Engine spraying oil at high RPM

Hi Everyone,

this is my first post to this site. I have read other threads about SBC spraying oil but so far i havent got the answer for my specific problem.

So what I have is a marine 383 stroker. This was a brand new engine (reman) from the factory. it ran very smooth for the first couple hours of use idling and up to 3500 RPM. once pushed to higher RPMs i got a warning sound that I had low oil pressure. I opened the hatch and the entire engine was covered in oil. Also since this time it no longer sounds smooth. it sounds like i burned up a ring or has piston slap.

the engine only looses oil when at full throttle. I have found oil in the intake.

Any thoughts on what this could be? i have attached the spec sheet for the motor as well

First, welcome to the forum. Glad to have you here.

A couple of questions that may help get you an answer. 1) Did you install the engine "as received", with no modifications like dress up parts? If you made any changes you need to explain them in detail; and 2) What did you do, and how long did you run the engine after getting the audible Low Oil Pressure Alarm?

I did install the engine as received with the exception of replacing all of the freeze plugs. It was supposedly dyno tested before delivery. I doubt the motor was dyno tested because upon delivery i noticed ALL of the brass freeze plugs were cracked.

The motor ran for about 10 seconds with the low oil pressure alarm. I shut it off, put a quart of oil in it and idled back to the dock.

I then took the motor out of the boat and checked the bearings on the crank and they didn't have any damage. I reinstalled the motor thinking maybe it was a one time event. i have idled the motor for about 10 hours of use over the summer but i have not ran it hard with the exception of one time when it did the exact same thing.

Time to check compression and cylinder leakdown on all cylinders------also what fuel and timing are you running---when an cylinder spark knocks, it rattles the rings off the walls and noisy, smokie, etc--------------

And check all of the venting including the venting of the engine bay

Welcome to CHR!

Like a lot of first time posts we get here you’ve got a nasty situation – sorry to hear about your problem but hopefully we can help you get this diagnosed and fixed to get that boat on the water this summer.

It would appear that pressure has built inside the engine to the point that it is literally blowing oil out where ever it can. Fortunately you didn’t get a fire out of this ordeal. Was there any indication of where the oil was coming out of the engine?

If this is a stock Mercruiser, your oil pressure alarm is probably on the same circuit as the engine temperature and transmission oil temperature. The oil pressure is a totally different sender and circuit. What was your oil pressure when you got the alarm?

What was your engine temperature when you got the alarm?

A compression check will tell us quickly if there is a bad cylinder (rings?) that is allowing that piston to be blowing the pressure generated on the compression stoke back into the crankcase. That would definitely be a problem and certainly account for your oil bath.

Did the PCV valve come out of the valve cover in this process? Does your PCV have a hose going into the air cleaner or the base of the carburetor?

Also, when you say the freeze plugs were cracked, did you contact the vendor you bought the engine from and ask why? I would see that as a red flag.

Keep the information coming and we’ll work this through with you.

Regards.
Glenn

I did perform a compression test. Cylinder 6 was low (135) and all others were around 160. I have not performed a leak down test.

I did contact the vendor (Mercury) about the cracked freeze plugs but they didnt even respond as this motor was sent to me free because I found out that the 1st motor I bought from them didn't have the forged pistons as advertised on the pamphlet i show in the original post. Im wondering if they didnt replace freeze plugs whats the chance they didnt do anything with the oil galley plugs as well?

The engine does not have any cooling issues and has always ran around 148-151 degrees. Its typical oil pressure is 45 psi at idle and at full throttle its pegged the gauge at 80 so I do not know how high it actually goes. My other 383 does this as well but has never had an oil spray issue.

when i got the oil pressure alarm it didnt show any oil pressure on the gauge.

The PCV valve did not come out of the valve cover and it does not have a hose going to the air cleaner.

for the life of me i cannot figure out where the oil is coming from when it blows everywhere. there is so much all over then engine bay but non on the engine itself.

Can you post some pictures? It's possible there's a oil galley compromise and a stream of oil is escaping under pressure.

Is it possible to observe the engine when running or is it under a complete cover?

The 80 psi may or may not be a problem. What oil are you using? I'd use 5W-20 until the bearings clearance themselves - probably the first 10-20 hours of run time.

I'd also hook up a temporary mechanical oil pressure gauge - you can "T" off the top/rear of engine behind intake (1/8" pipe thread) or above oil filter there's a 1/4" plug - just to verify the reading on the stock (electric) gauge.

Let's keep after this - others will chime in I'm sure.
Glenn

Quote:

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Originally Posted by axm0z5h

The PCV valve did not come out of the valve cover and it does not have a hose going to the air cleaner.

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You say that the PCV didn't blow out of the valve cover, but more important that it does NOT have a hose from the PCV to the air cleaner? What is hooked to the hose connector tube on the top of the PCV? The hose to the air cleaner, or to the base of the carb provides the vacuum pull to evacuate the crankcase, and without a hose that pressure will blow out through the PCV like a demon. That could be the source of your problem.

At 80 plus psi it wouldn't surprise me to hear the oil is spraying past the oil filter seal.

Here are some pics of the engine and around the intake.

The PCV valve is on right rear valve cover with the hose going to front of the intake manifold. The vent hose on left rear valve cover with the hose going to air filter intake.

Too bad you can't put a gopro or similar camera under the compartment lid and go give it a wack or 2 on the water. does your oil fill cap have an o ring on it? Is that a vented cap? I've seen some of those on some BBC boats and they have an orifice drilled through the top edge to the center as a vent. My friend had a massive Baja with 2 502s and it kept blowing oil out after he had the engines replaced. A guy down at the Lake of the Ozarks showed us the fill caps. He swapped a pair from his boat and the problem went away. After that he heard of others having similar issues too. I'm not sure if it was an incorrect shipment from a supplier or what. I'm not sure if that is your problem but it is something to look at.

Ill take a look at that cap. I cant remember what type it is.

I do have a go pro and was thinking of doing that. whats stopped me is having to clean the bilge out again lol.

Quote:

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Originally Posted by axm0z5h

Ill take a look at that cap. I cant remember what type it is.

I do have a go pro and was thinking of doing that. whats stopped me is having to clean the bilge out again lol.

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I can understand that. But it would help you see where the oil is coming from. A leak down test would give some good info too. Maybe the rings aren't seated in yet and it's got excessive blow by and it pushes the oil out at higher RPMs. Or maybe for some reason the oil isn't draining down to the lower end fast enough and the oil gets forced out somewhere at the top?

Well I took the boat out yesterday and got on it for a few seconds. I had my friend video the engine. As you can see it was coming from the dipstick and onto the alternator which was why it was flung all over the place.

https://youtu.be/WKNSOOO7E6M

Thanks for coming back and sharing the results of your video. It's good to know what was the problem.

Is that dipstick one of the sealed / locking types? Hard to tell in the video.

any engine will blow the dipstick if not vented well enough. i mistakenly use the push in caps with no holes on a 302 ford engine. all it had was a pcv valve . it blew the dipstick and oiled down the engine. i now run moon breathers on every build. they releave crankcase pressure well enough i have dry engines . i would try better evac first before i tore anything down .

some boat engine dipstick tubes go all the way down to bottom of pan so oil can be sucked out on oil changes--------buttttttttttt---------then , if the engine isn't vented properly and/or some excessive blowby--------it will pump oil out the top---

The dipstick doesn't lock. It just pushes in. I'm going to take a look at the PCV valve this week. It was new when I installed the motor.

What are your thoughts on my oil pressure? 45 at idle, 60 at 1500rpm and 80 psi from 2500 rpm and up.

i'm not really a wrench but i have always gone for volume instead of pressure . if a pcv is all it has it will always leak. you need a good evac on a boat . they normally run on the high end of rpm and oil is sloshed around the pan . i would drill and tap those screw in valve cover caps and run a hose to a recovery tank. an old mech i once knew would say engines only leak at the drain plug, everywhere else is blown out by crankcase pressure.

If you can, verify that your pcv is working and that the opposite valve cover has a breather.
A pcv valve only "pulls" at lower throttle settings, so you'll need the vent on the opposite side to allow air in as well as allow pressure out at w.o.t..

If you aren't blowing off the oil filter at 80 psi (and above?) then run it.

# 6 cylinder low compression is pressurizing the crankcase forcing oil up the tube-------boat engines are configured with an oil dip stick tube that goes all the way to bottom of pan so during an oil change you can pump the oil out of the pan into container---------in some boats you can't drop hose out thru bilge drain hole to change oil-you PUMP it out the top---------

im going to spend some time on this week checking into everyone's suggestions. I will report back with my findings. Im hoping that all I need is some new rings and PCV valve

I don't think I'd jump to rings too quick - you only have a few hours on the engine and the rings do need to seat. PCV valve is an inexpensive item and easy to change. Do you have a vent in the opposite valve cover? Also, you may want to consider a sealing/locking dipstick like this:

https://www.speedwaymotors.com/Lokar...ick,67748.html

There are a lot of vibrations in a boat so a different dipstick may be appropriate.

Thanks for keeping us posted - the video say a lot and is extremely telling.

Best,
Glenn

Well what has me thinking about the rings is a whole other issue. I have two of these motors. They both make the same noise but the 2nd one didnt make the noise when I first installed it. It only made the noise after it blew the oil out, but prior to blowing the oil the engine ran as quiet as a new car.

I was thinking that the piston skirt is really short and it has pressed in wrist pins. maybe the piston is rocking back and forth and hitting the skirt?

here is the noise that it makes.

https://youtu.be/xLl9AkFy_eY

Quote:

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Originally Posted by glennsexton

I don't think I'd jump to rings too quick - you only have a few hours on the engine and the rings do need to seat. PCV valve is an inexpensive item and easy to change. Do you have a vent in the opposite valve cover? Also, you may want to consider a sealing/locking dipstick like this:

https://www.speedwaymotors.com/Lokar...ick,67748.html

There are a lot of vibrations in a boat so a different dipstick may be appropriate.

Thanks for keeping us posted - the video say a lot and is extremely telling.

Best,
Glenn

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I think ill get that dipstick.

IMO the locking dipstick would just lead to blown seals. I'd make sure it breaths well first.

Quote:

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Originally Posted by 40FordDeluxe

IMO the locking dipstick would just lead to blown seals. I'd make sure it breaths well first.

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So i just checked the PCV valve. The valve covers do not have a baffle in them however the stock ones did. I am going to install baffles. also there was a ton of buildup on the PCV valve most likely from condensation. im pretty certain it wasnt operational.

Well i never found out what the issue was. I had an intake gasket fail last week and filled the motor with water so I took it out and swapped in my other motor.