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Another gearbox in the Lister family, sharing features with the LH150 or LM100 but with more sophistication in the details At the heart is a reverse cluster made from straight cut gears: The main input shaft engages with the first set of planet gears in the centre. You can see the main shaft on the end of the crankshaft here: The other gears are the 2:1 drive to the camshaft on the left, and the governor gear and bob weights (top). Notice also that the lower half of the gearbox remains bolted to the engine while all the gearbox parts are removed. Also notice the oil in the bottom of the gear case which is shared with the engine sump. This is a Lister HB2 The gear cluster has two clutches, a band brake running on the outside for reverse, and a plate clutch in the centre locked by over centre levers: The centre shaft in the cluster passes through the drum to this spider assembly: The two keys in the centre and the teeth around the outside drive the boat when the forward clutch is locked. In detail, we have the spider: which drives the output shaft by the key in the bore. Onto that goes the driving plates: The teeth engage in the inside of the reverse drum. There are two of these plates, and they are made of some kind of phenolyic material. If you have a Lister Blackstone gearbox that drags in neutral, or stalls going into reverse, it may well be these plates being distorted. They can become conical and drag all the time Next, a cast iron plate keyed to the spider: Then another phenolyic plate, and the end plate: To illustrate how the clutch locks, here is the locking gear unlocked: and locked: On the outside of the mechanism are two levers with an adjuster on the outside. These are linked to pairs of links pointing to the centre hub. In the top view, the clutch is unlocked with the hub out and the pairs of links pulling the levers in. In the lower view, the clutch is locked. as the hub moves towards the clutch, the links push the levers out and the adjusters push down against the clutch pack, locking the clutch. Eventually, the hub moves so far forwards that the links over centre and start to push the hub towards the clutch instead of away from it. At this point, the clutch is engaged and the mechanism locked. It is this that holds the box in gear, not the external gear lever. Building this up in the drum: Spider: Phenolyic plate: Complete pack: Locking mechanism and retaining nut: Richard MORE: I can't add any more images to this post, could someone post something so I can start a new post?