A friend has had an issue with a VP MSA4 gearbox that has one broken gear. Apart from the break, there doesn't look to be excessive wear, so i wonder what might have caused the problem. I do have a suspicion, has anyone seen something similar ?
Having had issues with a MS4B a few years ago would recommend going down the repair route before considering anything else and and would suggest you take up any offer regards a gearset , few parts are still available new from VP for this reverse gear but the gear set is long long out of production.
The box is fairly basic and a simple job to rebuild if you can persuade somebody to rebuild it !
Despite its reputation, there must have been 10 of thousands of these things installed and suspect the vast majority are still in use.
Finding a replacement reverse gear is not difficult, however fitting is.
The engine mountings will need to be moved back on their beds and the output shaft angle is different , so engine down angle also will need to be adjusted to line up with the output shaft flange angle .
Water cooling modified and gear linkage altered.
Check which ratio your existing gearbox has, the two most popular were 1.98 :1 and 2.63 :1 there was also one other.
Possible replacement boxes appear to all have slightly different ratios from the MS4 and you may need to consider altering your prop pitch to compensate. Volvo Penta MSB4 Gearbox Issue - Cruisers & Sailing Forums
Ps. Secondhand MS4 gearboxes are much rarer than hens teeth, new examples do surface ie. one on ebay for around $4000.00 and you have got to ship and pay customs duties on top.
This was probably the result of hitting the bottom. It took a few weeks before it actually failed.
Thanks everyone for the replies. The gearbox has already been rebuilt, i was really just looking for opinions as to why the gear has broken. The gearbox people said it was just wear, but it doesn't look worn on the other teeth. I wondered if it might have been caused by picking a line up on the prop.
Needs a real shock to do that ?
Did help somebody else to sort another drive shaft breaking in exactly the same place as mine, although in his case the break was compound .
In both cases we were able to buy new shafts from VP and with expedited delivery they were delivered within 48 hours and were back in the boats a day later.
One boat was P35, the other a Fairline Corniche 31 of similar vintage.
He always steadfastly claimed he never hit anything.