PRM 150 drain plug size

[DJW]

Simple question - can anyone tell me the size of the drain plug on a PRM 150?

 

We've just had one fitted and i can't find the correct socket to drain the oil at first service time. The largest socket I have is 19mm and the plug seems to be bigger than that.

 

Thanks

[PaulD]

According to the parts list it is an M16 drain plug so probably a 24mm socket. I can't see the hex size in the manual.

 

Maybe someone on their boat can check.

 

Paul

[jonathanA]

i think i do it with one of the imperial sockets in my small set - so it was either 11/16 or 3/4" can't remember. don't recall using any of my big metric ring spanners so its not as big as 24mm.

[Mickj]

if remember on my 500 box it is 19mm or 3/4

[Machpoint005]

It's an imperial size, definitely, but I can't tell you exactly which -- although I have a ring spanner of exactly the right size it's at the bottom of my toolbox on the boat. I realise that's not much help but don't use a metric spanner as it'll feck up the head.

[Mickj]

19mm is 3/4

[Machpoint005]

19mm is 3/4

No, it's fairly close to 3/4" but if you have a steel spanner, a brass screw head, and apply a large torque, the difference matters. The PRM manual suggests the screw plug is M16, but I think it depends how old the unit is.

[Keeping Up]

The manual that came with mine says it is an M16 nut which requires a 15mm AF spanner to remove it.

 

When you do get it off, and have finished changing the oil, don't screw it in too tight or it will be really difficult the next time. It doesn't rely on tightness, the rubber insert on the washer provides the seal so you just need to make sure it won't vibrate itself undone

[nb Innisfree]

At some point it changed from BSP to metric, or vica versa, can't remember which way.

[jonathanA]

The manual that came with mine says it is an M16 nut which requires a 15mm AF spanner to remove it.

 

When you do get it off, and have finished changing the oil, don't screw it in too tight or it will be really difficult the next time. It doesn't rely on tightness, the rubber insert on the washer provides the seal so you just need to make sure it won't vibrate itself undone

 

I think you might be getting confused with the level/filler plug which is also an odd size (18mm ?) on mine - I know a 17 is just too small and a 19 is just too big... and 18mm doesn't usually get included in most socket/spanner sets... of course they may have changed over the years

[john6767]

The filler is certainly 18mm, or at least that is what I use. I have not removed the drain, I pump the oil out. The workshop manual for the PRM 150 is here.

[Mickj]

I Think 18mm is 3/8 whit

[Keeping Up]

 

I think you might be getting confused with the level/filler plug which is also an odd size (18mm ?) on mine - I know a 17 is just too small and a 19 is just too big... and 18mm doesn't usually get included in most socket/spanner sets... of course they may have changed over the years

 

The manual says at para 7.1 (although I admit the wording does sound as if the writer was getting confused) :

 

"Drain all oil from the gearbox, the drain plug is located in the rear of the casing on the right hand side of the transmission. This requires a 15mm A/F spanner to remove" while the parts list shows it as "Item A15, Drain plug M16"

[jonathanA]

 

The manual says at para 7.1 (although I admit the wording does sound as if the writer was getting confused) :

 

"Drain all oil from the gearbox, the drain plug is located in the rear of the casing on the right hand side of the transmission. This requires a 15mm A/F spanner to remove" while the parts list shows it as "Item A15, Drain plug M16"

 

I think you might be right ! I particularly like the part where the manual says top up to correct level and THEN refit drain plug....

[dor]

My PRM 150 manual gives the drain plug as M16, which I believe is 27mm A-F, which is 1 1/16th inch to a thou or two.

[john6767]

My PRM 150 manual gives the drain plug as M16, which I believe is 27mm A-F, which is 1 1/16th inch to a thou or two.

I think M16 is 24mm AF.

[Captain Fizz]

The drain plug requires a 15 mm spanner. I have just checked it on the gearbox that is sitting on my workshop bench!!

[jonathanA]

The drain plug requires a 15 mm spanner. I have just checked it on the gearbox that is sitting on my workshop bench!!

 

just to round off the topic what size is the filler/dipstick ?

[dor]

I think M16 is 24mm AF.

I've just found this: http://www.thomsonrail.com/Technical%20Resources/A%20short%20guide%20to%20metric%20nuts%20and%20bolts.pdf

 

Which tells you almost everything you need to know about metric nuts and bolts. This does indeed say that M16 is 24mm across the flats. A site I found a year or so ago with a table of sizes which I copied and kept gave the M16 as 27mmAF - it would appear that they (and I) were wrong.

[john6767]

I've just found this: http://www.thomsonrail.com/Technical%20Resources/A%20short%20guide%20to%20metric%20nuts%20and%20bolts.pdf

 

Which tells you almost everything you need to know about metric nuts and bolts. This does indeed say that M16 is 24mm across the flats. A site I found a year or so ago with a table of sizes which I copied and kept gave the M16 as 27mmAF - it would appear that they (and I) were wrong.

Good, although this appears not relevant in this case, as it has been proved that it is actually a 15mm spanner that is needed. So the workshop manual is a bit misleading when is lists the drain plug as M16 on the parts list, as it must just be the thread that is M16, not the head. In fairness it does on the installation drawing show the filler as 18.0 A/F and the drain as 15.0 A/F, and in the list of tools it lists "Dipstick 18mm A/F" and "Drain plug 15mm A/F".

[Captain Fizz]

Yes, the filler/dipstick is indeed 18mm.

[DJW]

Just to add a little confusion....

 

I called PRM yesterday as mine is definitely not any of the above sizes. They told me the drain plug is 7/8" which equates to 21.75mm. I managed to undo it with a 22mm socket, which seemed a better fit than the 7/8" ring spanner I also had to hand.

 

This is a brand new gearbox and the guy at PRM went to measure one from their stock to be sure this was the most up to date size.

[n.b.Goldie]

I use a metric adjustable spanner. Had no luck with imperial adjustables. :-)

 

Regards

 

Ditchdabbler

[PaulD]

I worked for an American company and they used to send an imperial toolkit out with all their machines. As well as the imperial adjustable it also had an imperial hammer and imperial screwdriver.

 

Paul

[Flyboy]

^{I've changed the oil in my PRM 150 today and I can confirm that the drain plug is 22mm AF and the filler is 18mm AF.}

Edited October 15, 2013 by Flyboy