| The gearbox on a friends' yacht started playing up | | | | good, with all nuts undoing reasonably easily. |
| recently. It is a simple Hurth box with a three position | | | | Now, we come to what is to prove to be the most |
| gear lever - forward, astern and neutral - which is all | | | | heat generating part of the operation, and that is |
| you need for the average sailboat. From time to time it | | | | uncoupling the shaft from the coupling plates. The shaft |
| would slip out of gear when going forward and then a | | | | needs to be slid back toward and through the stern |
| few seconds later it would grab again and go back | | | | gland about eight centimetres, to allow for the coupling |
| into gear. This was ok for a time, but it was noted that | | | | plates to come off and the gearbox to be worked off |
| as is always the case, these malfunctions gradually | | | | its studs on the bell housing. It doesn't want to budge. |
| deteriorate and become worse, never better, and that | | | | Nothing generates heat more quickly than two |
| at some point in the future it would need some | | | | amateur mechanics in a confined space heaving on an |
| attention. Sure enough it gradually got worse and was | | | | obstinate piece of machinery that doesn't want give up |
| staying longer out of gear before going back in again, | | | | its purchase. The shaft has been quite happily rotating |
| to the point where the decision was made to take | | | | whilst driven by the engine, but once de-coupled does |
| some positive action. | | | | not wish to be turned by hand and definitely not |
| Apart from this being potentially dangerous i.e. not | | | | wanting to be slid sternward into and through the stern |
| being able to go astern when docking etc., or | | | | gland. |
| subsequent damage arising from being unable to avoid | | | | The shaft has obviously bedded itself into the stern |
| a collision when under power, it is good seamanship | | | | gland packing and lodged in a comfortable position |
| practice to keep right on top of these maintenance | | | | from which it objects to being changed. The next step |
| jobs when they occur - not much later when they | | | | is to dig out the gland packing and this is laboriously |
| could potentially put you, your boat, your crew and | | | | achieved with a sharp screwdriver and time. It has |
| others at risk. This particular gearbox is a simple Hurth | | | | been awhile (ten years) since the gland was packed |
| (Hurth 150) one speed box attached to a marinised | | | | so it was stiff, hard and dry. With the gland packing |
| Perkins 4108 (48hp) diesel engine of hazy history. The | | | | removed and using the largest lever available we |
| boat was built in 1988 and the engine could well have | | | | attempt to separate the shaft from the coupling plates. |
| had hours on it prior to it being marinised. The Hurth | | | | It moves about half a centimetre and stops once |
| would have been fitted new at that time and twenty | | | | more. Several sweaty minutes later and a combination |
| five hundred hours have been run on the combination | | | | of levering between the plates and a large driver |
| in the ensuing years. | | | | rotating the coupling plates from side to side the shaft |
| Following a considerable amount of research we have | | | | head plate and shaft is worked back five to six |
| located a marine engineer who can service and | | | | centimetres. |
| recondition the gearbox providing we can get it to him. | | | | This looks ok but we were to find out later it was not |
| This is the point we are currently at now, and facing up | | | | quite far enough. The next task is to unbolt the coupling |
| to diving into the bilge to uncouple the shaft from the | | | | plates. These are very cunningly bolted from both |
| gearbox and remove the gearbox from the engine. | | | | directions and neither set of bolts have enough room |
| The date has been set and all going well we should | | | | to fully exit their respective plate. This was where we |
| have it out of the boat and to the engineer by the | | | | discovered the shaft and its plate had to go a little |
| afternoon of Tuesday 14th April. | | | | further aft. By this time we knew what we were doing |
| Easter has arrived and true to form we are | | | | and a couple of good heaves and it was done. With |
| experiencing classic Easter weather - overcast, | | | | much debate as to how to remove the bolts from the |
| drizzling rain, but warmish - it never fails, no matter | | | | coupling plates, many minutes later and a lot of |
| what time Easter falls! That being the case we | | | | wriggling they came away. It was at this point we |
| brought forward by one day the task of stage two of | | | | began speculating on how we were going to |
| our removing the gearbox project (challenge) - never a | | | | re-assemble them! Cross that bridge when we get to |
| bad idea when you are dealing with mechanical people | | | | it was the consensus. |
| who, with the best will in the world, very often fall short | | | | With the coupling plates removed we were rapidly |
| on the promised deadline. | | | | closing on our target. Six nuts are all that now stand |
| Fortified with a strong cup of tea Patrick (the owner) | | | | between us and the completion of this part of the job. |
| and I set to work having removed all the side panels | | | | Surprisingly, they all come undone sweetly and with a |
| from around the engine. There is a nice bright cabin | | | | gentle lift and tug off its studs, the gearbox comes |
| type light installed in the engine room so at least light | | | | away from the bell housing and is laying on the cabin |
| will not be problem. First task is to drain the ATF | | | | floor. |
| (automatic transmission fluid) from the gearbox and | | | | Into a suitable sized bucket, lowering it carefully into the |
| this is done smoothly with the drain plug coming | | | | tender and rowing ashore is accomplished without |
| undone quite easily. Next, the gear cable is | | | | mishap. We shall have it on Barry the gearbox |
| disconnected from the gear lever and strung up out of | | | | engineers' workbench tomorrow morning sharpish, |
| the way. We remove the cable bracket as well as it | | | | leaving him to do the reconditioning which is a |
| will also be in the way when we come to wrestle the | | | | specialists' job. |
| gearbox off the bell housing of the engine. So far so | | | | |