Help: apparently I need a new gearbox shaft
I took my 5.4m Rib with 80hp Yamaha 4 stroke into a boatyard for an unrelated reason and was told that I must have hit something and needed a new gearbox shaft and seals. The only time I remember hitting something was going about 4 knots and hitting the mud so was surprised there was such damage.
I was quoted over £2000 +vat + labour for a new gearbox which was a bit of a shock. They said it was a risk just changing the shaft and I would be better with a new gearbox. Does this sound right? Would it be too risky just to change the shaft? Any idea how much this might cost? They also said they had an outboard for spares and could sell me a whole gearbox for £1750 +vat + labour instead.
I'm afraid this is an area I know nothing about so would be really grateful for any help about whether this price seems right, or if there's any way I could get this done cheaper. I am worried I am being ripped off here!
To be more specific, I wrote down the following about what they told me:
At some time the prop has hit something. This has resulted in a bent gearbox shaft. As the shaft is slightly bent there is vibration in the gearbox. Which in all probability will lead to water getting past the rubber seals and getting into the gearbox oil. Another problem caused by the vibrations in the shaft is that the prop is becoming damaged by cavitation there is evidence of this but so far the damage is only slight. However in time the prop blades could be badly damaged. In the short term the engine could still be used although the gearbox oil should be changed. However in the long term either a new gearbox shaft and seals would have to be fitted or a totally new gearbox would be needed. The boatyard. have an almost new second hand gearbox off another engine available and fitting this might be more economical than putting a new shaft in the existing gearbox.