red hot gearbox

[graycat]

red hot gearbox

 

 

Hi folks, I need a bit of help with a PRM150 gearbox fitted to a four year old 45hp Shire with over 5,000 hours on the clock,

Last year coming up the Trent against the tide I lost the drive due to the gearbox overheating, it got that hot some of the paint fell off the gear box casing, I got the boat moored up and changed the oil over night and managed to finish the journey with one more overheat, I have fitted a temperature gauge to the box now and on a short trip today found that it started to over heat ( up to 100 before I slowed down) , the engine temperature reads 80 on a run with no over heat problem so the only thing I can come up with is a blocked oil cooler could it be the tubes inside have got furred up?.

 

The gear box is working fine even though it got so hot the first time round

[steelaway]

red hot gearbox

 

 

Hi folks, I need a bit of help with a PRM150 gearbox fitted to a four year old 45hp Shire with over 5,000 hours on the clock,

Last year coming up the Trent against the tide I lost the drive due to the gearbox overheating, it got that hot some of the paint fell off the gear box casing, I got the boat moored up and changed the oil over night and managed to finish the journey with one more overheat, I have fitted a temperature gauge to the box now and on a short trip today found that it started to over heat ( up to 100 before I slowed down) , the engine temperature reads 80 on a run with no over heat problem so the only thing I can come up with is a blocked oil cooler could it be the tubes inside have got furred up?.

 

The gear box is working fine even though it got so hot the first time round

 

 

 

 

Hi

 

When did last change the oil?

 

Alex

[blackrose]

Does the gearbox have an oil cooler fitted?

[jelunga]

We have a Prm Delta. I will look and see if the handbook is any use. Back soon

[graycat]

oil cooler is fitted and the oil has been changed, I have had no trouble with overheating for the four years I have had the boat and I spend a lot of time on rivers so the engine is run faster than normal canals

[jelunga]

According to the handbook, which cover Delta, PRM 160,302,402 & 601, normal op temp is 50-70 deg C with max up to 80 deg C for short periods only. Fault finding chart gives following causes of overheating :-

Defective oil cooler

Oil cooler too small

Defective pressure relief valve

System blocked

Oil pipes too small.

 

If all has been fine for a long time you could discount cooler too small and pipes too small. I would look at relief

Valve and blockeage first.

[Timleech]

According to the handbook, which cover Delta, PRM 160,302,402 & 601, normal op temp is 50-70 deg C with max up to 80 deg C for short periods only. Fault finding chart gives following causes of overheating :-

Defective oil cooler

Oil cooler too small

Defective pressure relief valve

System blocked

Oil pipes too small.

 

If all has been fine for a long time you could discount cooler too small and pipes too small. I would look at relief

Valve and blockeage first.

 

If it's that hot, I'd say it's likely the ahead clutch is slipping. That might be just worn plates, 5000 hours is quite a lot, or an oil problem leading to insufficient pressure.

 

Tim

[n.b.Goldie]

Check that the oil cooler has been plumbed in so that the water passing thorough it does so on its way back from the skin tank and not from the engine.

 

The water from the skin tank will of course be cooler than the water coming from the engine. I seem to recall that at least one forum member found their plumbing to be the wrong way round resulting in the gearbox being heated rather than cooled.

 

Regards

Ditchdabbler

[alan_fincher]

If it's that hot, I'd say it's likely the ahead clutch is slipping. That might be just worn plates, 5000 hours is quite a lot, or an oil problem leading to insufficient pressure.

Yes, although OP says it is performing normally, other than overheating, surely one has to suspect it is slipping in ahead ?

 

Is the 150 box resilient enough for a 45 HP Shire being worked hard on river work, and with high engine hours ? That's a question, rather than a statement that it is not, but, even though PRM boxes are pretty tough, one might possibly have expected the next size up for this application ?

[blackrose]

I've got one running off a 55hp Isuzu, pushing a big boat on the river, but it's still fairly new.

[NBMike]

Check that the oil cooler has been plumbed in so that the water passing thorough it does so on its way back from the skin tank and not from the engine.

 

The water from the skin tank will of course be cooler than the water coming from the engine. I seem to recall that at least one forum member found their plumbing to be the wrong way round resulting in the gearbox being heated rather than cooled.

 

Regards

Ditchdabbler

That would be me I think. But its all sorted now. I replumbed the pump inlet and outlet and all works fine. I've even got my 'Redshaw' thermostat housing working as it should so - Tidal Trent here I come...........well, one day maybe!

Mike

[RobinJ]

If it's that hot, I'd say it's likely the ahead clutch is slipping. That might be just worn plates, 5000 hours is quite a lot, or an oil problem leading to insufficient pressure.

I had a similar problem some years ago, except it blew the seals by the time I got home.

Upon stripping it down and replacing the plates, I found the original retaining pins bottomed out on the thrust plate. The replacments had holes in the thrust plate to allow the plate retaining pins to pass through!

 

You mention an oil cooler, if this is fed from the skin tank, this can result in heating of the gearbox (or rather failure to cool) when thrashing along rivers! If this is the case it has probably exacerbated the underlying problem of a slipping plate.

[bottle]

I do not know if this is relevant but after Alan's post #9 and Blackrose #10. Taken from PRM website http://www.prm-marine.com/home.php

 

Nominal Power Ratings, PRM 150 Marine Gearbox

Pleasure 2.1 BHP (1.6kW) per 100 rev/min operating speed Commercial 1.5 BHP (1.1kW) per 100 rev/min operating speed Max. Input Speed 5000 rev/min intermittent, 4500 rev/min continuous

Note: These powers have been measured at the engine flywheel. Ratings have been established to ensure the long trouble free life of the gearbox which should not, therefore be used at powers in excess of those shown.

 

Service Classification Definitions - Pleasure Limited to craft used exclusively for pleasure boating; operation at full engine throttle should not exceed 5% of total time, with balance of usage at 90% of full throttle engine speed, or less. Maximum operation 500 hours per year. The selection of PRM150 according to this classification for any commercial boat is not approved by PRM Marine Ltd.

 

Service Classification Definitions - Commercial PRM Marine Ltd recommends that when considering the PRM150 in boats of whatever hull form used in commercial applications, and semi-displacement hull boats for pleasure applications, these boats should be classed as commercial duty and the gearbox selected accordingly.

 

[Keeping Up]

Check that the oil cooler has been plumbed in so that the water passing thorough it does so on its way back from the skin tank and not from the engine.

 

The water from the skin tank will of course be cooler than the water coming from the engine. I seem to recall that at least one forum member found their plumbing to be the wrong way round resulting in the gearbox being heated rather than cooled.

 

Regards

Ditchdabbler

 

 

That would be me I think. But its all sorted now. I replumbed the pump inlet and outlet and all works fine. I've even got my 'Redshaw' thermostat housing working as it should so - Tidal Trent here I come...........well, one day maybe!

Mike

 

Yes it would be me too. Before changing it around it was fine on most canals but always overheated on rivers. Luckily, for me the only symptoms were oil leaks and a need to keep changing the seals.

[luctor et emergo]

Am I the only one, severely dissapointed, after reading the topic title, to be confronted by a boring thread about an over heating gearbox...?

 

 

NO pictures..??

[Grace and Favour]

Am I the only one, severely dissapointed, after reading the topic title, to be confronted by a boring thread about an over heating gearbox...?

 

 

NO pictures..??

 

[MtB]

Am I the only one, severely dissapointed, after reading the topic title, to be confronted by a boring thread about an over heating gearbox...?

 

 

NO pictures..??

 

Yes I was vaguely hoping to see a pic of a PRM150 glowing bright red and illuminating the engine bay too!

[carlt]

Red hot gearbox

 

Yeah baby, Yeah!

 

Ooops, sorry, wrong window.

[by'eck]

Yes I was vaguely hoping to see a pic of a PRM150 glowing bright red and illuminating the engine bay too!

 

Here you are Mike

 

[bizzard]

It must have been stolen.

[graycat]

I must apologise for the total lack of photos of my red hot gearbox but it was the mighty Trent and I was occupied getting the life boat ready to launch and sending out maydays getting the cats life vests on

 

Am going to remove the gearbox cooler and see if it has got blocked in the tubes before removing the gear box.

 

Thanks for your help folks and will report on progress.

[Grace and Favour]

It must have been stolen.

 

It was no steal - - I'm sure they're aluminium

[Keeping Up]

It was no steal - - I'm sure they're aluminium

 

We had one that had half of the casing made of steel and half made of aluminium. As soon as it warmed up it leaked abysmally from the gasket between the two halves.

[bizzard]

We had one that had half of the casing made of steel and half made of aluminium. As soon as it warmed up it leaked abysmally from the gasket between the two halves.

Cohesion,often a problem when metals of dissimilar expansion rates are fixed together.

Edited February 20, 2012 by bizzard

[graycat]

Hi folks, I ran the boat in reverse for one hour and the gearbox remained at 65c, ran it in forwards and the temperature climbed up to over 100c, it must have been the forward clutch pack slipping, new box fitted now.