Jump to content

Noisy reverse gear?


lifeintheslowlanes

Featured Posts

Can someone explain why my reverse gear is noisy? I've noticed quite a few boats also make an odd sound when in reverse, so assume it's just how most gearboxes are designed? But what causes it to actually be like this?

 

Changed my gearbox oil a while back concerned there was something wrong with it but It just seems all narrowboats do a similar thing.... 

Link to comment
Share on other sites

9 minutes ago, lifeintheslowlanes said:

Can someone explain why my reverse gear is noisy? I've noticed quite a few boats also make an odd sound when in reverse, so assume it's just how most gearboxes are designed? But what causes it to actually be like this?

 

Changed my gearbox oil a while back concerned there was something wrong with it but It just seems all narrowboats do a similar thing.... 

What sort of gearbox is it?

 

MP.

 

Link to comment
Share on other sites

Its the hydrodynamics of the hull shape and the closeness of the prop to the peak of the swim, partially cavitation too.

Many gearboxes have a slightly different reduction ratio between for'd and aft and the output bearings are often designed to primarily take end thrust not reaction.

  • Greenie 1
Link to comment
Share on other sites

6 minutes ago, MoominPapa said:

What sort of gearbox is it?

 

MP.

 

PRM120 if I recall, deffo a PRM though, only a 2011 box with 1000 hours so not too old...

 

1 minute ago, Boater Sam said:

Its the hydrodynamics of the hull shape and the closeness of the prop to the peak of the swim, partially cavitation too.

Many gearboxes have a slightly different reduction ratio between for'd and aft and the output bearings are often designed to primarily take end thrust not reaction.

Ahh this was what I thinking of... interesting cheers!

Link to comment
Share on other sites

2 hours ago, lifeintheslowlanes said:

Can someone explain why my reverse gear is noisy? I've noticed quite a few boats also make an odd sound when in reverse, so assume it's just how most gearboxes are designed? But what causes it to actually be like this?

 

Changed my gearbox oil a while back concerned there was something wrong with it but It just seems all narrowboats do a similar thing.... 

 

There is no reason your gearbox should be anything but very marginally more noisy in astern than in ahead because the gear trains are very similar to car gearboxes. So I also go with hydrophonic noise. If the hardening has failed on any reverse gear teeth of on the reverse gear idler bearings it could cause noise but that is very unlikely.

 

Almost all older design of marine gearbox used a sun and two to four planet wheels all meshing and revolving in astern while in ahead no gears were used. This type of box makes a very noticeable whine in reverse even when in good condition.

 

 

 

  • Greenie 2
Link to comment
Share on other sites

29 minutes ago, Tony Brooks said:

 

There is no reason your gearbox should be anything but very marginally more noisy in astern than in ahead because the gear trains are very similar to car gearboxes. So I also go with hydrophonic noise. If the hardening has failed on any reverse gear teeth of on the reverse gear idler bearings it could cause noise but that is very unlikely.

 

Almost all older design of marine gearbox used a sun and two to four planet wheels all meshing and revolving in astern while in ahead no gears were used. This type of box makes a very noticeable whine in reverse even when in good condition.

 

 

 

Yeah as above it's hydrophonic noise I have been noticing. Gearbox itself is fine, just always had boats with outboards/drive legs in the past so haven't experienced it in the past, hence my slight worry which went a bit as I noticed loads of other boats doing it too.

Link to comment
Share on other sites

Changed the engine from a Lister SR2 TO a Isuzu with a PRM150. Never bothered to change the Lister prop(l.hand) for a right hand. Did thousands of lock miles with no trouble. If I remember correctly,the get you home ability(by locking the box)only works with a right hand prop(but you could lock it and get home backwards)

Link to comment
Share on other sites

12 minutes ago, nebulae said:

Changed the engine from a Lister SR2 TO a Isuzu with a PRM150. Never bothered to change the Lister prop(l.hand) for a right hand. Did thousands of lock miles with no trouble. If I remember correctly,the get you home ability(by locking the box)only works with a right hand prop(but you could lock it and get home backwards)

Just a comment. If you had kept the Lister box and drove it in reverse when going ahead it would very likely have developed terrible noise and then seized up or fallen apart inside. Lister boxes are Sun & planer wheel boxes and they react very badly to being driven in reverse for long periods.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.