1992 4.3 Mercruiser knocking/clanging

[BOWTECH.JUSTICE]

I have a 1992 4.3 Mercruiser. Don't have the serial # right at the moment but I do know it begins with D8. Hope that helps. My problem is I took it out 2 weeks ago and started out fine but after a few minutes it developed a ticking, which sounded like a lifter, and once I loaded 3 more people and the motor got warmer, the ticking became more of a knock. I limped it back in and shut it down. After doing some looking I found the intake was leaking. I dug in, took lifters out and took them apart and cleaned them up. Everything looked pretty good in there. New intake gasket fixed the leak, changed spark plugs, changed oil & filter. Took it back out last night and the tick was tolerable but the longer it ran, it developed into a knocking. It's not necessarily rhythmic at higher RPM's, it's more of a rat-a-tat-tat. Also at WOT I'm only getting 3200 RPM's instead of the normal 4400. I keep thinking rod bearing (hoping that I'm wrong) but wouldn't that be more of a rhythmic knock?
By the way, this site is a great site for the not so experienced mechanics and DIYers like myself. Thanks ahead of time for any info anybody can help with.

 

[Bt Doctur]

rotating parts will usually be rhythmic ,intermittent could be detonation, poor fuel quality, phase separation of the ethanol fuel.

 

[BOWTECH.JUSTICE]

I need to take it and have it diagnosed, but I'm just trying to get some info before I do. Would those things cause it to be sort of a loud clanging?

 

[MikDee]

Check your crankshaft pulley/vibration damper to see if it's loose? I've heard them making odd noises, and not in a rhythmic pattern when loose..

 

[alldodge]

Suggest checking compression and timing

 

[BOWTECH.JUSTICE]

Thanks for the info guys. I figured out what the knock was after I started it today. Ran for a few minutes and once I had parts bust through the oil pan it made it easy to diagnose. Not what I hoped for.

 

[MikDee]

So sorry for your grief! I guess sometimes there ain't no justice!