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the gearbox on my little springer 23ft i think is on its last legs as forward gear is slipping badly...  its a hurth 50 mechanical box from what i can tell..  does anyone know where i can get it reconditioned or buy a replacement...  will the prm90 box be a direct fit?   any advice would be great....

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It isn't usually worth repairing those little Hurth boxes. By the time you add up parts and labour, you are very near the price of a new box

 

You can check the shaft and bolt spacings here: http://www.wbryant.com/temp/hurth_manual.pdf

 

And for the PRM 90 here: https://www.prm-newage.com/media/uploads/582037ddd8fbb.PDF

 

Richard

 

 

Edited by RLWP

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thankyou for the links...       just wondering if anyone has done the conversion on here?     ive found a used hurth box for not alot of money so might risk it and if no joy then a new box it is...

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21 minutes ago, crosser said:

thankyou for the links...       just wondering if anyone has done the conversion on here?     ive found a used hurth box for not alot of money so might risk it and if no joy then a new box it is...

 

I'm feeling too idle to do the check properly. From memory, most of these small boxes use the same bolting pattern and spline sizes so they should be an easy swap

 

No guarantees, mind. I've found you the information you need to work it out

 

Richard

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1 hour ago, RLWP said:

 

I'm feeling too idle to do the check properly. From memory, most of these small boxes use the same bolting pattern and spline sizes so they should be an easy swap

 

No guarantees, mind. I've found you the information you need to work it out

 

Richard

 Can't remember either.

If you are mechanically savvy, replacing the forward clutch is not difficult or expensive, done loads. 

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i did think about that until i got a price for new plates..  £470...      gulp !!

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What! Its been a while but I never paid anything like that. Is that just for a clutch kit? Crazy profiteering if it is.

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3 minutes ago, crosser said:

i did think about that until i got a price for new plates..  £470...      gulp !!

Most of the parts on the main shaft are a push fit making the job pretty tedious too. Especially when getting the ball clutches together

 

Richard

2 minutes ago, Boater Sam said:

What! Its been a while but I never paid anything like that. Is that just for a clutch kit? Crazy profiteering if it is.

https://www.asap-supplies.com/engine-spares-gearboxes/marine-gearboxes-and-spares/marine-gearbox-spares/hurth-gearbox-clutch-plate-kit-107620

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2 hours ago, crosser said:

thankyou for the links...       just wondering if anyone has done the conversion on here?

I became less idle...

 

The mounting holes are the same on the PRM 90, the shaft is the same, although perhaps 10mm longer. The output flange is the same, What I can't find is the overall length of the PRM90

 

What engine is this going on?

 

Richard

 

 

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Hells breath, they have gone up a bit.

Another reason not to like Hurth boxes.

 

Of course ZF Hurth is a German company I think, brexit revenge starting early? Or is Germany in such a parlous state that they need the money?

A new box wasn't that much in the '90s I think.

 

Last year I bought a 280 PRM hydraulic box which is a big bomb proof cast iron lump of a gearbox brand new for £1300, no comparison is there?

Edited by Boater Sam

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thankyou richard for finding that out for me...   its to fit on my nanni n21 (kubota 3 pot)....   i think the prm90 is looking best bet ..  i cant believe how rubbish the hurth boxes are and the price of spares..    thanks again...

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I found a new 125 Hurth, a lot bigger box, for  £798 so the price for spares for the clutches which are all the same is a shocker.

The PRM 90 uses a cone clutch, better.

Ensure that your tickover is not too high, straight mechanical gearboxes can engage with a damaging snatch which does then no good at all. Likewise avoid rapid shifts from forward to reverse, pause in neutral whilst the engine revs drop.

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8 minutes ago, crosser said:

thankyou richard for finding that out for me...   its to fit on my nanni n21 (kubota 3 pot)

Like this?:

 

https://www.mshs.com/pdf/Products/Nanni/Brochure N3.21-ENG.pdf

 

The PRM 90 spec is here: https://www.prm-newage.com/p40-prm90

 

It gives two specs for the gearbox, 'pleasure' and 'light commercial'. If that's the right engine, the gearbox easily covers 'light commercial'

 

You'd think canal work is 'pleasure', unfortunately the continual forward/backward of lock work isn't at all like sticking a boat in gear to go fishing. 

 

Looking good

 

Richard

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thats brilliant ....   i think i will check on the prices for a prm90 and get a quote to fit as it will probably need fettling...    is a cone box smoother to operate as mine does clunk when going into reverse and used to when going into forward until clutch started to slip...  

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2 minutes ago, crosser said:

thats brilliant ....   i think i will check on the prices for a prm90 and get a quote to fit as it will probably need fettling...    is a cone box smoother to operate as mine does clunk when going into reverse and used to when going into forward until clutch started to slip...  

Not in my opinion, if money were no problem I'd be looking to fit a PRM150. 

 

However, the PRM90 will do the job. What is most likely to need fettling is the bracket for the operating cable. The Hurth one is unlikely to fit the PRM

 

Richard

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ive just found a prm150 on ebay thats been rebuilt by primrose for £450...   hmmm..  decisions

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1 minute ago, crosser said:

ive just found a prm150 on ebay thats been rebuilt by primrose for £450...   hmmm..  decisions

:D

 

You need to do the installation sums again to be sure you don't need a different adapter, make sure you don't have to raise the engine or shorten the propshaft, you will need to buy and install an oil cooler and hoses....

 

There are a lot of incidental costs over the PRM90

 

Richard

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51 minutes ago, RLWP said:

:D

 

You need to do the installation sums again to be sure you don't need a different adapter, make sure you don't have to raise the engine or shorten the propshaft, you will need to buy and install an oil cooler and hoses....

 

There are a lot of incidental costs over the PRM90

 

Richard

I've heard primrose do a decent job on gearboxes 

 

;)

 

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Another one in the dont buy a reconditioned Hurth gang.

1st one wouldn't go into forward, 2nd wouldn't go into reverse, so a new one purchased (MS), lasted 12 hours before eating itself so the PRM swap done and boat has been fine since.

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So don't buy a new one either seems to be the score.

23 minutes ago, matty40s said:

Another one in the dont buy a reconditioned Hurth gang.

1st one wouldn't go into forward, 2nd wouldn't go into reverse, so a new one purchased (MS), lasted 12 hours before eating itself so the PRM swap done and boat has been fine since.

We use the PRM 80 in a day boat, needed a new one every second year but the poor thing got hammered. Put a 90 is the last time, it lasted better. Hurth wouldn't have got back after the first trip.

Edited by Boater Sam
added more

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its sounding like i should just go for the prm90...     from what ive read the engine needs to be raised 10mm on the mounts to fit it so will have to check if its possible on mine...   i dont think ive read a good thing about hurth boxes....   mind you alot of it seems to be reconditioned boxes giving problems, maybe just inferior parts compared to original bits...  

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Hurth gearbox on my boat,(BMC 1500)  was on when I bought it.

Two years and I have done some 500 hours and it's been no bother.

Have read somewhere that the Americans call it the dollar an hour gearbox,because it used to cost $1000 and last about 1000 hours.

 

 

 

 

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21 minutes ago, Mad Harold said:

Hurth gearbox on my boat,(BMC 1500)  was on when I bought it.

Two years and I have done some 500 hours and it's been no bother.

Have read somewhere that the Americans call it the dollar an hour gearbox,because it used to cost $1000 and last about 1000 hours.

 

 

 

 

You are doing well but 500 hours is really nothing, many boats do twice that a year.

I would guess that you have your BMC 1.5D tick over very low, this helps as its the take-up snatch with mechanical gearboxes that shortens their life.

In relation to what you can buy a PRM hydraulic box for ZF Hurths  are terribly expensive.

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i think im going to go for a new prm90 as thats all i can afford...   how long or much do you think it will cost for fitting so i know if im getting stung or not...   thanks again

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If you were near us it wouldn't take long...got it down to a tee now like a formula 1 wheel change....we've done it that much in the last few weeks. Once the gearbox is onsite, 2 hours tops unless theres something else that has to be removed to get to the box ( exhaust, pipes, wiring, etc.). 

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