smoking exhaust with newish diesel

P

pW2

Active Member
Joined
19 Sep 2005
Messages
53
Visit site
I bought a small motor boat some weeks ago with a Vetus/Mitsubishi 3 cylinder motor with 400 hours running. But the motor has not been run for the last 4 years or so. There are a couple of problems if any one can help I`d be grateful. So far I`ve put another 90 hrs on the clock which seems to be accurate. At 2000 rpm she cruises at 5 knts and uses 2 ltrs/hr, though on one 8 hr trip she used 3 ltrs/hr (consumption is measured by dip stick, which is quite accurate, especially as I keep the tank fullish and measure in much the same place in the tank).
The exhaust is smoking quit a lot, sometimes more than others. The injectors have been removed and checked, all good, the tappet clearance has been checked and is OK. The other problem is engine oil which seeps out of the junction between crank case and gearbox, not a lot but after 8 hours running something like half a cup. Presumably the crank case oil seal isn`t working properly and the leak will only get worse.
Is it possible the two problems are related? Just how difficult would it be to replace the oil seal?
Peter
 
Well, it may be that the seal needs replacing although it sounds a bit marginal. May be wrong, but I suspect you're getting excess pressure in the crankcase which is blowing oil past an otherwise OK seal. The fact that the engine was stood for years could have caused the rings to stick in the piston grooves, although obviously you're getting sufficient compression to start and run, a bit of blow by can pressurise the crankcase. Not being familiar with that engine, I'd check the pressure relief first as that could be where the oil is actually escaping (as it should). Many engines have the relief pipe fed into the intake manifold, so that the engine consumes the oil mist, but if the hose has come adrift it will spray out. Worth a look, anyway. The effectiveness of long-term solutions are more difficult to predict, I've known people to successfully free the rings by pouring diesel into the cylinders to soak through the gummy deposits. In fact, regular running may clear the problem, but I'd expect it to have done so by now. If it persists you'll just have to bite the bullet and strip down to clean up the pistons, maybe change the rings and you may as well fit a new oil seal whilst you're doing it. It's the cost of gaskets that make such repairs expensive.

There's a nagging thought at the back of my mind that someone suggested a better solvent than diesel to clean the pistons. Let's hope they come back to advise!

Rob.

P.S. Should have called it a crankcase breather, shouldn't I? If the rings are sticky, then on suction stroke oil vapour can be sucked up into the chamber.
 
Last edited:
What colour is the smoke? Brake fluid can also free rings, or redex. Its really easy to change the oil seal, its getting the gearbox and engine split to do it! Just depends on the room around your gearbox. Also does it only smoke when cold or all the time?
 
Is it smoke or steam? did you replace the water pump impeller? as above, what colour is the smoke / steam, how were the injectors checked? did you fit new sealing sleeves/rings when refitting the injectors?

Redex can help free off stuck rings.
 
If the smoke is blue your burning lub oil, this will also have a sickly sweet smell. Black smoke and you have got incomplete combustion. Usually a dirty air filter is the cause but it can be a dripping injector or even the injector pump metering. White smoke is actually steam and is water/moisture entering the system. Grey smoke may be crappy fuel.
The oil seal whilst easy to change will entai a heck of a lot of work and discomfort to access.l
 
You might like to try a fuel additive. Since this time last year I have used Marine 16 Diesel fuel Complete, which claims to keep the fuel system clean as well as protectng against diesel bug. I can't say its had a big affect in my case as the decision to use it was for prevention rather then cure. But I think the engine seems to run a little smoother. I still get a few whips of smoke on a cold start but it quickly disappears. (It is not the same engine as yours by the way).
http://www.marine16.co.uk/acatalog/Fuel_Treatment_Products.html#a59

On your engine is there a crankcase breather with a filter ? If so consider fitting a new filter.
Also consider fitting a new air filter. Mine was quite grubby when last changed after about 90 hours run.
I dont know what your engine maximum speed but it might be worth giving the boat a good run at say 80 to 90% of maximum recommended revs, if you are able to do so without breaking any speed limits. I do a lot of slow speed running and my engine always runs better after it has had a good work out.

.
 
As always the forum has come up with all sorts of usful info, many, many thanks. I`m in France at the moment where Internet connection is even more difficult than Ireland, but I`m in a marina at tne moment and should have conection for the next day or so. So if you have any further thoughts I should be able to read them.
This engine does NOT have an intake air filter.
The smoke is a very pale grey to white. It doesn`t have any real smell, at the moment but it comes and goes.
I cleaned out some fuel I thought was dodgy and have been making sure only clean fuel goes in the tank, using bottles so I can also get a proper measure for the Redex I`ve been useing, but Redex wasn`t available here so at the moment Star Tron (which seems to be more an enzyme treatment than system cleaner) is going in with fuel.
The injectors were checked at a company specializing in the things. New copper washers, provided by the company were fitted.
Raw water impeller, oil and fuel filters replaced when tappet clearance checked as part of 400 hr service.
As far as I can see there isn`t a crank case breather filter. At first sight I can`t even find a breather. Any reason why I shouldn`t leave the oil dip stick out and see if that makes a difference?
The plan is to head off south after celbations of the 14th and I`ll certainly use more revs than usual
Peter
 
White smoke means they've elected a new pope.

As a starting point I'd renew all the consumables, impellers, filters, fuel and oil. You don't say if it's a turbo, I assume not, but if it is you need to check all the electronics, check for leaks, check the turbo vanes etc etc. If a standard diesel try injector and fuel system cleaners, they sometimes work. You might just need to run it a while longer till the valves bed in and the rings seal again.
 
Check you have no water or moisture collecting in filters and the bottom of the storage tank. Bad fuel running through the system might also be audible as well as producing greyish smoke. As water does not burn you might be able to hear a little stutter every rev. On the plus side it will cool combustion and lower your emissions which will keep the EU happy. Do you think the bad fuel was loaded bad or became bad onboard? It might be worth checking you filler cap o-rings or any inspection hatch gaskets.
If your measuring consumption by means of sounding the tank then ensure the vessel is in the same trim each time. You would be amazed how much being down by the head/stern or a pt/stbd list can effect tank soundings.
 
It may appear too simple but a badly seated oil filter has led to many engines being stripped down,always worth checking for leaks.
 
I think rob2 in post No 2 is nearest the mark
However, before you start spending cash on additives it could be worthwhile getting a compression tester to see how much it is down. Whilst this may be a bit inaccurate in values, or you may not know what value to expect, it may show up one piston compression as being lower than the rest.. You then know why you could be getting higher crank case pressure etc
You could then try soaking oil or redex etc in that piston for a while. It will also show if adatives are working
A 3 cylinder engine is not that big so at the end of the season get it out & either do yourself or get it reconned
 
You must log in or register to reply here.

Other threads that may be of interest

jamie N
Chinese heater exhaust 'insulation smoking'
Replies
13
Views
701
Dellquay13
Dellquay13

Share this page

Top