Milky gear oil

[Tommy c]

I don't know when it was last changed so could be quite old but is it acceptable to have milky gear oil or no matter how old the oil is, should it still be its normal colour.

[TmMorris]

It's got water in and has emulsified. It stops being an effective lubricant at this point.

You just need to find which seal needs replacing, sometimes just doing the lot makes the most sense.

[babbot1]

That sucks. Been there a couple times.
First check the drain and fill plugs. Matting surfaces need to be clean and use new washers. Then check the prop seal doesn't have fishing line around it.
If this is a big motor maybe send the lower unit out to pressure test it.

[Tommy c]

So it's definitely a seal needs replacing??
The engine is a yam 5hp 2 smoke.
The gear selector is just a push rod through a rubber boot. I thought these might not be 100% water tight.
The amount of oil drained is no more than what is required to fill and no separate water came out.
Are the seals a pig or fairly straightforward to replace

[babbot1]

Marine gear oil will actually mix with the water to give you what you have.
It is most likely a seal somewhere. You can send it out for a pressure test or if you are ambitious you can make one yourself with a little google searching and a bike air pump.
I rather do the work in testing it than throwing parts at it until you find it. It's actually going to be hard to validate which seal it is without a pressure test.

[jeffstevens763@g]

I would take the top level plug out and pressurise with a bike pump and see where the oil seeps out

[Matt]

I made up a pressure test kit out of a cooling system pressure tester I already had, an adaptor for the tester, plus the adaptor you get to refill the gearcase with oil.

Overkill for what you have here, but pic just to give you the idea.

If the gearbox is anything like my Johnson 5 2 stroke, they're not hard to rebuild, but are a bit fiddly. Hardest bit is usually getting the waterpump assembly off - the bolts often shear, as per other thread on here.

[beamishken]

Originally Posted by Tommy c

So it's definitely a seal needs replacing??
The engine is a yam 5hp 2 smoke.
The gear selector is just a push rod through a rubber boot. I thought these might not be 100% water tight.
The amount of oil drained is no more than what is required to fill and no separate water came out.
Are the seals a pig or fairly straightforward to replace

The Achilles heel of those engines is corrosion below the waterpump where the shaft seals fit. Pull the pump & take a look, if the seal seats arent rotted away your a very lucky guy
Pressure test doesnt always tell the whole story, theres two seals on each shaft one to keep oil in the other to keep water out you occasionally get one gone without the other & allows water in but not oil out or vice versa. For what they are on a 5 its worth changing them all

Sent from my SM-G950F using RIB Net mobile app

[Matt]

Yeah, on both my 5 Johnson and 2 Yamaha I actually ended up buying complete replacement cases off eBay due to corrosion and just reused some of the internals.

[Tommy c]

Originally Posted by beamishken

The Achilles heel of those engines is corrosion below the waterpump where the shaft seals fit. Pull the pump & take a look, if the seal seats arent rotted away your a very lucky guy
Pressure test doesnt always tell the whole story, theres two seals on each shaft one to keep oil in the other to keep water out you occasionally get one gone without the other & allows water in but not oil out or vice versa. For what they are on a 5 its worth changing them all

Sent from my SM-G950F using RIB Net mobile app

Yeah I have no problems replacing all the seals. For a pair of upper, a pair of lower and a lower and upper water pump housing gasket it's all under £40.
I can't help thinking that the gear selector rod is a weak spot. It just pushes in and just has a rubber boot were it goes through the lower housing plate.
Probably highlights the importance of upper and lower impeller housing gaskets replacement when changing the impeller instead of just the impeller itself.
Any tips or pitfalls to be aware of whilst changing the oil seals?
Thanks

[Matt]

Just be patient taking it apart - they're quite thin castings. Waterpump bolts quite likely to shear off - so be prepared for that. It's quite enjoyable - they're a proper little gearbox with dog clutch etc in so it's interesting to see how it all works.

[Tommy c]

Originally Posted by Matt

Just be patient taking it apart - they're quite thin castings. Waterpump bolts quite likely to shear off - so be prepared for that. It's quite enjoyable - they're a proper little gearbox with dog clutch etc in so it's interesting to see how it all works.

Haha, see my earlier thread re snapped bolts.

[Matt]

I apologise - I even commented on the thread, but didn't pay attention to the fact it was you.

[TmMorris]

Originally Posted by Tommy c

So it's definitely a seal needs replacing??
The engine is a yam 5hp 2 smoke.
The gear selector is just a push rod through a rubber boot. I thought these might not be 100% water tight.
The amount of oil drained is no more than what is required to fill and no separate water came out.
Are the seals a pig or fairly straightforward to replace

Easy to be honest.

You'll have a pair of bearing seals around the shaft up the engine, under the water pump plate. Another pair of the same type in the prop shaft bearing. They need to be fitted the right way round as per the parts diagram.

The seal to the gearbox housing with the prop shaft housing is a large o ring but leaks there are a bit unusual but over time the two surfaces can oxidise and need a bit of emery to return to good form.

The gear leave has a rubber boot that is held against the gear stick with a retaining spring type washer and goes down to a nylon cam shaped piece that serves as the main seal. These are also unlikely to be the issue unless someone has failed to replace the nylon egg in the right position and the screw that exists to splay it out to form the seal isn't tight or able to do its job.

You can buy all of these bits from someone like BHG Marine and they're easy to fit.

It doesn't take much water to emulsify the oil but you do want to try and locate the point of ingress as you replace the seals, it usually obvious and if I had to rank the suspects then I'd start with the pair of bearing seals in the prop shaft, then the pair under the impeller. I think for the others to be candidates it would generally require a previous owner to have botched a rebuild etc.

[Matt]

Yeah, I used BHG for my yammie. Their service was good.

[beamishken]

Originally Posted by Tommy c

Haha, see my earlier thread re snapped bolts.

I just looked at your pictures on your other thread too , you are indeed a lucky bloke that box looks mint in comparison to many you see, the attached pictures are just a couple I have lying about but probably more typical than yours for corrosion

[Matt]

Yeah, when I did the lower on my 2hp, it looked quite a bit like your right hand pic. So new casting from ebay.....

[Limecc]

Originally Posted by Matt

Yeah, when I did the lower on my 2hp, it looked quite a bit like your right hand pic. So new casting from ebay.....

It's a worry, is there nothing preventative to be done?

[Matt]

I suspect my 2hp motor had never been flushed, nor had the anode changed, prior to me owning it.

[Limecc]

Originally Posted by Matt

I suspect my 2hp motor had never been flushed, nor had the anode changed, prior to me owning it.

My 50hp has always been flushed yet still had a bit of crumbling alloy and corrosion going on. Makes me wonder if it's electrolytic and an anode would help.