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Prop creep


mazer

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Hi I have a lister sr2 coupled with an LH150 hydraulic reversing gearbox. While checking the engine I noticed that the prop shaft did a complete revolution on starting up (in neutral) then started to creep very slowly. I have checked the oil levels in the gearbox and clutch and they're both normal. Is this normal or do I have a problem?

Thanks in advance for any help you can give me.

Mazer

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It sounds like your box is a little slow at building oil pressure. When stopping your engine after a run and the boxes oil pressure drops it automatically goes into forward gear. When starting your engine the prop shaft will revolve a little in forward until the oil pressure has built up which should only take a couple of seconds and stop. It should not really slowly turn in neutral after a few seconds. I'd say your oil pressure is slightly on the low side. This can be adjusted with the use of a pressure gauge and by altering the shimming at the control valve. However a good flush out and oil change works wonders with these boxes and will probably fix it. There is fore and reverse adjustments in these boxes but wouldn't be causing that, although they are well worth checking.

 

ETA. It is also possible that your g/boxes control cable is out of adjustment meaning that the actuating control valve lever on the boxes side where the cable attaches is held slightly forwards causing slight pressure loss even though your Morse control lever is vertical ''in neutral''. Adjust cable so that when the Morse control is in neutral the boxes control valve lever is also vertical and in neutral.

Edited by bizzard
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Just to add to Bizzard's reply, the LH150 box is designed to go into forward if anything goes wrong. So if the pump failed, or all the oil leaked out, it will go into forward. I suspect you box is just taking a little time to build up pressure, like Bizzard said.

 

I wouldn't do anything to it if it works OK otherwise

 

Of course, if you did want the pump checked and the control valve shimmed and reset, I'm just finishing off a test rig to do those very jobs

 

Richard

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Thanks Bizzard. There seems to be some play in the morse control but even when the gearbox control is vertical there is still creep. So I'll flush out and refill the box hopefully that will cure it.

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Thanks Bizzard. There seems to be some play in the morse control but even when the gearbox control is vertical there is still creep. So I'll flush out and refill the box hopefully that will cure it.

I'd just mix 50/50 a pint of either paraffin or diesel fuel with a pint of engine oil to flush, and run gently in gear for about 15mins changing from fore to astern occasionally, drain off by leaving plug out for a few hours then. replace plug and refill with 2.1/2 pts approx of Hypoy SAE 80/90 gear oil.

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