385HP 454 Rod Knocking

[alldodge]

Boat is a 370 Regal with twin 385HP 454's and belongs to a friend. Engines had around 300 hours on them when the port engine had a rod knocking. Port engine (S/N 0L086675) was replaced with a new crate motor and everything is running fine again. My friend is real meticulous and is a bit OCD. Every year he goes and repaints the engine and gen because it doesn't look good. He runs royal purple oil and K&N oil filters.

Here it is 5 years later and the port engine has a rod knocking again. The port engine has about 250 hours on it. Now for the question, what could cause the same type engine to go bad the same way twice?

 

[Don S]

Re: 385HP 454 Rod Knocking

Take it apart if you can, and see what failed. May give a clue as to the cause of two engines, but doubtful.
Would have been nice if it was done to the previous engine as well so notes could be compared.
Could be two different problems and just pure bad luck and timing on that engine.

 

[Bondo]

Re: 385HP 454 Rod Knocking

Ayuh,.... Seein's we're just Guessin',...

I'm Guessin' it's from a lean condition induced Detonation,....

 

[alldodge]

Re: 385HP 454 Rod Knocking

Ayuh,.... Seein's we're just Guessin',...

I'm Guessin' it's from a lean condition induced Detonation,....

I heard another mention something to that effect. Thanks. This being an EFI engine what could we do to help reduce the possiability of it happening again?

 

[Bondo]

Re: 385HP 454 Rod Knocking

I heard another mention something to that effect. Thanks. This being an EFI engine what could we do to help reduce the possiability of it happening again?

Ayuh,... Clean clear fresh Gasoline is nice,...

I firmly believe ethanol is to blame, as this crap started, 'bout the time We started burnin' our food sources,....

Now-a-days, diligent care of the fuel filter is essential,...

 

[alldodge]

Re: 385HP 454 Rod Knocking

Thanks again, we both buy our fuel at the lake and marina's around here except one say they have no ethonol in the gas. Engines requires min 87 octane, and lowest octane on the lake is 90. He keeps is fuel tanks full all year long and replaces the filters ever year. My 502 EFI engine has the opposite issue, in runs rich. I have to pull my plugs every year to clean the carbon off of them. I took my boat to a dealer and they were of no help other than to help them selves to my cash. I keep my tank about 1/2 full and replace filters every other year, but I'm getting off topic. I know were still just guessing but I don't know of any way with an EFI to enrich or lean the injectors, do you?

 

[alldodge]

Re: 385HP 454 Rod Knocking

Some tmes you just have to go back to the basics and they have the answer. When the engine was replaced the mechanic put in the wrong plugs. They installed AC 41-803 instead of NGK BPR6FS or AC MR43T. From the pic (Port 41-803 and Starboard BPR6FS) we can easily see they 803 is a hotter plug and the gap even being erroded is currently .046

 

[aerobat]

Re: 385HP 454 Rod Knocking

how do you know for sure its a rod (bearing) knocking ? and how you knew for sure on the last engine ?

 

[alldodge]

Re: 385HP 454 Rod Knocking

how do you know for sure its a rod (bearing) knocking ? and how you knew for sure on the last engine ?

I wouldn't bet a high dollar amount but I would bet a couple cases of beer. Iv'e had 4 different times were I heard the sound I'm hearing now and all times it was a rod bearing. A broken skirt, cam bearing, rocker, bent valve do not make the same amount of noise which a rod bearing does (Double knock with each revolution). Will know more when the engine is taken apart.

I know the previous engine was a rod bearing because I talked to the guy who had it fixed the first time. This is not the same guy as the first (he bought it fromthe first) but is the same boat and motor which wa replaced.

 

[Bondo]

Re: 385HP 454 Rod Knocking

Some tmes you just have to go back to the basics and they have the answer. When the engine was replaced the mechanic put in the wrong plugs. They installed AC 41-803 instead of NGK BPR6FS or AC MR43T. From the pic (Port 41-803 and Starboard BPR6FS) we can easily see they 803 is a hotter plug and the gap even being erroded is currently .046

View attachment 200772

Ayuh,.... They're plenty dark enough,.... kinda blows my detonation theory outa the water,....

be interestin' to see the piston crown,...

'n No, I donno much 'bout the electronic motors, even with a couple in the fleet,...
I replace hard parts, 'n the marina's got the 'puter,...

 

[aerobat]

Re: 385HP 454 Rod Knocking

[Dodge;4273697]I wouldn't bet a high dollar amount but I would bet a couple cases of beer. [/QUOTE]

i,m asking because i,ve never saw anybody in our marina who had a connecting rod bearing failure on a GM block and also the forums keep quiet about such engine damages. whatever , with a bearing failure the rod normally des not knock every revolution but every other ( on a 4s troke) - exactly when this cylinder fires.

a knock every revolution would be heared more as a rattle and not a knock since even at 1000 rpm the crankshaft rotates 16 times a second.

i dealt with rod bearing failures in cars and there is an odd and risky method to check this out :

on a running and knocking engine pull a plug wire cylinder for cylinder . if at one cylinder with the wire off the knocking stops you indeed have a bearing failure on this cylinder , if the knock never stops even after testing all cylinders its NOT a rod bearing .

here i found a video with this procedure :

Connecting Rod Bearing Failure - 1997 Honda Civic - YouTube

should you get the idea to try this beware that you might get an electric shock - so i always did it only with a claws with good electrical protection and never by pure hand.

 

[brunolund]

Re: 385HP 454 Rod Knocking

[Dodge;4273697]I wouldn't bet a high dollar amount but I would bet a couple cases of beer.

i,m asking because i,ve never saw anybody in our marina who had a connecting rod bearing failure on a GM block and also the forums keep quiet about such engine damages. whatever , with a bearing failure the rod normally des not knock every revolution but every other ( on a 4s troke) - exactly when this cylinder fires.

a knock every revolution would be heared more as a rattle and not a knock since even at 1000 rpm the crankshaft rotates 16 times a second.

i dealt with rod bearing failures in cars and there is an odd and risky method to check this out :

on a running and knocking engine pull a plug wire cylinder for cylinder . if at one cylinder with the wire off the knocking stops you indeed have a bearing failure on this cylinder , if the knock never stops even after testing all cylinders its NOT a rod bearing .

here i found a video with this procedure :

Connecting Rod Bearing Failure - 1997 Honda Civic - YouTube

should you get the idea to try this beware that you might get an electric shock - so i always did it only with a claws with good electrical protection and never by pure hand.[/QUOTE]

the proper way to do this test is with plier designed for spark plug wires. they have a wire that you clip on to the engine.

better yet, loosen all wires first, use long needle nose pliers, with a wire grounding them out, and pull the wire of each plug. best is if you can ground out the wire when its off. don't leave it off for long while running

 

[alldodge]

Re: 385HP 454 Rod Knocking

Well lets put it this way, currently the engine is knocking loud. We shut it down and do not plan to restart because what ever damage there is we don't plan to make it any worste. When we get it apart I'll see what we find

 

[aerobat]

Re: 385HP 454 Rod Knocking

good luck and report !

 

[alldodge]

Re: 385HP 454 Rod Knocking

Got around to taking the motor apart today and found:

Engine has a Mrcruiser Repower plate on the side
Head and Rocker stud bolts have what appears to be white silicone on the ends.
Heads look good with no signs of preignition, only one cylinder shows slight sign of rich fuel mix
Piston tops all look good
Some of the push rods were installed up side down

Problem areas:
Oil pan splash guard shows copper bits all over it
All connecting rod bearings have no copper showing, all show scoring
Rod bearing number 7 was spun on to it self - pic1 both bearings on top of each other, Pic2 bearings separated
Did not remove main caps

The engine had 200 hours and had used Merc 25W40 synthetic blend and Merc filters.
The engine was a Merc repower so why did the bearings fail so soon? Assuming that since this was a Merc repower, or at least this is what we think it is, the engine was rebuilt correctly. The engine which replaced it is also a 2008 Merc repower, which was sitting in a Florida Dealer. Concerns now is what could have cause this to happen? Starting to think this engine should not have used the synthetic blend oil and maybe use what I use in my engines, non-synthetic straight 40W.



Ideas and guesses welcomed

 

[alldodge]

Re: 385HP 454 Rod Knocking

Bump - Any ideas

 

[Bondo]

Re: 385HP 454 Rod Knocking

Got around to taking the motor apart today and found:

Engine has a Mrcruiser Repower plate on the side
Head and Rocker stud bolts have what appears to be white silicone on the ends.
Heads look good with no signs of preignition, only one cylinder shows slight sign of rich fuel mix
Piston tops all look good
Some of the push rods were installed up side down

Problem areas:
Oil pan splash guard shows copper bits all over it
All connecting rod bearings have no copper showing, all show scoring
Rod bearing number 7 was spun on to it self - pic1 both bearings on top of each other, Pic2 bearings separated
Did not remove main caps

The engine had 200 hours and had used Merc 25W40 synthetic blend and Merc filters.
The engine was a Merc repower so why did the bearings fail so soon? Assuming that since this was a Merc repower, or at least this is what we think it is, the engine was rebuilt correctly. The engine which replaced it is also a 2008 Merc repower, which was sitting in a Florida Dealer. Concerns now is what could have cause this to happen? Starting to think this engine should not have used the synthetic blend oil and maybe use what I use in my engines, non-synthetic straight 40W.

View attachment 208470View attachment 208471

Ideas and guesses welcomed

Ayuh,.... I find it awfully hard to believe Syn-oil, vs. mineral oil caused any of that,...

Also hard to believe Mercruiser used silicone in the assembly of it,...

 

[alldodge]

Re: 385HP 454 Rod Knocking

I'm leaning your way, it looks like silicone but it is real white. The head gaskets used are silver looking and really stuck to head and block. Is there a way to find out from Merc reman number when and to whom it was sold. Wondering if someone took a tag off a reman and stuck it on this engine.

 

[Fun Times]

Re: 385HP 454 Rod Knocking

I'm Guessin' it's from a lean condition induced Detonation,....

I heard another mention something to that effect. Thanks. This being an EFI engine what could we do to help reduce the possiability of it happening again?

I believe (Not 100% sure) Mercruiser solved some of the problems with a lean condition going into cylinder number 7 by late 1998+. One problem they had with the 454/502 MPI's was the number 7 intake was not bored out enough to flow proper amount of fuel flow from the injector due to design. There are a few discussions about it on Offshoreonly that I see you're a forum member as well.

Do a search of "MPI #7 fuel rail defect???" and a few will pop up that you may want to at least know about.
Also this, 502 MPI - ASM lower intake versus stock
and there's one more good one over there about someone modifying the hole with photos, but for the life of me, I can not find it.:blue:

You said you had one cylinder that looked rich? Just curious which one? 6 or 8 by chance?

Is there a way to find out from Merc reman number when and to whom it was sold. Wondering if someone took a tag off a reman and stuck it on this engine.

From what I have noticed thus far, Some Merc remanufactured engines are not able to be identified by a Mercruiser dealer or online. The only way to have it identified would be by calling Mercruiser customer support in the U.S.

My 502 EFI engine has the opposite issue, in runs rich. I have to pull my plugs every year to clean the carbon off of them. but I don't know of any way with an EFI to enrich or lean the injectors, do you?

Start a new thread Just kidding. If all the engine sensors are working correctly and within range and the fuel PSI is normal and you have the correct spark plugs & your engine temp gets to 163 degrees, You should not be needing to do that for that reason.

You may want to do an injector balance test. You can find the procedure in the manual.

Also on Offshoreonly, search vst running rich.

 

[Volphin]

Re: 385HP 454 Rod Knocking

That crank needs to be checked out very carefully IMHO. Sometimes things just happen too. I've seen engines go with 20 hours on them. Usually traced back to incorrect assembly, or incorrect machine work.