Clunk

[River's Revenge]

Recently I have heard a clunk in my 140 merc (GM) inline 4 cyl. it is there at idle but goes away when rpms are increased, I've hear this could be a wrist pin or possible a piston slap. I just has the entire rear end replaced so I am ruling out the gear case, Gimble bearing. Also by using a sounding stick it sound like it is coming from the front of the engine. I'd like some opinions as to my options. Right now I plan on running it until it fails. could be a week or a year. not sure. I haven't had it loaded yet but I am hoping that once it heats up and expands it might be ok, Kinda like an old oldsmobile. ha! Also the front frost plug has pushed out but seems to be intact and holding (1/4 inch of the edge is showing).

Please, any thoughts on what could happen. I know the worst case scenario..

 

[grahamh]

Re: Clunk

If it's coming from the front of the motor, and it increases with motor rpm (up to a point) than my guess is it's a rod knock, but I'm really just guessing.

If you plan on rebuilding the engine, don't run it until it fails--if a rod fails, the piston/rod pieces can and will punch holes in the block, rendering it irreparable.

 

[River's Revenge]

Re: Clunk

here's some food for thought. This clunk dissapeared when I applied pressure to the aft cowling around the coupler. Then I found an aluminum washer spacer in the bilge. (The motor had been removed and reinstalled recently.) so as i looked at the exploded view this spacer is a cap type washer/spacer for the rear mount. Seems to me a possible reason,,, if one side has it installed and the other is in the bilge well, this would cause mis-alignment and could be my clunck at idle.

I hope to check to see if there is one installed on each side.

Boating season is here and I'm not up and running yet...uhgg!

 

[boat127]

Re: Clunk

i would check the rear engine mounts to see it all the hard ware is there and installed correctly the knock could be from that washer not bein installed on the bolt. if you look back there look at the rear mounting bolts and see if that washer is on both bolts then look to see if the spacers can move up and down freely they shouldnt

 

[River's Revenge]

Re: Clunk

Thanks boat 127, I hate second guessing myself. seems right, if both are not there this should be my problem. If I shore up the belly of the engine and slowly lift the engine ever so slightly, by doing this in steps i should be able to slide that washer back in without messing with alignment too much. Heck if the clunk gets worse i'll just have to do the alignment over. Easy miss on the mechanics part but shouldn't have been overlooked when re-assembled,

enjoy!

 

[wca_tim]

Re: Clunk

sorry man, but if you move anything with the engine mount you NEED to realign the drive / engine.

note that your noise could also be a ujoint if it's coming from the back... I would say that unless you take it apart and check everything, you
've got a [pretty reasonable chance of paddling in your future... or maybe even sinking (u-joint goes out bad under power, shreds the bellows, you have a softball size hole in the engine compartment that would be very difficult to plug up..)
..

just some food for thought..,.

 

[River's Revenge]

Re: Clunk

I like the food for thought. I'm a 1 plus 1 = 3 kinda guy. Ya never know what ideas can make ya think. The u-joints are both new. And i totally agree with if you mess with any motor mounts ya should re-align. heck I've heard many people wrestle with the alignment 4 may 5 times or better just to get is right. We'll see.. one of these days I'll win the lottery and be able to throw more money into that hole in the lake.

by the way this is a 78 carlson cvx16ss. and shes finally comin together.

good boating days are near.