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Old 07 September 2015, 02:34   #21
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Old 07 September 2015, 02:59   #22
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Are you Dartmouth way?
No, I am on the River Exe
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Old 07 September 2015, 03:10   #23
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Hi,
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.
they say the shaft is bent easy to check stand something at the side of one blade just touching and spin the prop note any gap or if they touch more on the other blades.
as said gear oil easy to look at if its milky its got water in it.
basically reading above they are scaring you into changing the lower unit.
props are not that expensive so don't worry about cavitation burns just make sure the prop has no bad nicks, if it has you can get it repaired for reasonable cost.
if it were me i would ring up barnet marine and cost the parts required to give you an idea any good car mechanic would be able to change the parts for you just download a service manual and follow.
and get your boat away from these guys if it went in for an unrelated problem why are they looking at your gearbox [to make money out of the vulnerable] and possibly wont stop there.
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Old 07 September 2015, 04:36   #24
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Hi Marine89,

PM me your details. I'm sure I'll be able to help you out.

Cheers.

Dan
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Old 07 September 2015, 05:05   #25
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I think there be assumption that the shaft is actually bent.
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Old 07 September 2015, 05:18   #26
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If you hit something and damaged it - would it be insured ?
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Old 07 September 2015, 23:24   #27
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they say the shaft is bent easy to check stand something at the side of one blade just touching and spin the prop note any gap or if they touch more on the other blades.
Are we talking about the prop shaft or the drive shaft (head to LU)?

Prop shaft is easy to check: remove prop, run motor on muffs, and place in gear at idle. any untrue condition will be pretty obvious. Jeff's method may show a problem with the shaft when it is actually the prop.

I suppose you could do the same with the driveshaft, after removing the LU (though you'd have to have it in gear and spin the prop by hand.)

jky
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Old 08 September 2015, 03:40   #28
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Is it only me thinking that if the OP had hit something hard enough to bend the prop shaft, that there'd be obvious damage to prop/skeg/gearcase. If non-of this is evident..........
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Old 08 September 2015, 04:13   #29
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Is it only me thinking that if the OP had hit something hard enough to bend the prop shaft, that there'd be obvious damage to prop/skeg/gearcase. If non-of this is evident..........
you're right Dave i assumed this had happened before the present owner got the boat as prop damage/skeg/gearbox not mentioned to be honest if the shaft is bent just spinning the prop by hand out of gear shows just by looking at the hub.
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Old 08 September 2015, 04:19   #30
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you're right Dave i assumed this had happened before the present owner got the boat as prop damage/skeg/gearbox not mentioned to be honest if the shaft is bent just spinning the prop by hand out of gear shows just by looking at the hub.
In which case, if it's historical damage, I'd run it as it is. L.I.D
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