Merc 454 Alpha​ catastrophic failure - I have a few questions

B

bergs

Member
Aug 3, 2016
36
the humbling river
Boat Info
1987 268 Weekender
Engines
454 MPI w/ B3
Clearly there is no expectation of an internet diagnosis however I want to learn a few things about this engine since it mysteriously dumped oil in the bilge at some point and fried (what sounded to me like) a main bearing. I don't know if the oil was leaking which lead to the failure or if the failure occurred and the result was oil in the bilge.

I understand this is a GM-based block but are there any oil lines beyond what's used for the remote oil filter?

Are these engines known for any weak points? After all the research I did prior to buying the boat, I was left with the impression the 454 was robust. Did I miss something?

Before the failure, I was on plane and went WOT for maybe a minute. Tach was showing 4500 rpm. Was this a risky choice on my part? There were no indications of a problem before the stint at WOT and that was the longest amount of time I opened it up.

I am having trouble accepting that I blew this engine today but it kinda sounds like I did even though I don't know what I did wrong.

Please feel free to openly post your thoughts or questions. I would like to avoid this in the future.
 
Do you know the condition of the manifolds and elbows? Maybe you pulled in water and hydro locked the motor and cracked the block.


Sent from my iPhone using Tapatalk
 
If it is the original engine.....it is 30 years old. You didn't mention how many hours were on it but if it is original......a dozen of things could have gone wrong. More likely if you were at WOT when it blew..... low oil pressure caused it to fail under load. 454s have a great history but low oil pressure and water intrusion will kill them.
 
Where was the oil level when you first checked the motor prior to starting the motor?
 
it sounds you threw a rod and it punched the block resulting in the oil loss . very sad if that happened but after all the years it may happen . i,m also wondering a 454 is connected to an alpha drive ??? i never heard anything bigger than a 350 with an alpha and would assume the drive will not handle the torque pf a 454 for long
 
Manifolds and elbows were replaced the year before my purchase and the boat was run only a handful of times. Definitely did not hydrolock. There was a deterioration of something internal on my way back to the ramp.

According to the seller, the engine was rebuilt the year before putting it up for sale. I happen to think he bought a reman'ed block. I will be calling the marina that serviced the boat to see what records or info they can send to me. Exact hours on this engine are otherwise unknown.

Oil level was fine when I checked it in the driveway. Pressure gauge was showing just above 40 once it was warm and that to me seemed normal based off prior uses.
 
Any motor, new or old will blow if run out of oil. That Big Block is a stout motor if the rebuilder knows what he's doing. The remote oil filter are the only oil lines.

WOT for reasonable lengths of time are no problem for that engine. Depending on where the oil is coming from it sounds like someone did a substandard job rebuilding or assembling it
 
Is it possible for anything in the cooling circuit to fail in such a way as to allow small amounts of water to trickle into the engine? Not necessarily to result in hydrolock but enough to thin out the oil.
 
Everything is speculation till you tear into it. With a catastrophic failure it should be obvious what happened once it is apart. It doesn't sound like you did anything out of line, just bad luck.

Time to raid the piggybank.
 
Oil in the bilge..... Get that figured out first......Diluted oil is not going to make it into the bilge any faster than clean oil. How much oil was left in the motor ?
 
Things have gotten a bit more puzzling...

The dipstick is showing an oil level that appears to be 5x above the MAX line however it's not milky. I will have to take more time figuring this out and will post pics and more information once I get to the bottom of what's going on.

The bilge drained about 4qts of sludge.

Give me a few days to report back and, in the mean time, color me perplexed.

As a mechanical person, this is a first.
 
It will be milky when you drain it. This will cost several boat bucks, feelin your pain
 
I would confirm the type of oil pump installed. A high volume one with a standard 5 Qt pan is not good rebuilding. Sustained high rpm will pump the pan dry because the oil cannot drain back into the pan quickly enough
 
Sorry to hear of your troubles. There is however another oil line to check other than the remote filter. It's going to an oil cooler on the port side of the engine block. Follow your cooling hose for the engine and you should find a small in-line cooler with two oil line fittings. If this fails, it is more likely that oil will be forced out into the cooling water flow which would NOT cause an increase in your engine oil level - just the opposite. You would be leaving a trail of oil exiting out the exhaust.

My 268 was a 1989 so it had the 454/Bravo 1 setup. This was changed since many of the Alpha Drives were getting chewed by the 454 torque in previous models..
 
I have a 454 of the same vintage, with an Alpha One drive! 843 hours on it. I always go light on the throttle to try and keep the torque low on my ORIGINAL Alpha One. Sounds like water intrusion into block. Probably not from manifolds if they were replaced recently. I suspect an internal failure that let water in, maybe along the lines of a crack in the inlet manifold? Water sits at bottom of oil pan, if not fully mixed with the oil, so you may not see it as milky on the dip. Either way-it's gonna cost you some $! Break Out Another Thousand......sorry :(
 
Bt Doctur said:
I would confirm the type of oil pump installed. A high volume one with a standard 5 Qt pan is not good rebuilding. Sustained high rpm will pump the pan dry because the oil cannot drain back into the pan quickly enough
Click to expand...

Yep. I will never use a high volume pump in any motor. #1 it costs a few more horsepower to spin it but with a stock pan you can empty the pan. a high pressure pump is ok to use. i bought stock pumps and installed a small washer between the spring and cotter pin to increase pressure slightly. worked great on all of my 500+HP engines
 
I lost oil pressure in a car motor doing 120 klm/h - the hex oil pump drive had rounded through wear and spun in the oil pump resulting in loss of pressure.

Developed a knock within seconds. Motor didn't haemorage but the crank and rods were too badly galled to be reused in the rebuild.
 
might want to check to see if you blew out the front crankshaft seal.....I did that once in an old Jaguar I restored and lost most of the oil from the engine very quickly....

cliff
 
Who here would go with "water jacket failure"?

A friend brought up the possibility of this and I'd buy it as it would explain everything​...after WOT the jacket fails, the engine pulls water into the block, fries a bearing and eventually blows the seals due to overfilling of the block which dumps the excess into the bilge. I walk out the next day and measure high oil level on the dipstick from whatever oil remains in the block.
 
when you had water intrusion in the oil it would be milky IN ANY CASE . when you say its not milky it cannot be water in oil. whatever : oil level 5x above max will result the crankshaft punches in the oil mixing it up with airbubbles which is sucked by the oilpump. this results the oilpressure breaks down and you have an engine failure.
 
You must log in or register to reply here.

Forum statistics

Threads
113,100
Messages
1,425,928
Members
61,018
Latest member
IslandGirls1020
Back
Top