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Clonking Noise ?

Androo

By Androo
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Androo Proficient

Androo

Posted
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Is this normal ?

 

When I have the throttle lever in neutral and engage forward or reverse there is an annoying clonking noise. I always allow a few

 

seconds before going from Forward/Rev or Rev/Forward and I move the lever gently to it's position

 

Does something need adjusting to stop this like a cable etc...?

 

The engine mounts are new and tight but, even with the old engine mounts it still did this.

 

BMC 1500

 

PRM Gearbox

 

Is this a common BMC/PRM problem?

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Androo Proficient

Androo

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Have you checked the gearbox oil? and can you pull the prop shaft back and forward by hand?

Gearbox oil was changed last Sept 20hrs done since then.

 

Regards prop shaft, not done that. What does that mean anyway?

Or could be the drive plate (between engine and gearbox) on the way out.

 

I should have asked is this a new thing or has it always done it?

Since I bought the boat 5 years ago it's always done this.

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saltysplash Experienced

saltysplash

Posted
Posted

Gearbox oil was changed last Sept 20hrs done since then.

 

Regards prop shaft, not done that. What does that mean anyway?

Since I bought the boat 5 years ago it's always done this.

If the shaft is loose it can shift forwards and backwards when engaging gears.

I had one try to exit the boat once when emergency reverse was engaged

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Geoff Taylor Collaborator

Geoff Taylor

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Hi, Just a thought, if your engine idle RPM is a little too high it can amplify the engagement noise of the gearbox, PRM gearboxes are designed to permit changes from forward to reverse at full revs without damage so I would be looking towards a drive plate check. (BMC 1500 idle approx 600 RPM).

 

Our boat has a PRM 150 connected to a Perkins 4108 and is literally silent when forward or reverse is engaged regardless of revs.

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Androo Proficient

Androo

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PRM mechanical or hydraulic gearbox? I think a PRM mechanical one may well do that, especially if the revs were a bit high but it definitely worth checking the drive plate.

Mechanical. I always let the revs die down before changing. Idle is set at approx 650rpm

Does it have an aquadrive/python fitted? Mine was rattling like a good one and turned out to be a loose bolt.

I have a flexible coupling and all the bolts are tight.

Mechanical. I always let the revs die down before changing. Idle is set at approx 650rpm

I have a flexible coupling and all the bolts are tight.

Does checking the drive plate mean, splitting the gearbox/engine? or is there an inspection hole?

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pete.i Rising Star

pete.i

Posted
Posted

Hi

The drive plate is attached to the face of the fly wheel. In the same place that the clutch would be attached in a road vehicle. It does a similar job to a clutch in as much that it takes up some of the initial torque when you engage forward or reverse on your boat. because of where it is attached the only way that I know of to inspect it is to separate the gearbox from the engine. I have a BMC 1.5 and Hurth gearbox and I do not have an inspection hole. An "on the way out" drive plate can cause clunking but as Richard (RLWP) says some gearboxes clunk anyway, mine does.

 

Pete

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  • 1 month later...
Traveller Rising Star

Traveller

Posted
Posted

Revising an old topic. My gearbox does the same (more apparent when the engine/gearbox is warm). It only happened at low revs (when passing moored boats on tick-over for instance) and goes away once the revs are increased. It is not noticeable in reverse.

What oil is recommended for a hydraulic box?

 

Tks

Colin

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Grace and Favour Veteran II

Grace and Favour

Posted
Posted

Revising an old topic. My gearbox does the same (more apparent when the engine/gearbox is warm). It only happened at low revs (when passing moored boats on tick-over for instance) and goes away once the revs are increased. It is not noticeable in reverse.

 

What oil is recommended for a hydraulic box?

 

Tks

Colin

You'll need to tell folks which gearbox you have - - different boxes use quite different lubricants

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Tony Brooks Veteran II

Tony BrooksDonate to Canal World

Posted
Posted

If it is oval in cross section with a vertical longitudinal split and fins cast on the outside its is probably a Hurth (Automatic transmission fluid).

 

If it is sort of oval or heart shaped and looks as if it has been fitted by a drunk (because it looks skewed on the engine and it has a couple of hydraulic hoses comping out of it then it is probably a PRM hydraulic (engine oil).

 

Once you eliminate those two we need a photo. At that age it could be a TMP hydraulic or a number of other makes.

 

Unless it has been changed in the last few years it is unlikely to be a PRM mechanical box. These are rectangular with rounded corners in cross section with no vertical split. They have fins cast onto the case. They now use Automatic transmission fluid.

 

Do not extrapolate from this post to an unknown box. post a photo.

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Traveller Rising Star

Traveller

Posted
Posted

Thanks for this Tony, I am away from the boat for a few days now but will have a look-see again when I get back. The PRM looks likely but I can't remember it looking as though a drunk had fitted it :-). What I do remember is the filler cap is a large hexagonal job with the dip stick going through the middle of it.

A picture will follow idc.

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Traveller Rising Star

Traveller

Posted
Posted

My gearbox does the same (more apparent when the engine/gearbox is warm). It only happened at low revs (when passing moored boats on tick-over for instance) and goes away once the revs are increased. It is not noticeable in reverse.

 

 

Thanks Richard, so engine oil it is? Any thoughts on the noise?

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RLWP Veteran II

RLWP

Posted
Posted

Thanks Richard, so engine oil it is? Any thoughts on the noise?

 

Engine oil it is

 

The clonk - ours does it too and has for years. I suspect if I took it apart I would find the splines on the forward clutch to be worn. As long as it still works, I'm leaving it alone

 

Richard

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Traveller Rising Star

Traveller

Posted
Posted

 

It's definitely a PRM of some kind then

 

Richard

Just been trawling pics on Google and it could well be a TMP gearbox I think. A TMP certainly has the same oil filter arrangement and also sports a hexagonal filler nut through which the dip stick passes.

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