All a tremble at Calcutt

As I write, fitter Jim is wielding spanners in Herbie’s engine bay while virtual pound coins drop from my wallet into a bucket at a rate of one every 80 seconds.  Jim is doing his best to cure our engine shake, but up until now we don’t have a solution.  Let me begin at the beginning.
We reported at the wharf at 9 on Tuesday morning and after quite a while of engine running and listening and feeling around, Jim spotted that  the front engine brackets had a mounting tab broken off.  Here’s one:-

It’s twin on the other side was much the same and he securing bolts had shaken loose.  These days Calcutt have designed a modification to prevent this from happening.  This plate
 
fits across the end of the engine like this :

giving something stronger for the brackets to grip.
So that’s what we did.  The broken bracket were welded up,and  the new plate fitted. The engine was re-aligned to the prop shaft and we started her up.  Hmmm.  Our original vibration at about 1200 rpm had gone.  In fact there was a noticeable improvement higher up the revs too.
But, there was now a strong vibration at tickover or thereabouts.  We decided to ignore this for the time being and see how it affected us in cruising mode.  It could be that we could avoid these revs in practice.
Next day we ascended the Napton locks and it was becoming more and more apparent that the vibration was still a substantial problem.  What was more, the engine shaking was working various fuel pipes and unions loose and we were leaking diesel in a number of places.
So having ascended the Napton flight, we turned straight round at the top and came all the way down again. Grrrrr!
Returning to Calcutt this morning, we are back in Jim’s hands,and after consulting a colleague he is changing the four engine mounts as one of them did feel a bit soft.  It was felt we had to do this to eliminate it from the list of possibilities. Very soon now we will see if it has worked.  If it hasn’t, well, we had to replace the broken brackets anyway, and  I suppose  the new mounts won’t hurt.  Eleven years is not a bad life for such things.  So any money spent thus far has not been entirely wasted, but the prospect of the original problem of vibration not being solved is a real worry.
One thing that is good about Herbie’s design is that the front of the engine is accessible from inside the cabin, via a removable hatch under the steps.

This tends to make us remarkably popular with mechanics / fitters.

STOP PRESS
It didn’t work. :-(
Now we move on to the theory that it might be camshaft wear setting the engine running off balance.  This could get very expensive. An initial look at the rise and fall of the valves reveals that one of them might not be rising and falling enough but measurements have to be taken and checked.
Apart from all the potential expense and worry, our cruising plans are now all awry.
Watch this space.  I may post again later today as things develop.