Bukh DV20 mid range graunchiness

[wightacorn]

Our DV20 has developed a nasty graunchiness in mid range (2000 rpm-ish) This is not present at low revs nor at high revs and, otherwise, the engine sounds fine. The noise is there whether we are in gear or in neutral and seems to come from the rear of the engine. Initial thoughts from Bukh UK were that it was most likely worn engine mounts. Engine mounts have been replaced to no effect - has anyone any ideas what might be causing this noise?

 

[neil_s]

You might have a crack developing in the exhaust injection bend.

Neil

 

[SimonJ]

Apart from exhaust bend there is not much at the back of the engine. I find it diffcult to pin down the exact location of noises from my BUKH but have learnt what can fail! I sometimes also get sympathetic (?) resonance of pots/pans in nearby lockers.
Only other suggestion is to report a recent noise I had which turned out to come from the waterpump/hand start drive. The solution was to replace the bearings - fiddly, but not too difficult. Replacement bearings came from BUKH but could easily be obtained from a bearing supplier such as Brammer (likewise waterpump seals). You know doubt know that water pump seals do fail and can allow water to get into the above bearings (at the least) and the sump with more devastating effect (at the worst) . A long handled screw driver used as a stethoscope may help you locate your noise (end on the engine/ear to the handle).
Good luck!

 

[rhumlady]

Water pump seals from usual sources (bsl Brammer etc) have springs which rust! Well worth the small extra cost from Bukh etc.
If you are looking at the Exhaust bend then you are best taking it off. I nearly missed a crack in mine when I checked it while on the engine.