prm gearboxes

A

alandav123

Well-Known Member
Joined
20 Sep 2006
Messages
140
Visit site
Hi all, I am pretty sure I have either a 302 or 402 marine gearbox bolted to a mercedez om 352 6 cylinder marine engine.
The gbox has a forward and reverse setting selected by a standard selector in the wheel house.
We moved her today and she seems sluggish and I would like to know if low, wrong type, water mixed gearbox oil could be the problem?.
Do these gearboxes have a power train as you would find in a transit van....meaning when the clutch is out and its in gear, a transit van supplies power even if thr oils low, wrong type etc. There's no fricton element to drive wheels, its metal all the way. I hope this makes sence.

Does the prm type box rely on thick oil to drag spinning plates around to spin the prop, OR is there a through train of metal all the way through making correct oil less important.

If the oils crucial, what type is it?.

Regards alan
 
The PRM hydraulic boxes work via clutch packs for each direction which are a series of plates alternatively splined to interna and external which are compressed by oil pressure which is supplied by an integral pump within the box.

Faults occur when oil pressure is lacking or the the clutch plates get worn you should have an oil pres gauge if not fit one

Low op would effect drive in both directions worn cluch pack only in the direction with the worn pack
 
boxes

Hi there, thank u so much for your helpful input. I have add'ed pics and there's clearly 2 pipes coming off top of gearbox. I assume' it is a hydrolic gearbox as you said. I am thinking tomorrow I should drain old oil and refill with hydrolic fluid and see if things improve. Then look to getting a gearbox oil pressure gauge,,regards alan
 
alandav123 said:
Hi there, thank u so much for your helpful input. I have added pics and there's clearly 2 pipes coming off top of gearbox. I assume' it is a hydraulic gearbox as you said. I am thinking tomorrow I should drain old oil and refill with hydraulic fluid and see if things improve. Then look to getting a gearbox oil pressure gauge,,regards alan
Click to expand...

the pipes go to a heat exchanger so oil is taken from the box passed through the cooler then back to the box
the oil will pass through the h/e the opposite way to the flow of water
it doesnt look like a PRM box to me
 
sailormam

Even ifs not a prm box...will I still be doing the right thing by putting hydrolic oil in it? I still don't know whether it needs gearbox oil, hypoidoil, automatic gearbox oil or something else.

A recomendation of a suitable oil would possibly sort it all out would be fantastic,
Regards alan
 
alandav123 said:
Even ifs not a prm box...will I still be doing the right thing by putting hydrolic oil in it? I still don't know whether it needs gearbox oil, hypoidoil, automatic gearbox oil or something else.

A recomendation of a suitable oil would possibly sort it all out would be fantastic,
Regards alan
Click to expand...

you need to know what box first
my PRM box is 15>40 as are the TMP box`s
 
Still not sure even if its PRM or not, someone said it does not look like a PRM.......I will have to get down tomorrow and identify the box 100% if its the last thing I do,,,,its a real pain. Thanks to all replies and I will post up again tomorrow. Regards alan
 
alandav123 said:
Still not sure even if its PRM or not, someone said it does not look like a PRM.......I will have to get down tomorrow and identify the box 100% if its the last thing I do,,,,its a real pain. Thanks to all replies and I will post up again tomorrow. Regards alan
Click to expand...

drain some oil / atf or what ever it is from the box then you will know what it had before
atf is quite thin often tinted red
 
sailormam

Hi there, sadly she took on quite a bit of water and maybe some got into gearbox, when I dip it the oil looks yelloyish but that could be salt water contamination OR its intact, pristene ( but a bit low) and its a hypoid special type oil, I just don't know, Regards Alan
 
It is a PRM box you use engine oil check the oil cooler
Drain the oil refill with fresh engine oil
bypass the oil cooler ie take one pipe off the cooler and the other off the gear box and attach first to gearbox will be ok for test purposes
 
Good afternoon All,
On the subject of PRM Box's
I have a PRM 402d marine transmission, I have found that I have milky oil, could well be a water leak from the cooler.
I can clearly see the drain down point.......but how do you refill????......please don't tell me it is through the dip-stick housing.
Also is there a seal set I can fit to prevent reoccurance.....it could be due to the fact the boat has been stood for a while in the French canals.
Any help or advice would be much appreciated.
D
 
My oil cooler tubes failed some years ago and water was getting into the oil of my PRM.

The oil itself was basically going out the exhaust as well ... which is my water / exhaust outlet. It would run fine with a top up of oil for about 5 - 6hrs .. then start being sluggish and finally no drive. Top-up and away we'd go again ...

I had to do this as I was halfway across the Baltic and very little wind ... meant I used quite a bit of oil to get home.

Once home - I used the Pela to suck what was now looking like yellow yoghurt ..... flushed with lightest oil I could get and sucked that out.
Pal of mine - I gave the cooler to .. he laughed when saw it - he then modified the internals and created a better tube assemble in the old case. Reckons his will outlast the boat !

But anyway - to OP ... yes water in the oil will most definitely cause the gearbox tyo act sluggish and in fact as water increases - may stop it from working ...

Oil to use in it ? same as you put in your engine .... no need to be fussy about it. Certainly not Hydraulic or Auto Transmission fluid which are as near same ... its far too light ....
A reasonable 10-40 ... 15-40 is fine.

I have the PRM Workshop manual if anyone wants it .. PM me as its too large for attachment here ...

It covers the 100 ... 175 ... 250 series.

I'm sure its available for download somewhere .. maybe manualslib.com ?

EDIT : Here you go :

PRM NEWAGE User Manuals Download | ManualsLib

And older :

PRM Older Models | PRM NEWAGE
 
Last edited:
You must log in or register to reply here.

Share this page

Top