Help: apparently I need a new gearbox shaft

[Marine89]

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.

[paintman]

What, if anything, have you noticed?
Could you fit a lower unit yourself?

[Marine89]

I hadn't noticed anything at all hence the surprise. Although if I think about it I do notice that after using the engine for a few hours when it is in low revs or idling I can hear a faint whistling sound...no idea if this is related. I only bought the boat a few weeks ago so not sure what noises are 'normal'.

Boatyard said there was some water in the gearbox oil.

My main concern is being ripped off as I'm a 26 year old girl as therefore probably an easy target!

[mick]

Sounds like there taking the pish I had the oil seals done in one of mine circa £300 and that was with other bits as well get a second opinion

[Max...]

You certainly need at least a second if not third opinion. I'm sure some locals will comment with recommended workshops to get it checked out.

[mick]

And look for second had if replacement needed

[Mollers]

Sounds outrageous! Get it out of there. It's a bit of a haul for you, but OSM at Lostwithiel are very professional and super fair. They'll only hit for what is necessary rather than piling it on. My Etec is with them for a service currently.

[beamishken]

I ran an 85 2 stroke for years with a bent propshaft & it never caused a problem I checked the oil colour regularly just in case a seal did fail as it is a possibility but mine never did I had the engine for about 5 years & it saw lots of use
If it's do slightly bent you can't feel it I'd keep an eye on the oil colour & just use it maybe look out for a good used box but I'd say sub £500 for a good used box isn't far away

[Marine89]

If I had hit something hard what would the likely damage be?

New prop shaft? New gearbox shaft? (is it the same thing?). Would I ever need a new gearbox shaft? Their answerphone message said it could have damaged the bearings and hence a new gearbox would be safer? Is this reasonable?

They have offered a whole new gearbox and shaft etc for £1750+vat+labour. Do I need to enquire about the origin of this second hand one?

Do you think the whistling might be related to this or not?

Thanks again so much for everyone's help- so much appreciated.

[Marine89]

If they say there's some water in the gearbox oil does this suggest it could be bad?

[paintman]

Agree with the above comments. A quick look on ebay shows one available for a lot less than they want. Just depends on what shaft yours is.
What a fantastic stroke of luck for you that they just happen to have a used gearbox in stock that they can do at a super price - how spooky is that (Or do I just have a nasty suspicious nature )
Changing a lower leg isn't difficult!
Long Shaft Gearbox Lower Unit ~ F80 F100 YAMAHA 80HP 100HP 4-Stroke Outboard | eBay

[Mollers]

Originally Posted by Marine89

If I had hit something hard what would the likely damage be?

New prop shaft? New gearbox shaft? (is it the same thing?). Would I ever need a new gearbox shaft? Their answerphone message said it could have damaged the bearings and hence a new gearbox would be safer? Is this reasonable?

They have offered a whole new gearbox and shaft etc for £1750+vat+labour. Do I need to enquire about the origin of this second hand one?

Do you think the whistling might be related to this or not?

Thanks again so much for everyone's help- so much appreciated.

If you can see no external damage, you're looking at a some internals at worst. No way should this come to £2k.

[Marine89]

Thanks paintman.

Would you be happy just doing the shaft rather than the whole gearbox as they think is necessary?

The fact that they happen to have the right second hand part is what made me slightly suspicious!

[paintman]

It's surprising how much impact a box can take without doing damage. Friend of mine trashed an alloy prop in a big way on a concrete lifeboat slip - I saw & heard it & was expecting a LOT of damage. Changed the prop & no subsequent issues at all. So I'd suggest it takes quite a lot to bend a shaft!
Difficult if you can't do your own work - I do. I'd drain the box oil & see what comes out. If there is water in it then there could be seal damage which may or may not be related to shaft issues. Could just as easily be a leaky drain/fill plug.
But if you've got no vibration issues throughout the rev range I'd renew the oil, run it & see what happens.
If you can't then I'd concur with getting a second opinion from somewhere recommended.

[paintman]

Bit about cavitation for you (lots on the net)
Boston Whaler | Propeller Cavitation, Causes and Corrections
"Propeller Cavitation, Causes and Corrections

Cavitation is a phenomenon that occurs in all propeller-driven craft under certain conditions. The surface of propeller blades is not perfectly flat, and as water is drawn through the blades to be discharged aft into the propeller's slip stream, the water flowing over the curved surface of the blade encounters areas of greater and less pressure. In those areas of reduced pressure, air bubbles are formed. When they move out of the low pressure area, these bubbles collapse. If they collapse while in contact with an object, such as part of the propeller blade or a trim plane, the bubbles create such highly localized forces that they erode the surface of the object. In the case of the propeller, such damage is sometimes called a "burn." It may be caused by an irregularity in the propeller's leading edge, and should be corrected by reconditioning the propeller or by replacement. Cavitation is a normal occurrence in modern boats and propeller inspection should be a part of routine maintenance."

[beamishken]

If someone is going to strip the gearbox to fit a new shaft they will have the bearings & gears out anyway so could all be checked at the same time
Sounds to me like they can't be arsed or aren't competent to repair your box so are taking the easy (& profitable) route of trying to sell you a box at an ott price
Personally I'd ask forum members to recommend a reputable trustworthy repairer in your area for a second opinion
Water in the oil is a sign of a seal leaking so possibly needs looking at but on the other hand it could be a sales ploy
I'd politely turn down the offer get the boat back & take it elsewhere

[Marine89]

Originally Posted by paintman

It's surprising how much impact a box can take without doing damage. Friend of mine trashed an alloy prop in a big way on a concrete lifeboat slip - I saw & heard it & was expecting a LOT of damage. Changed the prop & no subsequent issues at all. So I'd suggest it takes quite a lot to bend a shaft!
Difficult if you can't do your own work - I do. I'd drain the box oil & see what comes out. If there is water in it then there could be seal damage. But if you've got no vibration issues throughout the rev range I'd renew the oil, run it & see what happens.
If you can't then I'd concur with getting a second opinion from somewhere recommended.

Very help- thank you. If there is water in the gearbox oil, as they say, and therefore seal damage as you mention, can the seals just be redone rather than having a new gearbox?

They say there is vibration in the gearbox due to the bent shaft but I haven't noticed any vibration while running the boat. Would you keep running the boat?

Also so you think the whistling noise might be related?

Thanks again so much for your advice.

[Marine89]

Originally Posted by beamishken

If someone is going to strip the gearbox to fit a new shaft they will have the bearings & gears out anyway so could all be checked at the same time
Sounds to me like they can't be arsed or aren't competent to repair your box so are taking the easy (& profitable) route of trying to sell you a box at an ott price
Personally I'd ask forum members to recommend a reputable trustworthy repairer in your area for a second opinion
Water in the oil is a sign of a seal leaking so possibly needs looking at but on the other hand it could be a sales ploy
I'd politely turn down the offer get the boat back & take it elsewhere

Thanks for that. Any idea how much I should expect to pay (a) for the new shaft part and (b) how many hours labour to fit it?

[paintman]

Seals are a replaceable service item & I'd expect any other damage to be noted at the same time.
As I said, I'd renew the oil, run it & see what happens. With a view to draining & checking the new oil after a few hours. That is straightforward.
As you are having to rely on others I'd suggest collecting the boat, paying them for whatever it was you agreed to have done & then taking it to somewhere recommended.

[matt h]

Im sure there is a Ribnobber member that you could meet up with and check it out, sounds like a dealer rip off as pre mentioned!