my motor sailor is fitted with a bmc 2.2 commander engine and i have been told it has a bmc manual gearbox which needs adjusting as it slips into gear and will not stay in neutral. Is this a simple job to do and how do i go about it ?
The gearbox is, I suspect, made by Parsons or by Newage under licence from Parsons. I used to have one of these, but never had this particular problem. Most gearboxes have a spring-loaded ball detent to lock the box into the gear position, but I cannot recall where this might be on that gearbox. The problem may be caused by a broken spring in this detent. I would start by removing the cover on the top of the box and looking inside. If nothing is obviously visible, it may require the removal and dismantling of the box. The detent mechanism will be on the gearlever shaft or the long rod which runs forward from the shaft to the conical clutch. As it usually takes a fair bit of effort to get the box into gear, inspect the linkage outside the box to see if anything is bearing upon it to push the gearlever into the 'in-gear' position.
On these boxes when you take the cover off you will see three dogs ( you will have to turn the inners to see all three ) which slip over the cone on each of these dogs there is a adjustment bolt with a lock nut.
I would tighten these about half a turn each equally and lock the bolts off again, this should fix your problem !
If you overtighten you will not be able to get it into forward gear, also if to much adjustment the gearbox will slowly creep !