BMC/Parsons

[Djh]

I have a 60yr old motor sailer originally powered by a BMC Commodore (circa 1957/8) mated to what  I believe to have been a Parsons reversing gearbox. Subsequently some genius decided to repower it with what  I think maybe a 4/98 Leyland. The gearbox held to the motor by 4 bolts! It fits where it touches. Having struggled to get it apart I've found that the stub shaft is 25thou out and the brakeband has worn a groove in the drum. There is no sign of a brake band lining. Mathway Marine suggested it might be a Morris Vedette gearbox. I didn't know BMC made their own marine gearboxes. Could it be a rebadged Parsons? I would like to get hold of a parts diagram and probably a manual if  I can gind out what it is. Did anyone ever marinize a 4/98 Leyland. If so  I might be able to purchase the correct bellhousing rather than having to have one made.

Any advice greatly appreciated.

[john.k]

There are a series of quite similar motors based on the good old Austin diesel tractor/truck motor.....basically 3.4l/3.8l/and the 4/98 .....respective bores being 95mm/100mm/and 98 mm.........so the story goes ,chief BL designer Red Ken decided to reduce the liner bore by 2mm to better align the engine with socialist working class theory........no better reason has ever been advanced............Anyhoo,as it be ,you can easily find a round #3 SAE housing to fit the truck motors ,and many boxes also fit the #3 housing............Morris Vedette is pre WW2,and therefore pre BMC.

[john.k]

A quick search finds two of the marine 3.8s being broken for spares.....many parts like housings and gears will be interchangeable.......if yours is actually a 4.98 and not a 3.4 or 3.8,then the breakers might be a source of free information......if they thought you were looking to buy.

[Tony Brooks]

I am sure it is a BMC B type marine gearbox and prolbay based on a Parsons design. Almost certainly pre abut 1970s. I fear changing the box for something more modern would be the easiest way although you may need an adaptor plate machining. I think you have the input shaft bolted to the flywheel mounting bolts so that would need changing for a drive plate. maybe worth Ringing Chertsey Meads Marina just in case  they are breaking an old BMC lump.

 

If you are very lucky perhaps @RLWP may be able to assist (Primrose Engineering/MES (Midlands).

 

Edited to add: It is possible that you have a BMC DCC (C type) but as far as I know they do not have a brake band but they seemed to have been popular in your part of the world.

 

Here is an image of a BMC C type although the vendor claims it is a B type:

 

The B type has the control ever mounted on the side of the box and not on top of a turret as in this image. You can also see the linkage to operate the automotive clutch going o the bell housing. I don't think you have a flywheel mounted clutch on yours.

 

To clarify a point. I am sure that post war the BMC A type petrol engine was sold as a Vedette but i think they would have had the BCA (A type) gearbox that is similar to the B type.

 

B type with reduction box:

 

 

 

A type on BMC Vedette

 

Edited November 2, 2021 by Tony Brooks

[Alan de Enfield]

I guess it wouldn'tbe cheap to ship a great lump of a gearbox from the UK to New Zealand.

Maybe try breakers in NZ or Aus to see if they can help.

[Tony Brooks]

5 minutes ago, Alan de Enfield said:

I guess it wouldn'tbe cheap to ship a great lump of a gearbox from the UK to New Zealand.

Maybe try breakers in NZ or Aus to see if they can help.

 

FWIW,  a couple of years ago I had correspondence from Australia about a BCC box and the owner found it viable to import one from the UK.

 

Back to the OP's question. I have a faint idea from memory that the brake band in the B type did not have a lining but can't be 100% sure.

[Awayonmyboat]

From experience of shipping motorcycle engines between UK and Australia I can confirm it is expensive. But shipping the same across Australia or between Australia/NZ is also surprisingly expensive. So if OP cannot find what they need in country it could make sense to ship from the UK (albeit there is a risk of unexpected duties which can upset the financial calculation a bit).

[Tony Brooks]

As  the thing is so old  and obsolete yet not yet an antique I would suggest the thing would have no commercial value for the customs declaration.

[Djh]

Thankyou all for your help and interest. I have uploaded an album of photos onto thumbsnap but have been unable to share them. I have cotacted them for a 'how to' but so far have not had a reply. Hopefully willbe able to do so shortly which should make things a lot easier.

[Tony Brooks]

2 hours ago, Djh said:

Thankyou all for your help and interest. I have uploaded an album of photos onto thumbsnap but have been unable to share them. I have cotacted them for a 'how to' but so far have not had a reply. Hopefully willbe able to do so shortly which should make things a lot easier.

 

You can put the web address of your album into a post her like www.thumbsnap.xx/yyyyyyyyy. or for a single small photo or may be two can be directly loaded into this site. look at the bottom of the screen you use when composing your message. When I say small I mean low resolution.

[Djh]

Thankyou Tony.

[Djh]

I have created albums (8 pics) on: Google Photos, Flkr and Thumbsnap. All have the album title: BS motor & gearbox. Hopefully anyone registered and using one of these apps will be able to view them.

[Tony Brooks]

2 hours ago, Djh said:

I have created albums (8 pics) on: Google Photos, Flkr and Thumbsnap. All have the album title: BS motor & gearbox. Hopefully anyone registered and using one of these apps will be able to view them.

 

That won't be me then an possibly I am your best bet in identifying the box now RLWP does not visit as much. Why can't you put a couple on the forum so we all can see them? If they are too large and you don't have the resources to make them smaller, i understand other take a screenshot of the thumbnail or find the thumbnail file and post that

[Tony Brooks]

Thinking about this a bit more I am not so sure that in view of how the modification is described that it is a BMC B type. I say this because I am 98% sure (been over 50 years) that that box has a front plate that is sandwiched between the box body and the flywheel housing. The box is very heavy and from my memory I doubt that plate  would allow the conversion as described. In any case the BMC box does not use a drive plate. The input shaft that has a sun gear cut into it bolts directly to the crankshaft. I also think that plate carried a bearing (plus oil seal) that supported the front of the whole clutch, drum, and planet gear assembly so again it makes the conversion less likely.

 

Yes the 4.98 was marinised and there are some images, sans gearbox, on Google. It seems it is just a standard BMC 3.8 diesel from Google. Even if you do find a bell housing you would be very lucky if your gearbox bolted straight onto it, you may need an adapter plate and/or possibly another gearbox.

 

Be wary about online adverts. On old stuff they are often misidentified like the supposed B type box that I amsure was a C type. I have just found a 3.8 described as a BMC Sea Lord.. I think the Sea Lord was the six cylinder engine so that one is wrong as well.

 

The naming of the BMC marine engines  went like this: 998 is petrol - Vedette, 1500 petrol - navigator, 1.5 diesel - Captain, 2.2 and possibly 2.5 diesel - Commander, 3.x diesel - Commodore (as you say), and the six cylinder (5.1?) diesel - Sea Lord.

 

After more thinking I ma not sure that you need to worry about the groove in the drum until the drum falls apart. I very much doubt you will find one and if you do that might be grooved as well. Just be pragmatic.

 

I can probably explain the adjustment of a B type box and if you have any other symptoms suggest possible causes. The B type box is very typical of the general design of marine boxes of the time so many look very simmilar inside.

 

 

[Djh]

[Djh]

Hi Tony. Have been messing around for 3 days trying to get photos onto the site. Finally. As someone suggested I also contacted Lancing Marine who suggested it might be a Newage. There was so much rebranding going on in the day that it all gets a tad confusing. If  I can identify the box I may be able to get a service manual for it . At the moment it is fighting us every step of the way. It definitely does not want to be dismantled. As you would expect there is a fair bit of wear in the gear bushings and 1 of the gears inside the brake drum has a broken tooth. I presume the carnage list will increase as we progress. Very much appreciate your input and help.

Forgot. All casting marks/parts numbers, internally and externally on the gearbox start with AEH.

[Tony Brooks]

Definitely looks like a BMC B Type to me but I don't know if it was related to Morris or Austin pre BMC.

 

Any half decent machine shop should be able to re-bush the gears. Remember those gears only rotate in reverse. In ahead the whole drum spins as a sold assembly. The long bolts that hold the clutch assembly into the rum seem to suffer fatigue failure so maybe it would be a good idea to fit new if you rebuild it. No idea how to deal with the broken gear teeth for a reasonable cost, but as it is just one of a pair maybe you could put up with the extra noise in reverse. That style of box  always seem to whine in reverse, even when new and run in.

[Djh]

Hi Tony. Thanks for your info. On reflection the damaged gear is missing 1/3 or less of the operating surface of 1 tooth. 2 gears have nonexistent bushing and others badly worn. I have a local machine shop , run by an expat Yorkshireman who is very good, but as he said today the price of bronze is going through the roof. Still need to get the rest of it apart to fully assess damage before I can make a decision. At least I can now look for an appropriate manual. Thankyou.

[Tony Brooks]

I think the B type had a plunger oil pump with integral jet mounted on the intermediate plate between gearbox and bell housing with the jet pointing into the sun & planet gears. It was driven from an eccentric on the input shaft that is  bolted to the flywheel. I can't see any signs of the input shaft or the intermediate plate. The planet gears were never well lubricated and if the conversion did away with the pump or if you have the wrong handed prop and run the box backwards that might, in addition to pure old age, contribute to the bush wear.

 

I know it is not any sort of good practice but if you accept the box is obsolete and is likely to need replacing sooner rather than later I don't see why the bushes cant be brass as long as they put an oil groove in them. I also fear the ahead clutch plates may be in a very bad way but time will tell.

[Tony Brooks]

Further thoughts re the chipped tooth.

 

When putting the gearbox back onto the engine you have to align the gear teeth on the input shaft with the gear teeth on the planet wheels. The easiest way we found on one with a  reduction box was to manually turn the engine over while pushing the box into place. I suspect that tooth may well have been chipped when someone tried to force the box on without aligning the teeth. I can't see how else it could happen unless some debris got left in the box or a head fell of one of the long clutch bolts, but even then I think it unlikely.

 

Whilst on the topic you need to take care that you start to refit the box with the eccentric on the input shaft low where the oil pump plunger sits.

Edited November 9, 2021 by Tony Brooks

[Djh]

Thankyou Tony. You are absolutely correct. The box does have a plunger type oil pump on an intermediate plate with a central bearing. It was this bearing that took the 1st line of abuse because the stubshaft was at least 25 thou out. It took a 40ton puller to move it. The brake drum is proving similarly recalcitrant at the moment and resisting all efforts to shift it. An ongoing saga I fear. Will hopefully get easier once I obtain a workshop manual now I have gearbox id.

[Tony Brooks]

I don't think I have ever seen a manual just fro that gearbox. The "manual", such as it is, was in the back of the engine manual, but that was for the original BMC marine engines. Commander or Commodore and just possibly the Captain.

[Djh]

Funny you should mention that. Yesterday I found a bmc commander for sale on a local trademe site and low and behold one of the pics showed an owners workshop manual for a Newage Commander engine. Ive sent him a cheeky question asking if it has any mechanical box info in the back of if. That particular engine has a velvet drive box with a Lancung Marine badge on it.

[Tony Brooks]

14 minutes ago, Djh said:

Funny you should mention that. Yesterday I found a bmc commander for sale on a local trademe site and low and behold one of the pics showed an owners workshop manual for a Newage Commander engine. Ive sent him a cheeky question asking if it has any mechanical box info in the back of if. That particular engine has a velvet drive box with a Lancung Marine badge on it.

 

I hope it does, but Lancing was not the "official" BMC mariniser so that might be why it has a Velvetdrive box.

[Tony Brooks]

I think, and it is only think, that the drum comes out as part of the output shaft so the reduction box needs splitting the the reduction box input gear removing form the shaft. Once the whole assembly is out I think that if you remove the long bolts that hold the ahead clutch assembly together the drum and gears will all come apart. Don't hold me to this though, I am going back over 50 years of memory.