A Little Over The Oil "FULL" Mark

[Joe Mullee]

I have a Yanmar 3GMF and over filled just a little bit when I changed the oil. I ended up removing the excess. Just curious, by over filling just a little could that have damaged the engine after prolonged use that way?

Just trying to learn something.

Thanks.

 

[Ross]

Not a problem. An extra quart would be another story but a cupful won't hurt a thing.

 

[Bill1565]

I ran that way for a couple of hundred hours when my dipstick broke at the hole those dopes punched in it to mark the full level. Needed enuff over to show on dip stick stub. Not only stupid, but there were no replacement dip sticks in this country. Had to wait on a slow boat from Japan. No apparent damage. I think it's a legend from the old days when additive packages were less sophisticated and oil "foamed".

 

[hman]

Actually, the danger from overfilling a crankcase whether it be a boat engine or a car is from the rods "slapping" the oil at speed. It will shake the bearings loose or actually break a rod.

 

[kendall]

Biggest issues with over filling is that it can reduce power output and foam up which reduces oil pressure.
Modern additives reduce foaming so that's not as big an issue as with old dino oils.

Oil pans are designed so the the crankshaft is never submerged, overfilling causes it to hit the oil surface and you lose a small bit of power each time a counterweight hits the oil. similar to rowing a boat, very little stress on the oar till it hits the water. The edge of a crank with a 3" stroke running at 2000 rpm is traveling at roughly 2500 feet per minute, so the slight drag adds up

It's why most motorcycles use dry sump systems, and nearly all modern cars are coming equipped with windage trays, simply to keep the oil off the cranks and reduce power loss.

A fairly common racing trick in the old days was to drain out about a quart to reduce the chances of oil hitting the crank

 

[Don12364]

No, No, a Thousand Times No (Old Vaudeville Song)

Overfilling with oil encourages foaming - worse if a modern detergent oil is used.
By law no crankcase is allowed to breathe into the atmosphere. So engine manufacturers achieve this by plumbing the crankcase breather into the air cleaner, often via a check valve.

So, the oil vapour feeds the engine and it runs on this regardless of whether it gets any diesel.
The faster it runs the more oil vapour it gets. This goes on until it either self destructs or some brave soul puts his hand over the air intake pipe of the air filter and strangles the engine.

My salesman pal was doing a pre delivery check on a brand new boat because the new owner was arriving in ten minutes. The engine had been overfilled and nobody knew. He revved it just to be sure and it ran away.

None of the yard's mechanics would go near it so it screamed its head off.
So the new owner arrived to an engine with a rod through the side of the crankcase.

 

[Sandy Stone]

Re: No, No, a Thousand Times No (Old Vaudeville Song)

You know, I've read here more than a few times that the way to stop a runaway diesel is to block the air intake, which is generally considered a little risky. Couldn't you just flip the decompression lever on engines that are equipped with one?

 

[Dan Johnson]

Sandy...

Flipping the decompression lever(s) should shut down a diesel pronto...

 

[JohnS]

Never having a diesel on board (mine's and A4), I'm not familiar with this issue, and wondering what the risk is in blocking the air intake. If using your hand, I'm guessing you might lose the skin?

 

[Hermit Scott]

Never having a diesel on board (mine's and A4), I'm not familiar with this issue, and wondering what the risk is in blocking the air intake. If using your hand, I'm guessing you might lose the skin?

I think they are more worried about getting fragged by an exploding engine block.

 

[Bill1565]

Re: No, No, a Thousand Times No (Old Vaudeville Song)

I shut down a Perkins 4-154 with the palm of my hand. Got a ring vacum moulded into my palm that went away in a few minutes. No lost skin cuts or anything.

 

[Rick486]

I shut down a Perkins 4-154 with the palm of my hand. Got a ring vacum moulded into my palm that went away in a few minutes. No lost skin cuts or anything.

I have also shut down a large perkins on a charter boat simply by placing a plastic dinner plate over the air intake. No worries about hand. The thing shut right down. It was not runaway though.

 

[Douglast]

Flipping the decompression lever(s) should shut down a diesel pronto...

if she is a runaway i wouldn;t depend on the decompression