Knocking sound Mercruiser, help identify! /W Video

[krille_krille]

Engine/Drive started all of a sudden to rattle after wake boarding. When in gear and revs over 1500rpm the engine starts knocking, does not sound pleasant.... This is only in gear, when in neutral and rev there is no knocking sound. That should point towards the drive?
Please help me identify the problem with the help of the videos .

First video is at 2500rpm in gear. - Mercruiser 1 - YouTube

Second video is revving in gear from 1000-2500 - Mercruiser 2 - YouTube

third and last video is at idle, something is loose. - Mercruiser 3 - YouTube

What could the problem be? All help is appreciated.


Engine - Mercruiser 5.0 with Alpha one drive.

 

[Another retired guy]

Re: Knocking sound Mercruiser, help identify! /W Video

Hi. Listened to the videos but hard to tell which of the noises are normal and which are new. Unfortunately, you can't rule out the engine just because it doesn't knock when not in drive. Engine knocks are more likely to be heard when it's under load
Have you had any overheating, or oil pressure, problems recently?

 

[sti1471]

Re: Knocking sound Mercruiser, help identify! /W Video

sounds like noisy rockers under the valve cover.

remove the oil cap and put your ear up to the oil fill hole. If a rocker(s) are loose, you will hear it pretty loud inside the valve cover.

 

[krille_krille]

Re: Knocking sound Mercruiser, help identify! /W Video

Hi. Listened to the videos but hard to tell which of the noises are normal and which are new. Unfortunately, you can't rule out the engine just because it doesn't knock when not in drive. Engine knocks are more likely to be heard when it's under load
Have you had any overheating, or oil pressure, problems recently?

Thanks for the reply, no overheating. But the oil pressure, i can recall it was higher then 90degrees. What is standard oil pressure and what can high/low symptoms be?


thanks

 

[sti1471]

Re: Knocking sound Mercruiser, help identify! /W Video

normal oil pressure for this engine is 40-60. under load it should not be higher than 50.

 

[81 Checkmate]

Re: Knocking sound Mercruiser, help identify! /W Video

Oil pressure..
As Bondo would say .........10psi for every thousand RPM

Its measured in PSI not degrees.

It's hard to tell on video...but sounds like rocker/lifters to me.

If it's on the trailer...remove the drive and hook up water hose to the inlet on the thermostat and start it. To eliminate the drive as the culprit.

 

[Another retired guy]

Re: Knocking sound Mercruiser, help identify! /W Video

Thanks for the reply, no overheating. But the oil pressure, i can recall it was higher then 90degrees. What is standard oil pressure and what can high/low symptoms be?

90 psi??

thanks

90 psi ?? That's very high! Was that engine hot or cold? How many hours on the engine? Any engine work done recently?
High oil pressure is usually a good thing, but if it stays up there when the engine is hot it could indicate a problem with the oil pressure relief valve or a blockage somewhere. No idea if that's related to your problem very difficult to diagnose noises remotely.

 

[krille_krille]

Re: Knocking sound Mercruiser, help identify! /W Video

90 psi ?? That's very high! Was that engine hot or cold? How many hours on the engine? Any engine work done recently?
High oil pressure is usually a good thing, but if it stays up there when the engine is hot it could indicate a problem with the oil pressure relief valve or a blockage somewhere. No idea if that's related to your problem very difficult to diagnose noises remotely.

When i say 90 degrees i mean the pin on the gauge. 90 degrees = Straight up.


I have read and come across threads about ignition timing, that that can be the issue. Anything somebody can give an second comment on?

 

[81 Checkmate]

Re: Knocking sound Mercruiser, help identify! /W Video

Post a pic of your gauge...so we can tell what straight up means.

If you have that high of oil pressure....check the oil level on the dip stick.

 

[Another retired guy]

Re: Knocking sound Mercruiser, help identify! /W Video

I have read and come across threads about ignition timing, that that can be the issue. Anything somebody can give an second comment on?

Are you thinking it may be detonation / pre ignition ? Detonation is possible if engine was very hot and it has some carbon deposits building up. As it happened suddenly it's unlikely to be a timing issue - unless the timing chain jumped a tooth
As I said before, it's very difficult to diagnose a noise remotely. We're just guessing here. If you know a mechanic, have him/her listen to it.

 

[Bondo]

Re: Knocking sound Mercruiser, help identify! /W Video

Are you thinking it may be detonation / pre ignition ? Detonation is possible if engine was very hot and it has some carbon deposits building up. As it happened suddenly it's unlikely to be a timing issue - unless the timing chain jumped a tooth
As I said before, it's very difficult to diagnose a noise remotely. We're just guessing here. If you know a mechanic, have him/her listen to it.

Ayuh,.... I am,.... A lean condition will bring it on Fast, 'n ya never hear it, til it's tooo late,...

Pull the spark plugs, 'n do a compression test,... I believe that'll reveal the answer,...

Check the Contents of the fuel filter too,...