Your going in right direction. You'd see the oil cloud if it's going out the exhaust

 

thats been my thoughts... that and the temp thing would explain why i dont see it at idle in the water

 

Is there a sheen or spots of oil at the exhaust? Pull your hose off that oil cooler if it’s leaking that much you will see and feel it.
Older boats with side exhaust, you will have a black mess on the hull by the water line.
What is the hours on the engine?
My guess is valve guides and seals.

 

Is there a sheen or spots of oil at the exhaust? Pull your hose off that oil cooler if it’s leaking that much you will see and feel it.
Older boats with side exhaust, you will have a black mess on the hull by the water line.
What is the hours on the engine?
My guess is valve guides and seals.

just over 600 hours on it. dont see any thing in the water, which is leading me to the heat/pressure theory

if a compression test doesnt show anything i guess i'll pull it out of the water and do a leak down.

 

Oil doesn't pass through the head gasket, only water. Was also thinking that if it was going out your underwater exhaust may be it wouldn't smoke.

 

how does the oil drain back from the heads down to the block? every motor short of a dry sump set up has oil passages that drain back from the head to the block

 

All oil drains directly into the lifter valley, has nothing in the head gasket for oil

 

well shit... so much for that idea

 

Have to read all the plugs? They must show oil on them or the oil is being pumped out of the oil cooler.

 

Well plugs show no oil... 1 hole is running a bit fat
All holes pump 140-150psi

New oil cooler is in and oil topped off. Going out this weekend so I'll report back

 

Welp... Still losing oil

 

With that much oil being lost there has to be a really big smoking gun

 

This was cruising back Saturday night

 

Do you have any photos of the plugs?

If it isn't the oil cooler and the bilge isn't filled with oil.....the engine is pushing it out the exhaust.

I have seen dipstick tubes and senders come loose and will easily pump the oil into a part of the bilge that is difficult to see.

 

And the motor runs good... Right?

 

How much and at what rpm? What year and total hours on this engine

 

What weight oil are you using?

 

20w50

 

Not seeing anything in the water as far as a sheen or spots.

It's a 98 with 613 hours currently.

Cruising around 3800rpms roughly a qt an hour.

Didn't get pictures of the plugs but from years of running 2000hp race cars Im pretty good at looking at spark plugs. And I didn't see anything that had me worried. I do have 1 hole that's got too much fuel. But I'm going to switch out that injector

 

Not seeing anything in the water as far as a sheen or spots.

It's a 98 with 613 hours currently.

Cruising around 3800rpms roughly a qt an hour.

Didn't get pictures of the plugs but from years of running 2000hp race cars Im pretty good at looking at spark plugs. And I didn't see anything that had me worried. I do have 1 hole that's got too much fuel. But I'm going to switch out that injector

Okay...no plug pictures, compression is okay, oil cooler replaced, no oil in the bilge and it is still using a quart of oil an hour. The only thing left is the engine. I'm not sure you would see oil on the water at cruise. Oil pressure builds with rpms and the amount of oil under the valve covers dramatically increases which if the valve seals are the issue would explain why it doesn't show up at idle or no wake speed. That said....if it was the valve seals/guides.....there are usually tell tale deposits on the plugs. And if that wasn't enough...the valve seals would have to be almost completely ineffective to burn a quart an hour.

It just seems like we are missing something.

 

im going to try and get some free time this weekend to pull the 1 injector out of the hole thats running fat and put one of the older injectors in there to clean up the 1 hole thats running fat.

im going to try and borrow a friends small air compressor to do a leakdown on it also my compressor is just too big to drag out on the pier.

and i agree 100%... im missing something

 

I quart or oil in an hour.......
If you’re in the mid 3k rpm range, probably burning about 15gal/hr gasoline.

15 gallons of gas to 1 quart of oil is a 60:1 ratio. Is it possible that it is a relatively small amount of oil and can burn off without fouling the plugs or showing any signs of oil contamination?

I know losing 1 quart per hour is a lot and not knowing the source is frustrating.

 

1 qt / hour burning thru cylinders would result in visible blue smoke for sure . check the bilge twice and then check it again for an oil leak .

you would also have a severe blow by from dead cylinders . when you remove the oil filler cap with engine running - does it blow severy out of the oil filler cap ?

if not you are not burning this oil.

 

I had that kind of oil coming from a valve cover. It was "hidden" and I only found it when a put my hand on it to pick something up. So I would start looking in hidden spots. Good luck.

 

ive thought about degreasing the motor and seeing if anything pops up that i see

1 qt / hour burning thru cylinders would result in visible blue smoke for sure . check the bilge twice and then check it again for an oil leak .

you would also have a severe blow by from dead cylinders . when you remove the oil filler cap with engine running - does it blow severy out of the oil filler cap ?

if not you are not burning this oil.

never thought to run the motor with the cap off... but i'll check that thursday when im down there. i want to hose the bilge out and get everything cleaned up in there. i forgot to put a bucket under the raw water hose when i pumped all the sand out of the motor after hitting bottom. so i still gotta get all that out of it.

so far ive put right around 18qts in the motor in the last 3 weeks... feel like id see it in the bilge by now if it was there.

 

Worn Exhaust guides or valve seals will pass a lot of oil and you will not see it on the plugs.
Is this a new boat to you?

 

My engine is the same year and the manual states that the engine will use 1 qt. of oil in 1-5 hours of running at or near full throttle.

 

really? that seems crazy

 

Crazy high ? Also says that oil consumption will be a lot less at moderate speed

 

yea im reading it now... 1qt every 5-15 hours under lower RPM range.

 

the 7.4 mag has forged pistons . Just had my motor freshened up and the machine shop ordered oversized rings and file fit them, I do say I'm using quite a bit less oil than last year. Using half of what you just mentioned