Prm gearbox replacement

[lexicon]

Looking for some advice.

Have a prm 100 gearbox which they stopped making in 1973 and looking into replacing in the not to distant future.

Have a bowman oil cooler for the gearbox.

Prm suggested that a 260 would be a replacement but looking for advice on how difficult it would be to replace? If the gearboxes are the same size input and output ends,

The engine is semi hard mounted.

Could it be done in a day by a competent workman ?

Asking times to get idea of labour costs

[alan_fincher]

Not answering your question, but.....

 

I thought I had noted in the pas you have a BMC 1.5 ?

 

If so, I would have thought that a PRM 260 (which is an excellent box, I believe) is considerably more than you need for the demands of that engine in a narrowboat installation.

 

I would have though the smaller PRM 150 more than adequate, and I think may well cost at least £500 less. Whilst the 260 will have a heavier construction and duty cycle, I doubt you need to pay the extra.

 

I have no idea whether one is a better straight swap for a PRM 100, (which I'm not familiar with), but the "100" sort of sounds like that was not a very heavy duty box in the first place, (certainly the 120 is the lightest duty of their current range).

 

Do you know the reduction of the current box, and is that of a suggested replacement the same. If not the prop is unlikely to still be suitable if it was before.

 

It seems some PRM 100 boxes, at least, were direct drive 1:1 ratio - you need to be sure yours isn't, I think.

 

Do you have a picture of the current box, and the details from its data plate?

[David Schweizer]

The PRM 100 Gearbox was discontinued in 1972, and the PRM Marine website indicates that it was replaced by the 260D, although it was badged as the 160D in those days.

 

:- http://www.asap-supplies.com/file_uploads/pdf/PRM-100-Spares-and-Repair-Manual.pdf

Edited February 11, 2013 by David Schweizer

[lexicon]

Hi Alan

Yes I do have a BMc 1.5

The prm 100 I have is a sizeable box

The data plate shows a 2.1 reduction.

The 260 Is listed as a replacement.

Looking for something that is a direct replacement to reduce issues of engine/prop adjustment.

As the more work it takes to fit a 160 the more labour I pay for other jobs associated

[Timleech]

Not answering your question, but.....

 

I thought I had noted in the pas you have a BMC 1.5 ?

 

If so, I would have thought that a PRM 260 (which is an excellent box, I believe) is considerably more than you need for the demands of that engine in a narrowboat installation.

 

I would have though the smaller PRM 150 more than adequate, and I think may well cost at least £500 less. Whilst the 260 will have a heavier construction and duty cycle, I doubt you need to pay the extra.

 

I have no idea whether one is a better straight swap for a PRM 100, (which I'm not familiar with), but the "100" sort of sounds like that was not a very heavy duty box in the first place, (certainly the 120 is the lightest duty of their current range).

 

Do you know the reduction of the current box, and is that of a suggested replacement the same. If not the prop is unlikely to still be suitable if it was before.

 

It seems some PRM 100 boxes, at least, were direct drive 1:1 ratio - you need to be sure yours isn't, I think.

 

Do you have a picture of the current box, and the details from its data plate?

 

I think the 260 will be the same physical size as the 100. Check with PRM, or find drawings on their site. Here, for instance. The input splines will almost certainly be different, so a new drive plate needed, but it would be a bit daft to fit a new box with an old drive plate. The output coupling should be the same.

Yes the OP could get away with a smaller box and save some money that way, but the engine mountings will almost certainly need to be moved or adjusted in some way so the saving might not be all that great especially if paying for the work. The 260 will be a better and more durable box than the smaller, newer models.

 

Edit to add that the gearbox adapter (mounting) plate might also need to be changed for a smaller box.

Tim

Edited February 11, 2013 by Timleech

[dor]

I replaced my Vetus gearbox with a PRM 150 in about 4 hours. That included resetting engine mounts, fitting the oil cooler and adjusting the Teleflex for the opposite direction.

 

It was the first time I have done it so any competent marine engineer should be able to do it in significantly less time.

[Timleech]

Hi Alan

Yes I do have a BMc 1.5

The prm 100 I have is a sizeable box

The data plate shows a 2.1 reduction.

The 260 Is listed as a replacement.

Looking for something that is a direct replacement to reduce issues of engine/prop adjustment.

As the more work it takes to fit a 160 the more labour I pay for other jobs associated

 

The 160 was an older version of the 260. I'm sure you meant 150 though.

 

Tim

[lexicon]

There seem to be 300ish difference in the two boxes and If a lot of adjustment needed to fit smaller box that will soon disappear in labour. Would a new drive plate with a 260 make it a simpler job ?

[alan_fincher]

I bow to Tim's far superior knowledge.

 

Yes, of course the 260 will be an even more durable box than the 150, so if the overall costings make it not significantly more expensive to fit, it sounds like it is a no brainer.

 

Normally, with nothing else factored in, there is a big price difference between the two, which would not be justified if oother costs were simiar, but Tim clearly knows the score in the case you are replacing.

 

Good luck

[RobinJ]

Looking for some advice.

Have a prm 100 gearbox which they stopped making in 1973 and looking into replacing in the not to distant future.

Have a bowman oil cooler for the gearbox.

Prm suggested that a 260 would be a replacement but looking for advice on how difficult it would be to replace? If the gearboxes are the same size input and output ends,

The engine is semi hard mounted.

Could it be done in a day by a competent workman ?

Asking times to get idea of labour costs

Think the 260 may be a direct replacement for the old one, even possibly with the drive splines?

Danger of changing for a different one would be height/position of output shaft and modification to mountings etc.

Need to check the orginal specs for old gearbox if still available, or take measurements and compare them to the specs for 260. Nice if your drive plate has a number on it, as this will tell you the input shaft fitted!

Some of the bellhousings are designed to take other boxes, others not, so you might find you need a new bellhousing too with a different gearbiox.

[Ray T]

Looking for some advice.

Have a prm 100 gearbox which they stopped making in 1973 and looking into replacing in the not to distant future.

Have a bowman oil cooler for the gearbox.

Prm suggested that a 260 would be a replacement but looking for advice on how difficult it would be to replace? If the gearboxes are the same size input and output ends,

The engine is semi hard mounted.

Could it be done in a day by a competent workman ?

Asking times to get idea of labour costs

 

We had a new gear box (PRM150) which replaced a Delta, October 2010.

 

Labour 8 1/2 hours £297.50 inc'l VAT

 

However this did include a new adapter plate.

 

We also had a new Centre Flex coupling and Plummer Block at the time as the original ones were cream crackered.

 

Time also included getting the whole engine and drive train re aligned

 

Hope this may be of some help.

Edited February 11, 2013 by Ray T

[RobinJ]

Could it be done in a day by a competent workman ?

Asking times to get idea of labour costs

Gearbox can be removed and replaced fairly easily if its a straight swap (hour maybe with drive flange/cooler piping and no complications!)

If the bellhousing has to be removed (more difficult with semi hard mounting), then could get involved, may be easier to take out whole unit and reinstall after changing gearbox?

Same is true if drive plate needs changing, depends on whether bellhousing needs removing or gearbox is bolted onto plate on rear of bellhousing (with access to drive plate).

 

Look at rear of bellhousing, does it have a lot of bolts around the outer edge or is the edge nearest the gearbox smooth and just bolts to engine?

[David Schweizer]

Not answering your question, but.....

 

I thought I had noted in the pas you have a BMC 1.5 ?

 

If so, I would have thought that a PRM 260 (which is an excellent box, I believe) is considerably more than you need for the demands of that engine in a narrowboat installation.

 

I would have though the smaller PRM 150 more than adequate, and I think may well cost at least £500 less. Whilst the 260 will have a heavier construction and duty cycle, I doubt you need to pay the extra.

 

I have no idea whether one is a better straight swap for a PRM 100, (which I'm not familiar with), but the "100" sort of sounds like that was not a very heavy duty box in the first place, (certainly the 120 is the lightest duty of their current range).

 

Do you know the reduction of the current box, and is that of a suggested replacement the same. If not the prop is unlikely to still be suitable if it was before.

 

It seems some PRM 100 boxes, at least, were direct drive 1:1 ratio - you need to be sure yours isn't, I think.

 

Do you have a picture of the current box, and the details from its data plate?

We have a PRM 160D (260D) fitted to the BMC 1.5 in Helvetia, it may be oversized but it will last for ever. It has been in the boat for 31 years, and has done about 22,000 hours so far. When the engine was re-buikt a few yeaers ago I asked the engineer to look at the gearbox as well, he stripped it, miced everything up and there had been no wear at all, he replaced the oil seals because it was easy to do at the time, and re-assembled it. The 260D is built like a tank.

[lexicon]

Thanks for all the advice.

[martyn 1]

Looking for some advice.

Have a prm 100 gearbox which they stopped making in 1973 and looking into replacing in the not to distant future.

Have a bowman oil cooler for the gearbox.

Prm suggested that a 260 would be a replacement but looking for advice on how difficult it would be to replace? If the gearboxes are the same size input and output ends,

The engine is semi hard mounted.

Could it be done in a day by a competent workman ?

Asking times to get idea of labour costs

 

The 160 is an upgraded version of the 100 and the 260 replaced both of these models. the 160 and 260 basically being upgraded version of the previous model. looking at the dimension drawings for all three models the only difference I can see it the input shaft on a 260 is longer than the 100 or 160. other than that the mounting bolt pattern matches. the distance of the drop center is the same on all three as is the overall fitted length.

 

So as far as I can see unless the extra input shaft length causes an issue in your installation. physically fitting a 260 should be very straight forward and quick to do (depending what is in the way on your boat) and the only "rework" would be to fit the controls and pipeing up to the slightly different arrangement fitted to the new gearbox

 

If you PM me I can send you the drawings for all three models and you can see for yourself

Edited February 11, 2013 by martyn 1