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sparky344
02-21-2006, 11:00 PM
"1990 Merc 454

2nd time this season out on the lake, noticed on both runs that I have maybe 1/2 an ounce of oil on the floor under the dipstick, seems to be coming out from just under where you grab it to check level .... potential causes?

There don't seem to be any performance changes, still able to run 55-58 mph. Engine oil is due to be changed. Oil pressure gauge shows 90-100 psi."

Harves Marine
02-21-2006, 11:14 PM
"Usually thats excess crankcase pressure or blow by building up. It has to go some where and sometimes up the tube. Is there a bit of oil getting on the flame arrestor? Does is smoke out the valve covers at idle badly? This would indicate bad rings and blow by, OR too much oil in the engine, that oil pressure seems too high."

federicob
02-22-2006, 10:32 AM
Maybe the oil is coming from some other place and dripping by the dipstick. I had a problem of oil coming from the valve cover where the tube that recovers the oil gases is inserted. The rubber plug was leaking.

Have you checked the oil level for changes?

pedlyr
02-22-2006, 11:00 AM
"Many dipsticks have a seal or O-ring where they meet the pan, and they do like to leak. If you think your leak is higher, sometimes a bent stick will not seat in the tube properly and can leak."

fastjeff
02-25-2006, 10:42 AM
Also check out your PCV system.

Jeff

scottc
03-10-2006, 07:42 PM
"I Had this problem on a Merc model 470 4 cylinder. Turned out to be a craked piston. Excess crankcase pressure obviously. Hopefully, you dont have the same problem. $$$. That was lots of oil coming out as well. BTW 90-100 oil psi is WAY TOO MUCH, check your sending unit.

Hope this helps,

Scott"

sparky344
04-13-2006, 10:11 AM
"Just an update, I have two oil pressure gauges. The electronic one on the dash must be shot, the mechanical gauge at the engine is reading 40 psi at idle. Not sure what it climbs to when running.

I've talked with a mechanic and he's suggested I do a compression check cold, then another one warm. He asked me to bring him these results but didn't say why.

What would the cold/warm numbers tell him?"

gerald
05-05-2006, 08:25 PM
"I'm having a similar problem on my Merc 7.4L MPI. My oil pressure is reading 85-90, and a ten minute run at mid-throttle pushed close to a quart out the dipstick tube.

I pulled the PCV valve and it's not clogged. I checked the breather hoses from the opposite valve cover that connects to the intake plennum, and that's all clear too.

My next task is to do a compression check. Can anyone recommend a good reference manual for this engine? What should I see for compression pressure values on this engine?"

gerald
05-05-2006, 08:28 PM
My Merc is a 2001 w/ Bravo3 drive.

jimn
05-05-2006, 09:39 PM
"A cold compression test will show different readings from a hot test because all materials expand when their temperature increases. Water is one of, if not the only, material that expands as it gets colder and freezes. If there's a crack that reveals itself with higher operating temperature, it should show up in these tests.

Check the oil with the boat level and make sure there's not too much, make sure the PCV valve is clean and open (along with any other breathers), fresh oil and good fresh filter. If the oil that "is due to be changed" has more than 50 hours on it and the motor has been hard to start, it's likely that there's quite a bit of gas in it and that not only changes the viscosity, it also reduces the oil's ability to maintain a film on the moving surfaces. Long term loss of lubricity = worn rings and increased chance of scored cylinder walls and blowby."

sparky344
05-06-2006, 03:25 AM
I've since sold the boat. Let us know what you find out about your problem.