Burning oil off engine smell

Technologic80 · **Posted:** Mon May 11, 2015 1:01 pm

I brought my 278 Vista for a cruise the other day, the lake was calm so I "stretched my arm" a little and was cruising around 4500rpms, going about 40mph. Oil pressure great (fresh oil change), temps great (160-170). Came off plane and it smelled like I missed the oil fill and spilled oil on my engine - but I had not. As a matter of fact, I changed the oil last fall, and when I was reconnecting all of the water hoses last week, there was no oil or anything to speak of on the valve covers or anything.

The smell is definitely coming from the stbd engine. Oil levels are perfect, on the button. There is no oil in the bilge. I did some google research on the

Is it reasonable to assume that after 18 years, my valve cover gaskets might be seeping some oil? Any other suggestions?

ric · **Posted:** Mon May 11, 2015 1:54 pm

There's nothing on a marine engine hot enough to burn oil on the outside (hopefully). What you're smelling is most likely blow by. Rings are getting worn out and pushing oil vapors out the oil breather.

LouC · **Posted:** Mon May 11, 2015 3:57 pm

Interestingly enough my original '88 valve cover gaskets still do not seep oil. Back in the '70s when we had a '72 Chevy Impala that we bought new the OE stamped steel valve covers and cork gaskets ALWAYS leaked on these engines, (ours was a 350) so they at least fixed that problem. It could be as ric says, take a look at how much blow by you're getting. The thing with a marine engine is that if they were seeping, its going to be hard to see it because the exhaust manifold is in the way. When I had my manifolds off a few years back they were dry.

ric · **Posted:** Mon May 11, 2015 5:22 pm

The exhaust manifolds do not get hot enough to burn/smoke oil on a marine engine. Leaking valve covers would just get them oil soaked and prevent rust.

Technologic80 · **Posted:** Tue May 12, 2015 4:02 pm

Interesting.

My stbd engine has 219 hours on it... has been used gently and maintained impeccibly. I find it hard to believe I have blow-by already. But I suppose anything is possible. :?:

Also when I cleaned my spark arrestors last week, there wasn't any oil on the spark arrestor. I am going to go out there in a little bit and feel around the engine block. I still think I have an oil leak.

alex8q4 · **Posted:** Tue May 12, 2015 6:23 pm

In my opinion blow by does not smell the same as oil burning on a hot surface.

Having said that I am with Ric in thinking nothing should be hot enough to burn oil.

Could it be the smell of a hot bearing on a pulley or in the alternator?

deafwish · **Posted:** Wed May 13, 2015 2:12 am

Plenty of components on my engine get hot enough to burn off a lubricant.
Spray your engine with a corrosion inhibitor (WD40) and take it for a WOT run.
I bet my left nut it will stink and smoke like hell!
Ric - take a photo of your finger the next time you touch a header bolt after a hard run. :wink:

alex8q4 · **Posted:** Wed May 13, 2015 6:34 am

Well, we happen to spray the 350 in our lib with WD-40 for winter storage...

It does not smoke like hell in the spring, but please keep your left nut.

ric · **Posted:** Wed May 13, 2015 9:04 am

The hottest part of the exhaust system in the engine bay should never see above 180 degrees after a WOT run. Normal exhaust manifold temps are around the 160 mark. That's not hot enough to smoke motor oil. You should easily be able to touch your exhaust manifolds when the engine is running without getting burned for a few seconds. If you can't touch them, time to see a mechanic.

rpengr · **Posted:** Wed May 13, 2015 2:30 pm

deafwish wrote:

Plenty of components on my engine get hot enough to burn off a lubricant.
Spray your engine with a corrosion inhibitor (WD40) and take it for a WOT run.
I bet my left nut it will stink and smoke like hell!
Ric - take a photo of your finger the next time you touch a header bolt after a hard run. :wink:

I spray Boeshield T-9 corrosion inhibitor anywhere and everywhere on my engine, including the manifolds, and it does not burn off.

Technologic80 · **Posted:** Wed May 13, 2015 2:34 pm

With all respect, deafwish said after a WOT run, you might smell burnt wd-40, or oil. The day I ran the boat close to WOT. My temperature gauges on both engines are always pretty happy at 160-170 degrees.

I never did get down in the bilge to check for oil on the sides of the block. All I know is I definitely smelled oil. It wasnt exhaust-burnt oil, like from an old worn out car kind of smell, it was the "I just missed the oil fill and dumped 1/2 quart of oil somewhere on top of the engine" kinda of smell.

ric · **Posted:** Wed May 13, 2015 2:43 pm

Technologic80 wrote:

With all respect, deafwish said after a WOT run, you might smell burnt wd-40, or oil. The day I ran the boat close to WOT. My temperature gauges on both engines are always pretty happy at 160-170 degrees.

I never did get down in the bilge to check for oil on the sides of the block. All I know is I definitely smelled oil. It wasnt exhaust-burnt oil, like from an old worn out car kind of smell, it was the "I just missed the oil fill and dumped 1/2 quart of oil somewhere on top of the engine" kinda of smell.

Well to be fair, your motors are 18 years old they're not spring chickens anymore. Things wear out with age too, not just hours.

rpengr · **Posted:** Wed May 13, 2015 3:08 pm

All engines have "some" blow-by, even new engines. However, the blow-by is led into the intake manifold to get burned up and exhausted out with the rest of the exhaust. The route to the intake can be in the form of a PCV valve, or a simple vent hose attached near the intake flame arrestor. A split or broken hose, or a bad PCV valve could cause your smell.

ric · **Posted:** Wed May 13, 2015 3:16 pm

If you have enough blow by to smell oil fumes that's not normal. That's a red flag for worn out rings.

deafwish · **Posted:** Wed May 13, 2015 4:18 pm

Older carb'd intakes will have an exhaust crossover that gets red hot.
Exhaust manifold bolts will also get red hot.
Just stating some facts in an attempt to float the concept that your engine might not need a rebuild due to excessive blowby!

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Burning oil off engine smell

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