OMC 5.0 302 strange engine noise

vasy

Petty Officer 2nd Class
Joined
Dec 14, 2014
Messages
193
Last year was everything ok.
Oil is not milky or anything.... got any ideas what that extra sound is?
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
Sounds like a rod knock, if you rev it up slightly does it get louder?
 

vasy

Petty Officer 2nd Class
Joined
Dec 14, 2014
Messages
193
It follows with rom up/down. Not sure get too much louder as engine is also louder. Maybe by a bit.
I was wondering if this is more like top end problem with valves, or bottom end, as that is way more troublesome.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
The top end (lifters, valves, push rods) have more of a ticking sound, the rods have a knock and that's what I'm hearing. Remove the oil filter and cut it open to look for metal
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,056
Try removing 1 plug wire at a time and listen if the noise changes or disappears, that will usually locate the cylinder that is causing the knock. If the noise continues remove the valve covers and turn the engine over a little at a time and watch the rocker arms for full movement.
 

vasy

Petty Officer 2nd Class
Joined
Dec 14, 2014
Messages
193
I listened with a statoscope and isolated sound to Cylinder #1.
When removing the plug for that cylinder, the noise goes down but does not go away.
I guess not a good idea to run on 7 cylinders :)

Went to change oil, and it came out gray, looks like super tiny oil flakes in it.
I did not bother cutting oil filter open as I don't think it is needed due to the condition of the oil.
A little bit of a bummer, we finally have our 2nd warm weekend of the summer and it looks like the boat will have to be parked and instead of enjoying the water, will need to yank the engine out.

I'm debating it is it worth replacing the road bearings or just order a new block...….
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
If its not to bad a shape it could be rebuilt easy enough, but do need to inspect first.
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,056
At this point when you pull the engine flip it over and remove the pan. You may just need a reground crankshaft kit. If the main and rod bearings are not the problem the other cause may be a cracked piston skirt. Something I have encountered could be that I have seen is the crankshaft will break at the front counter weight, see if you can shake the harmonic balancer.
 
Top