OT - blow by - not mercedes

[daverdla]

I'm looking at a boat with ford/lehman diesel engines. I had a diesel mechanic look at it, run it, test it, etc. He said that the engines are fine. He also measured blow by and found both engines to be well within spec. Another mechanic said the blow by was high, just by feel at the dip stick, resulting in unburnt lube oil getting past the rings into the combustion chamber and out the exhaust without being burnt - no blue smoke. In fact no diesel smoke. The whole topic came up because it was thought that there were a few drops of oil coming out the exhaust - this may or may not be true - if it is it's usually an oil cooler leak.

Anyway my question - can lube oil can pass the rings and go out the exhaust without being burnt. This engine ran like a top and started instantly. It was without question running on all 6 cylinders.

One thing I noticed about most of these boat diesels - no glow plugs. This particular engine has a cold start valve that you pull prior to starting - it allows more fuel in the combustion chamber. I wish I could put a couple of 3.0L turbo diesels in the boat.
Thanks
Dave

[tenknots]

Those Ford Lehman's are great engines. I can't imagine lube oil getting into a diesel cylinder and not getting burned. The "oil" out of the exhaust might be soot that mixes with the cooling water. Did it leave a sheen on the water? Even then, it might be a bit of unburned fuel from a cold start. If there is oil coming out after it's warmed up, there may be a problem. It could also be an oil cooler leak - if so, fix it quick, it's only going to get worse and you don't want to be throwing oil in the water anywhere near law enforcement. It can also cause the engine to lose it's lube oil.

My sailboat's 4-cylinder Perkins engine has no glow plugs either, nor a cold start. Has some kind of wonky air filter heater that doesn't work. I started the boat a couple of weeks ago for a day trip and it started right up in 35 degree weather, even though it hadn't been started in a year.

I've often thought of putting in a 240D engine, but these industrial engines like Perkins and Lehmans last forever. They tend to be a bit noisy, but I kinda like the sound.

I helped a friend inspect a Hinkley 49 a couple of years ago and it had a 5 cylinder turbo Mercedes engine. The finest diesel engine in the finest sailboat - how fitting!

[TwitchKitty]

Boat engines live a way different life than automotive engines, running relatively little but at constant speeds and high power output in a corrosive environment. Corrosion is likely to cost you more than wear. People often unnecessarily throw money at boat engines in the form of unneeded rebuilds to replace unworn parts.

Do a leak down test and check the oil pressure. Take a very close look at the cooling system, exhaust manifolds, check for corrosion. Look for leaks.

Check the fuel system for water.

Check the boat for access to components for maintenance. Consider that the boat may be rocking with the waves when it breaks down somewhere.

[daverdla]

thanks guys. I really think it's more likely to be the oil or tranny cooler too. Oil going past the rings and not getting burnt doesn't seem possible in an engine that runs perfectly.

I kind of wish it did have a couple of 3.0L mercedes turbo diesels!

Dave

[psfred]

No glow plugs means it's a direct injection engine (typical of US manufacture). The oil cannot go past the rings and out the exhaust without being burned unless the cylinder isn't firing, and you would notice that.

Cold direct injection engine (especially low compression ones) will "wet stack" -- what you are seeing may be unburned diesel. If so, it will smell of fuel and leave an oil sheen. I suspect what you are seeing is carbon (soot) and condensation in the exhaust from a cold start.

You should fix that pre-heater, it makes the engine start MUCH better. Avoid ether (although I suspect you won't be starting boat engines at extremely low temperatures anyway, for some reason....!) as it can pit the piston crowns.

If it starts up instantly stone cold and doesn't smoke or puff blowby, it's fine.


Peter

[D240]

was the blow by tested under load or at idle ? if it passes under load all should be well. wet stacking is common in those engines especially if the heated air intake isn't working.

[Hatterasguy]

How many hours and what year? These are very hardy engines, Grand Banks used them for years. I would also get the lube oil tested, it will only run $30 per engine and could tell you a lot.

Engines can be rebuilt I wouldn't pass on a nice boat with tired engines if the price is adjusted accordingly.

[daverdla]

The blow by was tested under load. The mechanic said that if the blow by measurement was within spec, there wasn't any reason to do a compression test. It the blow by was too high, he'd have to dig deeper. He also found that the starboard engine, which is new, had more blow by than the port engine (I'm saying the engine is new but it's actually around 5 years old with very few hours on it). Blow by was well within spec. He felt that the starboard engine wasn't yet broken in. I got the break in procedure for it and will follow it. I hope it's not too late

The engine in question, port side, is only showing 617 hours. I doubt it's correct but it could be. It's a thirtyone year old boat and the port engine looks original but it may have been replaced. We didn't get the oil tested. Both engines had their oil changed when they were winterized last fall so there wasn't any run time on them. We're finalizing the deal this weekend and taking her home the following weekend.

It's also got a little Onan generator. Glow plugs are on the generator. To start it, you hold down a momentary switch for 30 seconds before cranking. No timer.

Strange not having all those vacuum lines.