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When aligning an engine to shaft where there is no positive support on the inboard end it is almost impossible to know whether the shaft is central in the tube, particularly if the coupling is a heavy flexible unit like a Bullflex. As you disconnect the coupling the shaft can drop as the only positive support is the P bracket or other outer bearing which could be some distance away, so you can end up with the shaft in line with the engine, but not central in the tube.

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Well a way has to be found or the shaft will surely touch the tube. One method is described in Nigel Calder's book 'Marine Diesel Engines' which suggests attaching a spring balance to an overhead support and using it to lift the shaft with 50% of the weight of the coupling and half the shaft weight. It also says that in practice on a small yacht setup it is possible to estimate the dead centre height by feel/eye and to support the shaft with a block of wood with a vee in it at that height. Personally I like the idea of filling the gap with a single ring of gland packing, or as suggested by someone else with some tape wads.

The fact is that the shaft seal is a potential for major leaks if it fails. Whilst the Volvo seal will very probably do a temporary job it was never designed for that purpose and a wobbly shaft acting within it is a recipe sooner or later for uneven or faster wear. In my view that is a bodge and whilst I can bodge with the best I would not do it for something on which my boat and my family safety was depending. Sorry if that is harsh but that is what I think. In any case to swap the seal for a Volvo one will require a lift-out and surely having gone to that expense it would be best to do a proper job, and probably engage a competent professional engineer. To recommend anything else I feel would be risky.

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Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!

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