see the level much higher. The oil will also look thin. I suppose the quickest way to proove this, would be to change the oil. Then if the pressure is then OK, look at the leak offs in the rocker cover.

Good sailing - hope to get to Greece next year -

regards

Chris Robb

 

[aluijten]

Are you using the correct oil? If the oil has incorrect viscosity than it may become too thin when it becomes hot. I have no knowledge of your engine but it might be a case of too modern (synthetic) oil in a engine that expects oldfashioned semi-synthetic oil.

Arno

 

[oldsaltoz]

White smoke sounds like steam, probably from a long run and heat build up as a result.

 

[charles_reed]

I would suggest that the most likely is a small head gasket break between oil and coolant galleries.

Check if there's any oil in your coolant, to put that one to bed.

 

[TQA]

You are VERY unlikely to get oil in the coolant. But diesel in the oil is a common problem.

One off the wall source of diesel is a leaky fuel lift pump. If you have a fuel pump mounted on the side of your engine and it is driven off the camshaft [ from memory that is the situation with that engine ] you can get a leaky pump diaphragm AND a blocked drain hole [ usually paint ] feeding diesel into the sump. Result thin oil.

 

[boatmike]

The old mermaid engine had the injector leak off returns to the tank, inside the rocker cover, so my bet as to what is happening, is that you have a crack in one of the leak offs and you have lots of diesel in the oil.. If the engine does not loose oil on a normal basis, you should see the level much higher. The oil will also look thin. I suppose the quickest way to proove this, would be to change the oil. Then if the pressure is then OK, look at the leak offs in the rocker cover.
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You are indeed correct and its one possible cause. However, if that were the case oil levels would be high, but not necessarily very high. Changing the oil is a good plan anyway in these circumstances, but when you do check the level to see if it's higher than you normally keep it. Of course it could simply be old age and bearing condition. Check the pressure when you first start up from cold. If it's OK then and only goes down when the engine has run for a while it's simply general condition. If you have diesel diluted engine oil it will be low when cold. If when hot it's still within the normally expected limits but lower than when cold it's not too much to worry about now but probably a warning that at the end of the season it needs some TLC or even replacing.....

 

[seaesta]

White smoke on a diesel is usually unburned fuel (as opposed to part burned fuel which is black smoke) This can be a cylinder not firing or fuel vapour leaking or fuel vapourising on a hot surface.
Martin

 

[charles_reed]

many would disagree with your white/black smoke comparison - besides the man goes out of his way to say no reduction in power.
though no comment about oil-level - funny that's the 1st thing I'd look at.

I'm afraid we're all guessing with insufficient information to make it statistically significant.

Perhaps Birvidik Bob you'd like to give us a little more info like:-

1. Is the oil level up to mark? All the symptoms you've described could be down to having forgotten to top up.
2. Is the oil contaminated? ie thinned with diesel or mixed with water.
3. Any oil in the coolant (For so-certain I've known it happen twice with Yanmars) or is coolant level down.

Then we can all stop shooting in the dark.

 

[Birvidik_Bob]

Thanks for all the suggestions so far. Unable to check oil level & condition so far as engine still too hot (have to lay in small space directly on top of engine). Will do those tests tomorrow morning when it's cooled down.

The engine's run a total of 1100 hours and has been serviced as per recommendations in manual. It's only done 11 hours since oil change. Ran well for the first 8. Oil is right type etc. Have just had injectors serviced.