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mikeani
mikeani

Posted: Wed Dec 09, 2009 12:28pm

Post Subject: bmc 1.5 diesel prm gearbox

When engaging drive at tick over the gearbox makes a clattering noise which disappears as you accelerate. Oil level in gearbox is at maximum and not losing any oil. What is it likely to be do you know and could it be serious?

Tony-B
Tony-B

Posted: Wed Dec 09, 2009 9:17pm

Post Subject: bmc 1.5 diesel prm gearbox

Michael, It would be a little help if I knew which PRM box you have because one of the more common hydraulic ones seems to suffer from chatter between the teeth when on tick-over. This is caused by the fact that engines tend to speed up and slow down their crankshaft twice in every revolution. However I do not think I would normally describe this as clattering. I strongly suspect the drive plate between the engine and gearbox is on the point of failing and suggest you get it looked at ASAP because if it totally fails you will have no drive. If the plate looks OK I suggest that you contact PRM and ask that they recommend a drive plate that will minimise tooth chatter. Tony Brooks

alanclarke
alanclarke

Posted: Wed Dec 16, 2009 10:37pm

Post Subject: bmc 1.5 diesel prm gearbox

i had the same problem myself on my prm gearbox/1.5 bmc engine, it clunked horribly when engaging either forward or reverse and rattled like hell when travelling although the more the gear box was put under pressure i.e the faster we went the rattle quietened a little, i had a new drive plate fitted and problem solved, cheers, alan

mikeani
mikeani

Posted: Wed Dec 23, 2009 12:08pm

Post Subject: bmc 1.5 diesel prm gearbox

Thank you for your explanation. Is it feasible for me to replace the drive plate myself? I am a qualified fitter and turner admitedly not on narrowboat engines, only nuclear submarines!!

Tony-B
Tony-B

Posted: Wed Dec 23, 2009 1:30pm

Post Subject: bmc 1.5 diesel prm gearbox

Dear Michael, the job itself is fairly straightforward - in theory, but there are some things that can cause problems. I will run through the steps with some comments. 1. make sure there is some give in the cooling hoses and fuel pipes that will, if required, allow you to lift the back of the engine. 2. Remove one set of bolts from the propshaft coupling, turn the rudder to "full lock" and twist/push the propshaft backwards until it will go no further. You may have to slacken & re-tighten the stern gland to allow this. 3. remove the control cable from the gearbox and if its a hydraulic box disconnect the oil cooler. I would disconnect the water (more antifreeze needed when refilling) but as long as you observe cleanliness you could disconnect the oil pipes and cap them so no dirt can get into either the pipe or cooler. 4. The gearbox is normally fixed to an adaptor plate which is a large round plate attached to the flywheel housing by a ring of bolts. Undo the bolts (and possibly struggle with the lower ones!). 5. Draw the gearbox backwards and hope it comes free of the drive splines before it hist the shaft. If it does hit the shaft undo the rear mounts and jack the back of the engine up so the box clears the coupling. If you do this please take great care over realigning the shaft. 6. You should now see the plate attached to the flywheel with perhaps 6 or 8 setscrews. Undo the screws to remove the plate. Beware the box may be heavy and difficult to handle. Tony Brooks

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