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Learn About Sailboat Engine Gearbox Reconditioning

by:Mayer     2020-08-10
One small problem we encountered was how to get the four coupling bolts back into their respective holes once in position. They had wriggled out after some difficulty when removing the gearbox and we worked on the premise that what came out must go back in. However, on re-assembly the angle was so acute, there was no way they would line up sufficiently to access the holes in the gearbox coupling flange from the forward engine side. Well, as predicted, the best laid plans very often get interrupted - and so it is with our schedule for having the gearbox back into Patricks' yacht by this Saturday. Our gearbox expert Barry has completed the reconditioning and we have it back with us now. However, due to unforeseen circumstances we are unable to fit it this weekend and have put it back to Wednesday this coming week. Barry, of 'Marine Gearbox Services' is one of the very few and fast disappearing doyens of marine gear box maintenance, repair and reconditioning. With many years of experience under his belt there is no marine gearbox that he doesn't know inside out (excuse the pun) and never comes up short. His knowledge on all things gearbox is profound and being very particular in his approach you will always be assured of the best, and have complete confidence in his work. He showed and explained to us exactly what was causing the problem of the boat slipping out of and back into gear from time to time and what parts were worn and needed replacing. It is not the purpose of this article to supply a fully detailed manual of the work that needed to be done, suffice to say that friction clutch plates (sintered bronze) and steels were worn, the selector fork was too slack as was the selector ring. All these parts to be replaced along with the bearings, and all seals and gaskets. Any other parts Barry considered needed to be replaced as he worked through the job would be. Believe it or not, the Hurth gearbox does actually contain all those parts. It is difficult to believe that (a) that many bits are required for a simple forward and reverse gearbox and (b) they all fit into that limited space. It was a wise decision on our part to take it to the expert and not attempt to dismantle it ourselves. We had a very informative time with Barry and on coming away we wondered what will happen when all the Barrys' of this world stop their work - a rare breed indeed. In the meantime however, Barry is fully occupied with this work and not planning on giving it up any time soon. Having admired the re-conditioned gearbox with its brand new coat of paint from all angles and following several false starts (colds, 'flu and strong winds, big chop in a dinghy) Patrick and I find ourselves back on board and fully prepared to re-install the gearbox. Hunkering down into position in the cramped space we prepare for the long haul of heaving the box (heavy when you are kneeling in a cramped position and leaning forward) onto the engine bolts and then getting all the nuts and washers on and tightened correctly. My suggestion of going on through into the engine, removing the bearings and checking them was met with astonished incredulity! - they had been replaced previously and were fine, so my brand of humour was treated with the contempt it deserved! The only alternative (after much debate) was to bolt them up from the aft side with a spacer under the bolt head. This was tried on one, but as the lock nuts are half as thick again as the bolt head, we felt the clearance from the gearbox casing was insufficient - it was down to 1.5mm. In all probability this clearance was enough, but it looked way to fine for our liking and in its original position the clearance was around 3mm. What to do? In the end it was quite simple - we obtained some shiny new locknuts which Patrick ground down on his workshop grinder, taking off 1.5mm from the underside. Another dinghy trip out to the yacht saw us crunching down around the engine again and fitting the new nuts. Voila! they fitted perfectly, and with the additional spacer under the bolt head we now had 3mm. clearance between the nuts outer surface (the bolt end being flush with the lock nut) and the gearbox casing - looked much better, and along with peace of mind, it gave us confidence in a job well done. All that remained now was to couple to the 'drive saver' and the shaft coupling and this was a breeze. The gear cable strut was then bolted back into position and the gear cable attached ensuring it was placed in its correct groove. The moment of truth had arrived when it was time to start the engine and test that the gears would take up and operate correctly. With the engine on and running Patrick slipped it into the forward position - after a moments hesitation there was a satisfactory clunk and she was in gear - into neutral and into reverse - same clunk again and she was in reverse. Grins all round. Everything was working as it should so the kettle was put on and a sweeter cup of tea was never enjoyed more. Patrick has just returned from a few days sail up the NSW coast and reports that when motoring the gears are working perfectly. Lessons: With a little time and patience no job cannot be tackled on your own boat. Never be afraid to consult with the experts - in this case it was Barry of Marine Gearbox Services. When uncoupling the gearbox make sure you leave the four coupling flange bolts in position in the flange - this will overcome any problems when re-fitting.
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