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Jon57

Cracked blackstone box

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Hi. As tiilteled above my gearbox housing as developed a crack  how serious is this as I’m planning to go on the Trent shortly. No loss off oil. Is it repairable!!!! Thanks 

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Yes, anything is fixable if you spend enough

 

What engine is this gearbox attached to?

 

Richard

 

MORE: It's a bloody funny place for a crack, are you sure it isn't a scratch. Otherwise, I'm wondering if you have a gearbox adjustment problem

Edited by RLWP

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Hi Richard the engine is a jp3m . When I removed the bolt holding down the coverplate the bolt tread didn’t go right to the end like all the other ones . I think someone must have tried to tighten this bolt down and the unthreaded bit has done the damaged possibillly?? Just setting off so no internet for a while.

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8 minutes ago, Jon57 said:

Hi Richard the engine is a jp3m . When I removed the bolt holding down the coverplate the bolt tread didn’t go right to the end like all the other ones . I think someone must have tried to tighten this bolt down and the unthreaded bit has done the damaged possibillly?? Just setting off so no internet for a while.

That makes sense

 

If so, I can't see that it is going to cause much trouble or propagate

 

I think I'd either ignore it or do some kind of old fashioned repair at some time in the future

 

Richard

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3 hours ago, steamraiser2 said:

If you decide to go for a repair drop me a pm. We have a pile of them in the warehouse. Unlikely that we will ever use them

 

I must arrange to raid your warehouse sometime

 

Richard

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6 hours ago, steamraiser2 said:

If you decide to go for a repair drop me a pm. We have a pile of them in the warehouse. Unlikely that we will ever use them

 

Hi. Sorry for the late reply.Thanks for your offer will be in touch when l get back home in October.

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15 hours ago, Jon57 said:

Hi Richard the engine is a jp3m . When I removed the bolt holding down the coverplate the bolt tread didn’t go right to the end like all the other ones . I think someone must have tried to tighten this bolt down and the unthreaded bit has done the damaged possibillly?? Just setting off so no internet for a while.

 

This makes sense to me too. 

 

I would however leave that bolt out rather than put it back or better, get another without a plain shank. Or add a washer or two under the head to prevent the unthreaded section on the bolt reaching the threaded hole if you can't get the correct bolt.

 

Incidentally the term for a bolt without a plain shank is a machine screw, strictly speaking, IIRC. And a machine screw with a plain shank is a bolt :)  

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16 hours ago, steamraiser2 said:

If you decide to go for a repair drop me a pm. We have a pile of them in the warehouse. Unlikely that we will ever use them

 

I’m after some blackstone bits...at the moment all the bits that make up the external reverse stop....and possibly the shaped position plate...do you have those too? It’s for the 3G box as fitted to a JP2M. 

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13 hours ago, frangar said:

I’m after some blackstone bits...at the moment all the bits that make up the external reverse stop....and possibly the shaped position plate...do you have those too? It’s for the 3G box as fitted to a JP2M. 

We only have complete gearboxes here. Most of our customers ditch them in favour of our PRM conversion. I'll have a look but don't think that there are breakers there just entire boxes.

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It is unlikely that the stresses in use will extend this crack, its in a section that is not normally stressed. The problem would seem to be the bolt distorting the casting.

  I would give the crack a coat of paint, - I was serious- as it is open and find a bolt that is the correct length or put washers on it so it doesn't stress the crack when it is tightened.

The paint in the crack will seal it, Good old British Leyland used to paint transverse engine and gearbox assemblies to effect an oil seal. Under warranty they used to power wash the unit and paint it to stop nuisance oil leaks, it worked!

  • Greenie 1

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23 hours ago, steamraiser2 said:

We only have complete gearboxes here. Most of our customers ditch them in favour of our PRM conversion. I'll have a look but don't think that there are breakers there just entire boxes.

I'm a bit surprised by that. I accept that for a converted industrial engine it may be necessary to fit a modern hydraulic box, but I would have thought the sort of boater who chooses an older genuine marine engine would want to retain its original box if possible.

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8 minutes ago, David Mack said:

I'm a bit surprised by that. I accept that for a converted industrial engine it may be necessary to fit a modern hydraulic box, but I would have thought the sort of boater who chooses an older genuine marine engine would want to retain its original box if possible.

I would have thought so too! I like my blackstone....But there again I’ve heard people convert from the dry sump to a wet sump....just to save a few quid at an oil change...I just don’t get it personally!

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The reality is that 8 out 10 customers go for a modern box. Most chuck away the ram pump too. Vintage engine without the hassle is the usual reason although some cite their wife's preference for a lightweight gear change.  What I don't get is the virtual conversion of a JPM to match one of our industrial modifications. The industrial conversions are usually cheaper and none of them have ever seen the sea......you pays your money and makes your choice of course.

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On ‎20‎/‎08‎/‎2018 at 19:31, Boater Sam said:

It is unlikely that the stresses in use will extend this crack, its in a section that is not normally stressed. The problem would seem to be the bolt distorting the casting.

  I would give the crack a coat of paint, - I was serious- as it is open and find a bolt that is the correct length or put washers on it so it doesn't stress the crack when it is tightened.

The paint in the crack will seal it, Good old British Leyland used to paint transverse engine and gearbox assemblies to effect an oil seal. Under warranty they used to power wash the unit and paint it to stop nuisance oil leaks, it worked!

Remind me, why it was that Japanese cars wiped out the British car industry? !

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