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Mystery rattle - Oceanranger

Posted: Tue Oct 04, 2016 12:55 pm
by JohnBrand
My Volvo 2003 runs well and without any obvious/unusual vibration. However, for some time there has been an annoying rattle which is just audible in the cockpit but quite loud in the aft cabin. Recently it seems to have got worse. It sounds like a loose board or similar, but it is prop-speed related: there's nothing until about 1200 revs, then is begins and continues to full throttle. The rattle has been impossible to trace inside the boat: it seems to be being transmitted through the hull. There is no obvious vibration on the propshaft.

I suspect either a loose shaft anode or the cutless bearing. Has anyone had experience of a similar noise? The boat will be on a drying grid shortly and I will investigate further.

If it turns out to be the cutless bearing, I guess it may be a lift-out job. Does anyone know if it is necessary to remove the propshaft, or can it be done by removing the propeller?

Many thanks,

John

Re: Mystery rattle - Oceanranger

Posted: Tue Oct 04, 2016 4:17 pm
by Wolfgang
What about opening the inspection hatch at the port side, sticking the head in and listening?
Once I had a loose nut of the engine mount. The nut danced at the end of the upper thread, on top of the mounting bolt.

Re: Mystery rattle - Oceanranger

Posted: Thu Oct 06, 2016 9:45 am
by Vegable
I frequently have a sort of tinkly/rattley noise towards the end of the season and find that there is no shaft anode anymore when the boat is lifted out. This year I've avoided plugging in to mains power (stray circulating currents) whenever possible and it hasn't occurred.....yet.
I lost a blade on my Brunston prop 3 years ago. The vibrations caused damage to the cutlas bearing so it was all replaced as an insurance job. The marine engineers had to remove the propshaft to get at the cutlass bearing, but I wasn't there to see how they did it.
Mike

Re: Mystery rattle - Oceanranger

Posted: Fri Oct 07, 2016 3:25 pm
by JohnBrand
Many thanks gents. Wolfgang, I've tried listening in as many places as possible without any positive results. Mike, I also found that my shaft anode had disappeared last year - I thought I had managed to super-tighten it this year, but we'll see!

I'll report the culprit when I manage to identify it.

John

Re: Mystery rattle - Oceanranger

Posted: Sat Oct 08, 2016 10:28 am
by Vegable
Reading your reply I've just had another thought, John.
When I used to race Minis, we used to use a broom handle to isolate noises in the engine. Stick your ear at the hands end, and the base on the engine part and you can very easily trace the source of the noise you're searching for.
Mike

Re: Mystery rattle - Oceanranger

Posted: Sun Oct 09, 2016 10:35 pm
by mikebuggy
This sounds like shaft anode...I've had it a few times. Be aware that it can travel up the shaft and abrade the hull at the shaft entry point.
Tip 1: You should ALWAYS place a jubilee clip on the shaft tightly up against both ends of each shaft anode (Ive got 2 anodes). Tip 2: You should ALWAYS totally fill the bolt holes, and the nut ends, on the anodes with silicon or sikaflex after you have tightened them fully. This prevents the surfaces around the fastenings eroding.

As for the Cutless bearing, you can change it with the shaft in place..I've done it. I either used a split pipe and a puller to drive the bearing out towards the prop end, or alternatively, I've also driven the old bearing forward onto the shaft, using the new one, or a slightly filed down (you want a loose fit) or thinner old one as a drift to drive it up the shaft out of the housing. Note that some P brackets have 2 grub screws and some have only 1. Once the old bearing is on the inner part of the shaft you hacksaw it carefully, on the diagonal, so you can split it off the shaft.

Re: Mystery rattle - Oceanranger

Posted: Wed Nov 02, 2016 12:32 pm
by Ocean Spirit
Have you got a Stripper rope cutter fitted?
If so, the 'fixed' cutter can rattle at low speeds. It is held in place by 2 little stainless 90 degree brackets but it does move slightly between the brackets, especially if they are worn. The movement of the fixed cutter, which obviously isn't totally fixed, can cause a rattle which disappears as the shaft revolutions increase.

Re: Mystery rattle - Oceanranger

Posted: Sun Nov 13, 2016 4:36 pm
by JohnBrand
Thanks for these helpful suggestions. AS Ocean Spirit suggested, the culprit turned out to be the 'Stripper' rope cutter - though the shaft anode had also disappeared. One of the two stainless steel brackets limiting the movement of the fixed cutter on the striker plate was bent sufficiently to allow the cutter to knock against the striker, and in my case it got worse as revs increased rather than disappearing. Unsurprisingly the local chandler had no replacement parts, but I have now bent it back and the rattle has disappeared. Ambassador Marine do a service kit for next time the cutter is accessible.

Annoying that the shaft anode had disappeared, for the second year in a row. Then new one is tightened as far as I dare, with plenty of sealant round the bolt heads and nuts. Fingers crossed!

John

Re: Mystery rattle - Oceanranger

Posted: Mon Nov 14, 2016 11:54 am
by steve parry
Hi John,

May I suggest using a loctite product instead of sealant, they produce various products for different jobs, one of them is purpose made for locking metal threads etc, comes in different colours for different strength's, It also comes in a small tube which lasts for a few seasons. Suggest you Google the product and have a look yourself to see what suits you. I use the blue for metal threads and touch wood none of my underwater fittings have come off(Stripper/anodes etc).

Regards

Steve

Re: Mystery rattle - Oceanranger

Posted: Sat Nov 26, 2016 11:42 am
by bhavers
Hi John,
Is the rattling sound similar to the sound i got at the end of this season?
See this post and the video in it: http://www.westerly-owners.co.uk/woafor ... f=2&t=3702

Kind regards,
Bram.

Re: Mystery rattle - Oceanranger

Posted: Tue Dec 06, 2016 6:52 pm
by JohnBrand
Hi Bram,

I see from your other post thread that it looks as if you've solved the problem - well done! You don't seem to have a rope cutter fitted, so that couldn't have been the culprit.

Best,

John