Outboard Gearbox Failure - could motor sailing be a factor?

[Arida]

I don't want to gain a reputation for idiot posts and therefore I post this with some trepidation. However, as a novice sailor, helpful advice would be appreciated.

This morning we set off from Birdham Pool against the incoming tide, the plan being to sail to Chichester harbour mouth and then up the Emsworth channel to our mooring near Emsworth.

Quite heavy going through Itchenor, maybe 2-2.5 knots at 3/4 revs. Decided to raise the sails (both main and genoa) to help. This had limted effect at first as we were sailing almost directly into the wind and the opportunity for tacking was limited.

As the channel widened we were able to tack some more and increase speed somewhat. This, the approach of high tide and the stronger wind near the harbour mouth meant that by the time we passed the Thorney Island channel we were doing maybe 4 knots with a combination of sail/motor. Great.

Then suddenly the outboard pitch increased as if it had lost its load. My immediate thought was that we had shed the prop or the hub adhesive had failed. I won't go into detail on the next bit, but suffice to say we ended up in Sparkes marina and I removed the outboard from the boat.

Testing at home I found that the prop hub was ok, but that turning the prop by hand caused a graunching sound somewhere near the bottom of the outboard leg. This happened in both forward and reverse gears, but not in neutral. It seemed like the output shaft within the gearbox was sometimes meshing and sometimes slipping.

Conclusion would appear to be gearbox failure. My question is could this have been caused/contributed to by "agressive motor sailing" or is it more likely due to sustained operation under load on an old/possibly poorly maintained outboard (I only aquired this season and understood it had been recently serviced, but "recent" and "service" are both relative concepts really, unless one has actualy done it oneself).

Thoughts appreciated?

(Kingfisher 20, 1990s Mariner 5HP 2st long shaft outboard in well. Yamaha based engine.)

Thanks,

Rob

 

[VicS]

Id not think motor sailing would cause any problems.

Obviously something failed in gearbox or possibly the vertical driveshaft broken.
You are going to have to strip it down so pointless speculating what might have failed,

It'll be interesting to know the overall condition inside. It may have been operated with water in the box if not serviced and the oil changed regularly.

A lot (most) of the parts are obsolete You'll be lucky if you can repair it.

http://www.boats.net/parts/search/Merc2/Mariner/5C/6E3-102151 AND UP/GEARHOUSING ASSEMBLY/parts.html

Bill Higham perhaps for parts or complete box.

 

[Arida]

Gulp

Id not think motor sailing would cause any problems.

Obviously something failed in gearbox or possibly the vertical driveshaft broken.
You are going to have to strip it down so pointless speculating what might have failed,

It'll be interesting to know the overall condition inside. It may have been operated with water in the box if not serviced and the oil changed regularly.

A lot (most) of the parts are obsolete You'll be lucky if you can repair it.

http://www.boats.net/parts/search/Merc2/Mariner/5C/6E3-102151 AND UP/GEARHOUSING ASSEMBLY/parts.html

Bill Higham perhaps for parts or complete box.

Thanks Vics. Engine was running very well prior to failure (easy start, fairly smooth running, stable revs, good telltake, low smoke) so I would be surprised if it was too neglected. But as you say it will be interesting to find out....

Regards,

Rob

 

[david_bagshaw]

If you are lucky perhaps the selector system has come loose.

check the pivot points under the cowl and the grippy joint that is under a rubber bung usually half way down the leg.


The sailing & motoring wont be cause of failure. more likely to help extend life as there is less load on the engine for a given speed.

 

[VicS]

Gear selector is something worth checking

Upper parts in in this diagram http://www.boats.net/parts/search/Merc2/Mariner/5C/6E3-102151 AND UP/GEAR SHIFT LINKAGE/parts.html

Lower parts in the link given earlier.

The clamp joint between the upper and lower parts of the shift rod being accessible as David Bagshaw says via the rubber plug in the side of the drive-shaft housing and unfortunately about all that is accessible without removing the power head to get at the bits at the top or dismantling the gearcase to get at the bits at the bottom.

 

[Arida]

Oh well....

David/Vics,

Thank you for your thoughts on the gar selector - unfortunately it turned out to be all ok, at least up to the point where it entered the lower unit.

I drained the grease from the lower unit. It was a bit milky in appearance, but still felt very much like grease and not much like water. It did however feel a bit "gritty", which I guess is likely be metal fragments. Also an intense smell, a bit like butane gas. Odd.

Definately no rotation transferred from drive shaft to prop or vice versa, irrespective of gear selector position, so fault is certainly in lower unit. Given the lack of spares availability, I am not sure there is much to be gained in dissasembling the lower unit further.

Perhaps time to hit ebay, either to find a replacement lower unit or, perhaps more realistically, someone who wants to buy a good power head....

Regards,

Rob

 

[Topcat47]

Motorsailing actually reduces the load on the outboard. For a given throttle opening the engine speed increases as does the internal friction leaving a lower load to be transmitted to the prop. As long as there's adequate lubrication in the gearbox, this isn't going to cause failure.

If there's existing bearing or gear wear, failure may be induced by the prolonged use of the engine, but you'd feel the increased vibration in the unit long before failure.

Are you sure you've not broken the shear pin? In my experience this is the first thing to go in the drive train.

 

[VicS]

David/Vics,

Thank you for your thoughts on the gar selector - unfortunately it turned out to be all ok, at least up to the point where it entered the lower unit.

I drained the grease from the lower unit. It was a bit milky in appearance, but still felt very much like grease and not much like water. It did however feel a bit "gritty", which I guess is likely be metal fragments. Also an intense smell, a bit like butane gas. Odd.

Definately no rotation transferred from drive shaft to prop or vice versa, irrespective of gear selector position, so fault is certainly in lower unit. Given the lack of spares availability, I am not sure there is much to be gained in dissasembling the lower unit further.

Perhaps time to hit ebay, either to find a replacement lower unit or, perhaps more realistically, someone who wants to buy a good power head....

Regards,

Rob

Gotta strip it down in order to tell us what is wrong.

 

[penfold]

If the selector mechanism has come loose the dog clutch may have been in partial engagement causing the grinding noise and creating the metal fragments. Depending on how much damage there is to the dogs it may be re-usable.

 

[Arida]

Motorsailing actually reduces the load on the outboard. For a given throttle opening the engine speed increases as does the internal friction leaving a lower load to be transmitted to the prop. As long as there's adequate lubrication in the gearbox, this isn't going to cause failure.

If there's existing bearing or gear wear, failure may be induced by the prolonged use of the engine, but you'd feel the increased vibration in the unit long before failure.

Are you sure you've not broken the shear pin? In my experience this is the first thing to go in the drive train.

Sadly not - this engine uses a spline drive rather than a shear pin (and no the hub adhesive has not given way either) 8-(

 

[Arida]

Post Mortem.

Gotta strip it down in order to tell us what is wrong.

Ok, ok. But probably have to wait until the weekend. Some of us don't have dedicated workshops....

 

[misterg]

I drained the grease from the lower unit. It was a bit milky in appearance, but still felt very much like grease and not much like water. It did however feel a bit "gritty", which I guess is likely be metal fragments. Also an intense smell, a bit like butane gas. Odd.

It should be oil AFAIK. Sounds like the box has been leaking and the oil has emulsified (and hence box has failed).

I would have expected the g'box oil to have been changed as part of a "service".

The additives in gearbox oil tend to make it smell sulphurous, which might be where the whiff is coming from.

Andy

 

[david_bagshaw]

Ok, ok. But probably have to wait until the weekend. Some of us don't have dedicated workshops....

as vic says gotta strip it down.

the butane smell is the gear oil, being hypoid, same as in a car diff. the fact you refer to it as a type of grease tells me there has been water there for a while, however the gunge might be preventing proper engagement.

Another reason to strip

 

[Arida]

Fallen at the first hurdle

as vic says gotta strip it down.

the butane smell is the gear oil, being hypoid, same as in a car diff. the fact you refer to it as a type of grease tells me there has been water there for a while, however the gunge might be preventing proper engagement.

Another reason to strip

Cannot get the gear housing cap off (item 44 in Vics first figure). Removed the bolts and tried to split it from the gear housing using an old screwdriver as a drift, but it seems to be seized solid - tapping with a hammer just digs into the ali and if I hit any harder I reckon I will crack the casting. What is the secret method please?

Got in the other way ok - removing water pump at the top - drive shaft end looks fine and drive shaft turns very smoothly in its bearing. Can obviously see the inside of the pinion through the drive shaft hole, but not the teeth on the outside of it, nor the gears on the prop shaft, so not much help....

Regards,

Rob

 

[Niander]

Tell us when did you last change or check the oil in the gearbox?

answer honestly please...
first thing i EVER do when i get a new [old] outboard[normally seagulls]
is check the oil in the gearbox and actually seagulls have excellently hardened gears

 

[Arida]

Tell us when did you last change or check the oil in the gearbox?

answer honestly please...
first thing i EVER do when i get a new [old] outboard[normally seagulls]
is check the oil in the gearbox and actually seagulls have excellently hardened gears

I plead the fifth ammendment....