Thornycroft Mitsubishi Engine stuck in reverse

[Traveller21]

Hi,

I wonder if anyone can help with this. My son's 1986 Les Allen 48ft boat snagged a fly tipped tent into its prop/screw the other day which being nylon managed to stall the engine. The tent was fully removed and the engine started as usual on the first touch but is now stuck in reverse? We've tried the gear lever and it looks like it's pulling the right levers? Any ideas on how we might get it out of reverse would be very welcome.

Best wishes to all for the new year.

Matthew 

Edited January 4 by Traveller21
Added photos

[Tony Brooks]

I think that we need the make and model of gearbox or a decent photo of it.

[Tracy D'arth]

Its not the engine that is in reverse but the gearbox.

 What is the gearbox?  

Did you have to get in the stern and remove the weed hatch to free the prop?  Has a foot been plonked on a cable or linkage?

 

 You say "levers", how many?  Can we have a picture of the gear lever/s please?

Edited January 4 by Tracy D'arth

[Traveller21]

Hi Tony,

Many thanks for your initial thoughts. I'm not with the boat right now but son can't see the make of gearbox but has sent me these photos. Hopefully they might be helpful

 

Cheers,

Matthew 

[Tracy D'arth]

6 minutes ago, Traveller21 said:

Hi Tony,

Many thanks for your initial thoughts. I'm not with the boat right now but son can't see the make of gearbox but has sent me these photos. Hopefully they might be helpful

 

Cheers,

Matthew 

No photos posted.

[David Mack]

Just now, Tracy D'arth said:

No photos posted.

They are in the first post.

 

Looks like PRM gearbox but we can't see the actuating lever and connections.

[Traveller21]

Should be photos now? 

[Tracy D'arth]

Looks to be a PRM 160 box. Single lever on the port side.   Do you mean it only selects reverse or it is in reverse no matter where the lever is placed?

Check the oil level on the gearbox dipstick under the brass plug on the starboard top of the box, unscrews and the dipstick it attached.

The gear lever should detent the lever on the box forward and backward of neutral.

If it does not, disconnect the cable from the gearbox end and manually move the lever on the box. If it then works forward - neutral - reverse then it is the cable or linkage that is causing the problem.

I am suspecting a big foot problem.

5 minutes ago, Tracy D'arth said:

Looks to be a PRM 160 box. Single lever on the port side.   Do you mean it only selects reverse or it is in reverse no matter where the lever is placed?

Check the oil level on the gearbox dipstick under the brass plug on the starboard top of the box, unscrews and the dipstick it attached.

The gear lever should detent the lever on the box forward and backward of neutral.

If it does not, disconnect the cable from the gearbox end and manually move the lever on the box. If it then works forward - neutral - reverse then it is the cable or linkage that is causing the problem.

I am suspecting a big foot problem.

If the box is in reverse all the time and you cannot get it into neutral i.e. out of gear, then the cable has snapped/come undone/linkage fallen off.  That box is utterly reliable. The problem will be outside the box, linkage or control or cable.

Edited January 4 by Tracy D'arth

[Traveller21]

Hi Tony,

Many thanks once again for your brilliant advice - I'll copy and paste your reply to my son and either he'll have a go or I'll try and get down to him this weekend.

Best wishes,

Matthew 

[Tony Brooks]

I think you meant to thank Tracy. I agree with all she said,  especially disconnecting the cable from the gearbox lever and moving that lever by hand.

 

I would add that it looks as if the end fitting on the gear cable may have fallen off the cable.

 

Those PRM Hydraulic boxes are pretty much bombproof, so an external cause is most likely. The trunnion fixing the gear cable to the control lever may have snapped, so if the cable near to the gearbox lever does NOT move when the control, is moved (make sure the white tab that disconnects the gear linkage when in neutral is in the gear operate position), then take the control off to inspect where the cane is supposed to fix to the gear lever inside the control

[Traveller21]

Hi Tracy! I'm so so sorry, I had misread the email headers! We'll have a go with the advice given. Is it worth trying to shift the lever on the gearbox with the engine started as I doesnt seem to want to budge when it's off? 

Another maybe dumb question - would the gearbox have a separate oil filler cap than the engine? Ie, there is engine oil and gearbox oil? 

[Tracy D'arth]

4 minutes ago, Traveller21 said:

Hi Tracy! I'm so so sorry, I had misread the email headers! We'll have a go with the advice given. Is it worth trying to shift the lever on the gearbox with the engine started as I doesnt seem to want to budge when it's off? 

S'alright.

 

Yes, try it running but be careful of suddenly rotating parts. You have to disconnected the cable at the gearbox end because if it is seized/broken it will be difficult to move by hand.

The lever has a detent mechanism in neutral which takes a fair bit of pressure to move.

[Traveller21]

Thats what he's found so far - that the mechanism is seemingly jammed. I'll pass this onto him.....the detent mechanism is what is making it feel jammed. 

 

😄

[Alan de Enfield]

24 minutes ago, Traveller21 said:

Another maybe dumb question - would the gearbox have a separate oil filler cap than the engine? Ie, there is engine oil and gearbox oil?

 

 

Yes - the gear box has its own oil, oil filler cap, drain plug and its own dipstick.

The oil system is not connected in any way with the engine oil system.

[Traveller21]

Hi Alan,

Many thanks for that - this maybe the root cause of why it's happened/happening.....one lives and learns! 🙂

From an answer comes a question....

 

Which oil would be best for the gearbox? It's my son's boat - he filled the engine oil but didn't realise there was a separate gearbox oil 

[Tony Brooks]

10 minutes ago, Traveller21 said:

Hi Alan,

Many thanks for that - this maybe the root cause of why it's happened/happening.....one lives and learns! 🙂

From an answer comes a question....

 

Which oil would be best for the gearbox? It's my son's boat - he filled the engine oil but didn't realise there was a separate gearbox oil 

 

No, it is not, UNLESS a lack of oil has fused the astern clutch into a solid lump. When these run out of oil they just stick in neutral and won't engage either gear.

 

The ordinary engine oil, say API 15W40 in SAE CC to CE. Not synthetic.

[Traveller21]

It started with the tent getting fouled in the prop/screw - it may have had little or no oil in the gearbox? He'll locate the gearbox oil filler cap/dipstick tomorrow in the light and see what's in there.....if it's fused I'm guessing its a proper mechanic time?

[Tony Brooks]

1 minute ago, Traveller21 said:

It started with the tent getting fouled in the prop/screw - it may have had little or no oil in the gearbox? He'll locate the gearbox oil filler cap/dipstick tomorrow in the light and see what's in there.....if it's fused I'm guessing its a proper mechanic time?

 

It is exceptionally unlikely to be a fused clutch, because a lack of oil would make the box go into neutral.

 

Once he is sure the box will not work properly on the box's gear lever, that the cable and ends are intact, and the trunnion inside the control lever box is in place it would be a mechanic, but at present, on the info we have, I would say a cable problem is most likely.

 

On another matter. I hope it is just a hose, but one photo   can be read to give the impression that the alternator belt is very slack, ask him to check its tension.

 

[Traveller21]

Thanks Tony - we'll check this - I fitted the alternator a few months back (you may even recall the thread?)...and I can see it needs re-tensioning. The old one was fitted incorrectly and kept snapping the belts so at least we cured that one! 

[BEngo]

Looking at the close up picture of the gearbox operating lever:

The lock nut on the cable end is loose

The lock nut on the astern stop is loose. 

The operating lever looks to be bent against the gearbox casing.

 

The first two are not causing the problem, but will cause others if not correctly adjusted and fixed.

 

I think the third is probably the cause and is physically stopping the lever moving to neutral .  Cause probably  misuse as an unintended step whilst clearing the prop.  Disconnect cable, remove lever, beat it straight.  Do not attempt to bend it straight while fitted as this may well damage the input shaft seal.

 

N

 

[Traveller21]

I think you may well have a/the solution and many thanks for your looking at and responding to the problem we have. Hopefully next week being dry will give us a chance to have a proper look and get the thing sorted and back and up and running (and moving forward as well as back!). 

Thank you again,

Matthew 

[Bee]

Definitely agree with other posters that step 1 is to remove the cable from the gearbox operating lever and try moving that. If that is not possible then step 2 might involve spanners.

[Traveller21]

Thanks Bee - when the sun comes out again and the rain stops we'll get the cable off and see if we can get the lever moving again 🙂

[magnetman]

20 hours ago, Tracy D'arth said:

Has a foot been plonked on a cable or linkage?

 

 

 

Yes. 

[Traveller21]

Indeed! The cable has been damaged....so a new one ordered and being fitted this week and hopefully that should sort it 🙂