It’s sud­denly got noisy

Canal Boat - - Back Cabin: Experts -

QMy 2007 Piper boat has a Beta 35 en­gine which is reg­u­larly ser­viced. I spend about three months a year tour­ing the canals and rivers and the en­gine has been very re­li­able. How­ever, it has now be­come very noisy when just tick­ing over and this is very ap­par­ent in locks. It ran as smooth as silk on the Trent and it wasn’t noisy, but once back on tick­over, the noise re­turns. Could this be due to ex­ces­sive vi­bra­tion? How do I check and re-align the en­gine mount­ings, or do they need re­plac­ing? MARTIN BRETT, via email

ATONY REPLIES… Does the noise come in or out of gear, or both. With a mis­aligned en­gine-shaft you would get the noise in gear but not out of gear; if it’s a bro­ken en­gine mount you would get the noise out of gear but less so in gear.

On tick­over out of gear, try push­ing the top of the en­gine to the left and then to the right. If the noise is re­duced it is pos­si­bly a bro­ken en­gine mount. Test­ing the mounts, un­less one is well and truly bro­ken, re­ally re­quires ex­pe­ri­ence. If a vis­ual in­spec­tion shows glossy black slime around a mount, oil or fuel has at­tacked the rub­ber so it needs a new mount.

You need to test each mount in­di­vid­u­ally. Get a length of strong metal, pos­si­bly a mooring stake, and lay it over the en­gine beds with the tip un­der an en­gine foot (on a Beta prob­a­bly a length of an­gle iron that runs the length of the en­gine), use this as a lever to try to lift the en­gine off each mount in turn. All should give by the same small amount be­cause of the rub­ber in the mount. Any that give more are likely to need re­plac­ing. Di­ag­nos­ing from lift re­quires ex­pe­ri­ence to recog­nise when it is ex­ces­sive. Be­ing rub­ber, the en­gine mounts will drop over time, but whether this causes en­gine-shaft mis­align­ment de­pends upon what type of stern gland and flex­i­ble shaft cou­pling you have. Aquadrive, Python­drive or long Centaflex cou­plings al­low lots of mis­align­ment so with those it is un­likely to be an is­sue. An­other Centaflex cou­pling al­lows a lit­tle. A Ve­tus stern gland and gear will also al­low the en­gine to drop a lit­tle with­out go­ing out of align­ment.

I sus­pect your en­gine is sus­pended part way up long studs in the top of the mounts. The top nut is usu­ally self-lock­ing, but the bot­tom ones can undo them­selves un­less checked for tight­ness at least once a year. If one of your lower nuts has come un­done it would give you this symp­tom so check all four lower nuts and tighten the lower nut back up to the top nut.

You can also get this sort of symp­tom if the nuts and bolts hold­ing the mounts onto the en­gine bed be­come loose so check all of those as well. How­ever, you might be best ad­vised to pay an en­gi­neer to test the mounts and check en­gine align­ment.

Fi­nally, the drive­plate could be fail­ing and an en­gi­neer should be able to iden­tify a fail­ing drive­plate within sec­onds.

The rear en­gine mount­ings

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