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Lister Blackstone 3G Gearbox


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Just bought new boat (well new to me anyway) it has a JP2 circa 1936 with a Blackstone 3G gearbox.  Using push/pull rod to change gear it slips out of gear when in forward motion unless you keep pressure on rod (it tends to creep backwards and slip out of gear.   Same in reverse - have to keep pulling pressure on rod to keep it in gear.

Suspect I need to check reverse and forward adjusters in the Blackstone.   Does anyone know if they can be accessed and adjusted with just the top plate removed from the gearbox or do I have to split the gearbox in half and remove top half of casing?

Also what type and thickness of gasket is used?

Any advice greatly appreciated.

 

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8 minutes ago, Saint Paul said:

Just bought new boat (well new to me anyway) it has a JP2 circa 1936 with a Blackstone 3G gearbox.  Using push/pull rod to change gear it slips out of gear when in forward motion unless you keep pressure on rod (it tends to creep backwards and slip out of gear.   Same in reverse - have to keep pulling pressure on rod to keep it in gear.

Suspect I need to check reverse and forward adjusters in the Blackstone.   Does anyone know if they can be accessed and adjusted with just the top plate removed from the gearbox or do I have to split the gearbox in half and remove top half of casing?

Also what type and thickness of gasket is used?

Any advice greatly appreciated.

 

 

You can get at the adjustments under the the top plate. For forward there are two, 180 degrees apart on the clutch, Reverse is on the end of the rocker.  Both of these are over-centre, so they shouldn't come out once engaged. There should be a sector-plate on the outside of the box behind the gear lever which has three adjustments, it can slide back and forward on the mounting bolts and there also are two stops, one for forward and one for reverse. The aim is that the two stops provide a definite limit to the travel of the gear lever to avoid strain on the internal parts of the box, but if they're not letting the lever travel far enough, you won't get to the over-centre part of the travel and that could cause the symptoms you're seeing.

 

MP.

 

 

 

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Be very very carefull adjusting the internal adjusters on a blackstone. i believe its 1/4 of a turn at a time.

 

how do i know this ? An engineer friend used one of our boats in 1985. Coming through hopwas shallows he thought the clutch was sticking. Manual in one hand spanner in the other he gave forward a tweak.

started up put in gear and the drive plate exploded, taking out a few other bits.

 

he sourced new parts from australia and south africa and bolted it back together.

 

Ran fine to 2000 when we sold her.

 

To this day its one flat at a time adjusting the box.

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It may be( because you are new to the boat), that you are just not pushing the lever in far enough ir pulling it out enough for it to lock.

I was bringing a boat out of Brinklow in a gale a few years ago and couldnt get off the pontoon as the gearbox didnt seem to want to work. Rand the owner and his advice was " push the handle almost into the bathroom"!!! 

I did, and it worked.

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54 minutes ago, matty40s said:

It may be( because you are new to the boat), that you are just not pushing the lever in far enough ir pulling it out enough for it to lock.

I was bringing a boat out of Brinklow in a gale a few years ago and couldnt get off the pontoon as the gearbox didnt seem to want to work. Rand the owner and his advice was " push the handle almost into the bathroom"!!! 

I did, and it worked.

That was me ! Yes long arms needed:)

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