What’s with the whine from the rear?

Canal Boat - - Back Cabin: -

QMy boat (with a twin-cylin­der wa­ter­cooled Lis­ter Al­pha en­gine and Cen­tre­flex cou­pling) pro­duces an un­pleas­ant high pitched whin­ing noise (ap­par­ently from the stern gland area) at medium revs in for­ward gear. I have dis­con­nected the cou­pling and the noise dis­ap­pears.

There does not seem to be a prob­lem with align­ment. Chang­ing the pack­ing makes some dif­fer­ence, par­tic­u­larly if it is not tight­ened much, but this is only tem­po­rary and causes leaks. There is no ev­i­dence of wear in the pro­pel­ler shaft. Is it pos­si­ble to re­place the bronze bear­ing with the boat in the wa­ter? ADRIAN MORTADA, via email

ATONY REPLIES: If it has a hospi­tal si­lencer and the en­gine is sound­proofed you could be hearing the pro­pel­ler’s hy­dro­phonic noise which is nor­mally drowned out by en­gine noise. It could also be a singing pro­pel­ler (Google ‘singing prop’and fol­low the in­struc­tions for grind­ing anti-singing edges), or even cav­i­ta­tion.

If the outer shaft was the cause, the noise should go for a while as soon as you use the greaser.

Odd though this sounds, make up a stout wooden plate and fit it in place of the weed hatch tem­po­rar­ily (make sure you se­cure it prop­erly). If the noise goes away, it is prob­a­bly vi­bra­tion caus­ing the lower part of the weed hatch as­sem­bly (the anti-cav­i­ta­tion plate) to rub on the trunk­ing. Either get the plate sup­ports strength­ened or use an an­gle grinder to trim the plate to give greater clear­ance.

I would not try to change any shaft bear­ings with the boat afloat.

De­spite what you say about the shaft be­ing cor­rectly aligned, I would check this care­fully be­fore do­ing much else

Noise may be com­ing from the anti-cav­i­ta­tion plate

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.