BMC 1.5 GEARBOX WONT REVERSE

[Goldilocks]

Hello this is my first post here, I was driving my boat the other day and I lost the reverse gear, I took a look at it and noticed this part highlighted no longer moved into reverse when the throttle was pulled back into reverse. Any help?  Please ignore all the oil in the bilge I had an oil spill from the engine a few days ago which is all sorted now just need to clean up

[Jen-in-Wellies]

Welcome to the forum. The most likely cause is a broken gearbox actuator cable, sometimes called a morse cable. One end is attached to the lever you've circled on the gearbox. The other end goes to the combined gear and throttle lever. They lead a hard life and do break. If you can post a photo of the control lever we can advise on how to access the cable. A replacement is required. They are sold by the type of cable ends and the length. Easiest is to take the old one in to a chandlers and ask them to sell you a new one.

Will it go from neutral to forward and back OK?

[bizzard]

18 minutes ago, Goldilocks said:

Hello this is my first post here, I was driving my boat the other day and I lost the reverse gear, I took a look at it and noticed this part highlighted no longer moved into reverse when the throttle was pulled back into reverse. Any help?  Please ignore all the oil in the bilge I had an oil spill from the engine a few days ago which is all sorted now just need to clean up

The operating cable at 1o'clock on your yellow circle looks like it's very close or touching the exhaust silencer which light have melted the inner plastic sheath of the cable. Also check the outer cable clamp also at that location, two screws are tight. The same at the control lever at the helm.

[Goldilocks]

2 hours ago, Goldilocks said:

Hello this is my first post here, I was driving my boat the other day and I lost the reverse gear, I took a look at it and noticed this part highlighted no longer moved into reverse when the throttle was pulled back into reverse. Any help?  Please ignore all the oil in the bilge I had an oil spill from the engine a few days ago which is all sorted now just need to clean up

 

2 hours ago, Jen-in-Wellies said:

Welcome to the forum. The most likely cause is a broken gearbox actuator cable, sometimes called a morse cable. One end is attached to the lever you've circled on the gearbox. The other end goes to the combined gear and throttle lever. They lead a hard life and do break. If you can post a photo of the control lever we can advise on how to access the cable. A replacement is required. They are sold by the type of cable ends and the length. Easiest is to take the old one in to a chandlers and ask them to sell you a new one.

Will it go from neutral to forward and back OK?

Thank you for your help, I took a look at the cable leading from the gearbox to the throttle lever and noticed it had snapped clean off at the throttle end, I’ve removed it completely and now the gearbox part moves freely, will get myself a new cable and install soon. Thank you everyone for such a quick and helpful reply 👍 will keep this thread updated 

[bizzard]

5 hours ago, Goldilocks said:

 

Thank you for your help, I took a look at the cable leading from the gearbox to the throttle lever and noticed it had snapped clean off at the throttle end, I’ve removed it completely and now the gearbox part moves freely, will get myself a new cable and install soon. Thank you everyone for such a quick and helpful reply 👍 will keep this thread updated 

I wouldn't be surprised if the heat from the silencer melted the inner nylon sheath of that cable stiffening it too much which caused strain that snapped the cable. The blue plate to which the cable is clamped to might be moved to the left a little away from the silencer, but I can't see in your photo how it's attached. The silencer coould be turned a quarter turn to move it out of the way but looks too rusted to attempt it.

[hider]

Buy 2

Fit one

Keep one as spare

 

If you compare it to the throttle cable you may find that you can buy one that will fit both then you can have a spare for both.

Cables rarely wear out, they fail because of damage from heat from the exhaust, being installed with too tight bends or rust when the outer plastic is damaged and water gets in.

 

I am fascinated by that coupling behind that ancient PRM100 gearbox, I don't think I have ever seen one like it.

Edited December 18, 2024 by hider
additional

[Tony Brooks]

1 hour ago, hider said:

am fascinated by that coupling behind that ancient PRM100 gearbox, I don't think I have ever seen one like it.

 

A standard coupling supplied by either Tempest (the BMC marinisers) or PRM in the late 60's & 70's. It is a Mini drive shaft inner coupling in a pair of cast adapters.

 

Edited to add: Not a very easy design for doing engine alignment, the spider is held into the flanges by U bolts, so the two coupling faces often seemed to go out of alignment, and it was not so easy realigning them because it always seemed to move as you tightened the U bolts on one side. If there ever was a case for having a dummy coupling in its place when aligning, these where it.

Edited December 18, 2024 by Tony Brooks