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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 11-08-2003
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Smokin'''' Perkins

I''m buying a 1980 Morgan 382, and have a couple of questions about the Perkins 4-108 that has about 2500 hours on it. The sellers say that they have maintained the engine well, and from looking at the engine both me and the surveyor tend to agree.

The sellers also say that the engine has never had any major work.

The engine does seem to idle a little high, but seems to run fine and scoots the boat along at about 6 knots at 2200 RPM, and at about 7 knots at full throttle.

There is, however, a steady and not insignificant stream of white smoke that comes from the engine whenever its running.

Should I be concerned? And if so, what''s your best guess? Would you have a diesel mechanic take a more in-depth look?

Thanks.
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Old 11-08-2003
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Smokin'''' Perkins

White smoke is usually steam, grey smoke is usually from burning oil and black smoke is usually unburned diesel.

I''d check for water getting into the combustion process from somewhere. A leaking head gasket is always a good suspect.

My 4-108 idles around 700 rpm.

Fairwinds,

Jim
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Old 11-08-2003
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Smokin'''' Perkins

White smoke usually occurs when there is not enough temperature to burn the fuel. The unburned fuel particles are then exhausted usually by a rich fuel smell. In cold weather it is not uncommon to get white smoke until engine temperature builds up. Low engine cranking speed can also create an excessive amount of white smoke.

If the problem persists after the engine is up to operating temperature several other things should be checked. A faulty injector can cause white smoke. Timing is often a factor when white smoke is excessive. Low engine compression can cause the problem and the injection pump can also have problems that result in white smoke. Air in the fuel system can also result in white smoke.

Lastly steam cause by a head gasket or other water leak into the combustion system can disguise itself as smoke. Steam will dissipate rapidly being once it hits lower temperature ambient air while smoke will persist and hand in the air.

Blue smoke is a sign of lubricating oil being burned by your engine. If you have blue smoke mainly at start up and it is very minor while running, this points to worn valve guides. When the engine sits for a bit (over night etc), oil left in the head after running can seep down into the combustion chamber. Upon start the bulk of it is burned quickly.

If you see blue smoke all the time when running, odds are you have a problem with rings or cylinders or both. All though sometimes a little solvent in the cylinders left overnight may free rings stuck up with carbon, usually, you will have to pull the engine and rebuild it to get things back to normal.
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Old 11-08-2003
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Smokin'''' Perkins

IMHO anyone buying a boat with a marine diesel should pay an engine surveyor to survey the engine, for the same reasons that you have a marine surveyor survey the boat itself. Like the boat survey, it is $250 (or whatever) very well spent. A reliable picture of an''s engine true health cannot be obtained from a one-time observation. Include a compression test.

The one thing a seller will not tell a buyer is anything the buyer really needs to know!

As an example, during our last boat purchase we had a mechanic test drive the engine prior to purchase, and he gave it an ok evaluation. We ended up with a full engine rebuild at the end of the first season, as difficulty in cold weather starting demonstrated low compression. This was a $10,000 mistake.

As the buy guys say "trust, but verify".

Good luck.
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Old 11-12-2003
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Smokin'''' Perkins

White smoke occurs as a result of combustion temperature being so low that only partial combustion occurs, and the partially burned fuel that exits the exhaust is in the form of a white smoke vapour. Technically, the white color is caused by the light-scattering characteristics of the re-condensed droplets of fuel (unburned or partially burned) larger than one micron.
Many factors contribute to this condition, including the following:
1. Poor fuel quality (low cetane rating).
2. Low inlet air temperature.
3. Low coolant temperature.
4. Low compression ratio.
5. Retarded (incorrect) ignition timing.
6. Incorrect/failed fuel injection components.
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Old 11-13-2003
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Smokin'''' Perkins

Where the white smoke possibly comes from is said already. But since all of this engines have a soule and their own specific little "faults", I thought I tell you a bit ab out the 4.108. The Perkins 4.108 tends to smoke a bit any way, no matter new or 5000 h what so ever. The smoke increases with the humidity. Fogy days, damp nights, it smokes, nothing to worry. If the engine is still smoking more than a bit on a dry hot summer day check the fuel lines first bevor you think of a major defect. A 4.108 gives you smoking signals on the smalest fuel leak, also the lift pump can be the leaking bitch.
How ever, this are easy things to check bevor you rip the engine a part.
I had one of the 4.108''s for ten years. It never let me down and I got used to a bit a white smoke and also a bit more on damp and humit days. I did a general overhaul on it after 5000 h. The engine was running a bit softer after, using less fuel and oil again but was still smoking white a bit.
Make shure your fuel lines are ok and no aer is goin in the system cause that''s someting this engine doesn''t like at all.

Still think of the advise having a disel mechanic to look at the engine bevor you buy.
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