Mercruiser 5.0l knocking sound?

[Dutchlarson]

I recently purchased a boat with a 5.0l mercruiser engine.

It runs ok i think, starts ok cold as wel as warm. Temperature and oil pressure ok.

However i think i'm hearing a knocking sound coming from the engine.

Any opinions? https://youtu.be/dn1pebL7KCY

I know its not that loud but if there is something wrong i would like to fix it on time.

Or maybe the experts here say it sounds just fine?

Thanks in advance for the advice!

 

[alldodge]

Unless it gets louder I would just keep listening. That said I hope you have listened closely to the vid to know what where hearing is what it sounds like.

It might just be exhaust flappers

 

[Dutchlarson]

That said I hope you have listened closely to the vid to know what where hearing is what it sounds like.

Not sure what you mean by that? The video i made myself, that is my engine.

Hoe do i check the exhaust flappers? I tried listering with a wooden broom stick on several places but i hear nothing special.

Or does anyone thinks it just sounds ok?

 

[alldodge]

The sounds can be different from what you hear and what is actually heard over the net on Youtube. I say this because I don't hear much to give me concern but you may have heard something a little different. Just info to think about, nothing more

The exhaust flappers are below the exhaust elbows. You didn't mention what year (or serial number) your motor is so we have a bit of trouble trying to identify which parts. Its always best to let us know exactly what your working on. Here is the flappers on a 88 to 95 model item 6

http://www.mercruiserparts.com/bam/subassembly/31835/1014/370

 

[Dutchlarson]

Ok thanks for the help and explanation.

Maybe im a bit over concerned because i had mich trouble with my previous boat.

This is a '04 Mariah SX22 with tje factory original engine. It ran about 350 hours and is well maintained.

 

[alldodge]

Since this is a new to you boat its always best to start with a clean baseline. This way you know what you have and when it was done. If you haven't done it already

Change the oil and filters
Remove the drive ad check engine alignment, paying close attention to the drive coupler. Make sure teeth and nice and squared shape
Drain and replace the drive lube, clean out and refill lube bottle
Check gimbal bearing for smoothness and also U joints
Change impeller
Change fuel filters

While doing this you may find your issue

 

[QBhoy]

Hard to tell from video....as AD says...could likely just be the flappers. Have a listen towards the back of each side of engine where the exhaust manifolds go into the cow horns.