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tonyblay
tonyblay

Posted: Sun Sep 13, 2009 7:50pm

Post Subject: Lister gearbox

My boat has been restored after sinking, I am having trouble with it sticking in forward gear, I have changed the oil 4 times, it does eventually kick out of gear several hours after stopping the engine it kicks out on starting. Any ideas to resolve problem would be most welcome. Engine SR 3 cylinder, LH 150 gearbox.

Tony-B
Tony-B

Posted: Mon Sep 14, 2009 7:31am

Post Subject: Lister gearbox

Dear Anthony, your question makes no sense to me - are you sure you know how the gearbox is supposed to work. The LH150 is a hydraulic gearbox and in common with all hydraulic gearboxes a way should be engineered into the box to ensure that loss of oil pressure does not result in a total loss of drive. The PRM box has a special mechanism you can activate but your box (the LH150) has a far more elegant solution in that it uses hydraulic pressure to select reverse and neutral but with no pressure in the box (as in its run out of oil or the engine is not running) the box goes into AHEAD and stays there until internal oil pressure is restored. This means all the time the engine is stopped a double set of springs are forcing the box into gear. If you watch the prop shaft on a correctly working LH150 as you start the engine you will see the shaft turn for a moment as the engine starts. This is correct and normal. Seeing its mechanical spring pressure combined with a lack of oil pressure on a piston that engages ahead gear I can not see how it can "kick out of gear several hours after stopping the engine". If the sinking had blocked the oil passage leading to the ahead position to such an extent it took hours to allow the ahead clutch to "kick in" (select ahead gear) it is almost certain that selecting astern soon after starting would engage both ahead and astern and thus lock the box solid. Sorry, I simply do not understand the question. When the ahead cone clutch wears they do occasionally jamb in ahead so selecting astern locks the box solid, but that is not what you say happens. There are also two critical adjustments required inside the box. These are detailed in the back of the SL/SR manual that can be downloaded from a Dutch website. You will find a link at the bottom of my first webpage (www.tb-training.co.uk). Please come back with a fuller description of what you mean if this does not give you the answer. Tony Brooks

tonyblay
tonyblay

Posted: Mon Sep 14, 2009 1:51pm

Post Subject: Lister gearbox

Hi Tony, The problem I have is the gearbox sticks in forward gear, it will not come out of gear when put into neutral. This has only happened since water contamination into the gearbox. I have changed the oil several times as I thought this might be the problem as after running for 30 minutes or so the oil looks "creamy". I can't get at the drain plug so I am pumping the oil out of the dipstick. Do you think I will have to remove the drain plug to completely get rid of the water and is there a method of flushing the system without damaging the gearbox? I have the manual and note the settings you have mentioned which I will check, however as this problem has only occured since the water contamination I think it is the likely cause for the hydraulics not working. I am not an engineer, but I am not afraid of having a go and getting my hands dirty, any help you have to offer is greatly received. Tony

Tony-B
Tony-B

Posted: Mon Sep 14, 2009 2:16pm

Post Subject: Lister gearbox

When those gearboxes stick in ahead and refuse to engage neutral the usual reason is the ahead cone clutch has stuck in place. This is usually caused by wear in the female cone (possibly where lining rivets have ground into the metal cone depending upon age) but it could also be rust between the surfaces. I would normally expected rust to be worn away after a few changes from ahead to astern but if the ahead clutch is jambing then that may cause further damage as the box locks in two gears at once. If the oil is now only streaked with cream or only faintly creamy then I doubt oil has anything much to do with it. I know of no easy way to flush the box. I suppose you are using gear oil in the box - I think it requires SAE 80 gear oil - not engine oil. Take the lid off the box as per the manual and use a bolt from the top to jack the ahead piston forward (its all shown in the manual)while you watch the linkage and cone. It should gradually withdraw the cone until you can turn the shaft coupling by hand. If the bolt gets stiffer and then the cone releases with a snatch then its a problem with the cone clutch. Your contact for all things marine Lister is Marine Engine Services at Uxbridge. Tony Brooks

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