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Need Advice Please

Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=50690
Printed Date: November-22-2024 at 7:55pm


Topic: Need Advice Please
Posted By: Tko87
Subject: Need Advice Please
Date Posted: June-19-2022 at 6:32pm
Mercruiser 454 Gen 4 on a FN noticed this summer on a few short runs I had to add some oil . Yesterday I traveled 90 miles, and when I got back to the landing oil pressure started dropped to drop below 10 psi...

Normal 70 cold
40-45 hot
65 running at 3k rpm’s

Anyway, I get home to find I have little or no oil and no leaks .. boat ran great .
Raw water temp 140-145 ( 140 Tstat )

Oil temp 220-228 (full temp )

Pulled the four easiest spark plugs on the corners and the starboard plugs had some dry soot almost like carbon .. plugs were brand new …. Hoping it’s either oil cooler but doubt it due to soot , so hopefully valve stem seals ?


Replies:
Posted By: MrMcD
Date Posted: June-20-2022 at 4:40am
You did not say how old this engine is but it does present like Valve Stem Seal failure, they can get old and crack.  One drop of oil per revolution can burn a quart every 400 miles in a car.  In your boat running at 3,000 RPM for 90 miles could do it.  
Depending on your tune a little detonation in a hard working boat could also fracture Piston Rings, the top ring fractures due to detonation pressure and things go south quick.  If a ring fractured you will have low compression in that cylinder.   Did the engine have increased blow by? 
If your OIl Pressure dropped that much it is getting very hot and breaking down.  Running low on oil in a hard working engine would do that.   The Oil sitting in the oil pan reservoir helps provide cooling for the oil.
If you were low on oil and sucking air at the oil pump the oil pressure gauge would be jumping up and down, a constant 10 PSI says your oil got very hot or the oil shortage started wearing out your Main and Rod Bearings opening the clearances.
Mark


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Posted By: KENO
Date Posted: June-20-2022 at 5:53am
According to this linked thread from last year it's a low hour used early 454 that he had some oil related questions about 

Maybe rebuilt at some time, Seal age..........who knows

http://www.correctcraftfan.com/forum/forum_posts.asp?TID=49679&PN=1&title=need-advice-please-keno" rel="nofollow - link

I think I'd fill it back up with oil and see how your oil pressure responds to see if you did some damage and do some looking at things like the oil cooler you mentioned and your crankcase ventilation system which can both sneakily use some oil on you.

Maybe temporarily bypass the cooler and pressure test it if the oil pressure is normal when you top it off with oil and run it.

Dry sooty plugs sounds like it's running rich on fuel mixture

Posted By: Tko87
Date Posted: June-20-2022 at 6:26am
About 400 hours on this engine …
Zero blow by

After filling with oil pressure was perfect

Note as soon as I saw oil pressure drop below 50 lbs I used the trolling motor .. I one notice drop to 10 when running it up. Trailer at an angle at the launch … zero noises from engine as well …there was still some oil in the engine . Not much though

Posted By: Tko87
Date Posted: June-20-2022 at 2:46pm
After pulling all the spark plugs all but 2 have excessive carbon buildup. Could this carbon build up get on the rings, causing oil to burn thinking of soaking them overnight with marvel mystery, oil, or something along those lines?

Posted By: MrMcD
Date Posted: June-20-2022 at 7:55pm
The classic tell for failed valve stem seals is a lot of smoke, blue smoke on a cold start.  The smoke clears up once the oil is burned off.   Piston rings would smoke and stay the same cold or hot.  Glad you did not hurt it.

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Posted By: KENO
Date Posted: June-21-2022 at 6:12am
Since it doesn't sound like you were leaving a huge mosquito killin' cloud of smoke in the exhaust and you used let's say, at least a gallon of oil in 90 miles, that oil cooler is looking more and more suspicious

Posted By: Tko87
Date Posted: June-21-2022 at 6:34am
Actually hard to tell with all the steam . However don’t smell oil … may run iron the hose this afternoon and check for smoke …

Posted By: Tko87
Date Posted: June-22-2022 at 7:54pm
Update

Ended up doing a top end engine clean to remove. All the carbon ended up doing it four times. Never seen so much carbon in my life. I had gotten this motor from a guy that lived in the Great Lakes. Had it rebuilt and only put a couple of hundred hours on it all up north with no thermostat.
Change my oil and filter a couple of times. Don’t see any blow by at all. No signs of oil in the water out of the exhaust only steam running on the hose, and definitely no water in the engine room... Oil pressure does seem a little high. I’m running straight 40. With cold engine and giving a slight rev to 2500 RPMs. All pressure will go up to about 90 pounds for a couple of seconds. Then immediately come back down to the 65 to 70 really starting to believe that I had excessive carbon buildup, making the piston ring stick and not be able to expand properly.

Posted By: KENO
Date Posted: June-23-2022 at 6:25am
Back in post #1 you said "boat ran great"

I don't think you'd be saying that if you had a huge amount of carbon deposits in your combustion chambers since your compression rings would be a mess too along with your intake valves

I guess you'll find out soon enough whether whatever you did cured your issues.

Posted By: MrMcD
Date Posted: June-23-2022 at 12:58pm
Steam only out the exhaust???   IS the boat on the water or sitting on the trailer?   In the water that may be normal, on the trailer that would be a problem with no water flow or not enough reaching the exhaust.   I have never seen a 454 carbon stick the piston rings, Honda engines yep, some Toyota engines but not one 454.

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