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Big end wear or damage

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Please excuse my terminology and somewhat blunt approach to asking for help but here goes.

I've a 16/2 in my canal boat that was marinised for the boat and it had run very sweet for the last 10 years ( about 2000 hours on it) Recently cruising along the canal I noted smoke coming from the crankcase breather and a distinct 'knock' - never heard before. On advice from the people who put the engine in the boat i got access to the engine via the crankcase 'door' and under one cylinder these were pieces of metal, small  - on showing this to the installer they suggested it was the big end shell bearing.

On that side I can introduce same 'knock' by grabbing the bottom of the conrod and feeling some movement which i assume means the big end 'shell bearing' has failed. i suspect the smoke was the bearing heating up during its failure. I may be to blame for this as I had not completely filled the engine to the top mark on the dipstck   -I assume therefore the bearing has run dry and hot hence the smoke and bearing failure ?

The same engineer suggested unbolting the conrod and checking for wear/damage with a view to replacing the bearing. Now I have seen there are different thicknesses of replacement bearings shells to ( I assume) account for wear such as I may have. He suggested this should be an easy thing to do and check... he's experienced I am not

My questions to the enlightened is ..... is is a relatively simple thing to unbolt the conrod via the open side of the crankcase. Then is it a matter of checking the surface as well as measurements of the shaft the conrod bearing clamps to. If there is not real wear replace the shell bearing with like for like .... if there is wear replacing the shell bearing with one to compensate for the wear?

Obviously if the crankshaft surface is damaged too badly i expect that it is the crankshaft out to have it build up and turned back to spec?

Sorry if my questions are basic and contain incorrect assumptions and or terminology. I'm struggling to get anyone to take the work on and I may have to get my own spanners out .... hence the questions ?

Any observations/experience or feedback gratefully received


Hello Nev,

Simple, yes.  Easy?  Meh.  Not easy.  But not hard either.  Firstly, my engines have had a bit of a "spacer" located between the connecting rod and the cap.  This spacer (or series of spacers) sets the clearance between the "big end" and the shaft. 

I did the math with the engine disassembled.  IF I recall correctly, you're wanting 0.0015" inch of clearance for every inch of diameter of your shaft.  My 30/2 was set up with ~ 0.004" of clearance on both connecting rods.

Now, the next part:  Being that your engine is still together, you're going to want a different way to measure your clearance.  You need to go to a "good" auto parts store and get yourself a hold of some "Plasti-gauge".  You're looking for some that's accurate in the 0.002"-0.010" range.  Follow the directions, and check out your current clearance.  Adjust as necessary.  PM me if you need more assistance.

Hi, Thanks for taking the time to respond to my question - I've sent a PM



Adding to the other reply if you did indeed melt the bearing it is imperative that you clean the crankcase. Personally I would also pull the oil pump and check it for debris  and flush the lines. The Lister technical data specs the  clearances with new parts at .0025"- .003" with allowable wear .003". So, clearance could be as large as .006" and be within the spec to run it,  however I would never let one out of the shop with that much clearance.


OP, is that a genuine Lister CS 16/2 engine you have in your canal boat?

Or is something more like this (and of Indian origin)?


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