outboard gearbox not venting

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Two Sheds

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Hi all

Problem servicing my Mercury 3.3 outboard. The gearbox oil drained out fine, but when refilling (from the bottom hole) it doesn't seem that the top hole is actually venting. No oil comes out mo matter how long I squeeze the tube for, and if I subject the tube to extreme pressure, squeezing it in G cramps, the pressure is such that the oil is forced back past the nozzle. (spectacularly so, I just finished cleaning up the garage...).

Has anyone come across this before?

Thanks
Martin
 
martinbazen said:
Hi all

Problem servicing my Mercury 3.3 outboard. The gearbox oil drained out fine, but when refilling (from the bottom hole) it doesn't seem that the top hole is actually venting. No oil comes out mo matter how long I squeeze the tube for, and if I subject the tube to extreme pressure, squeezing it in G cramps, the pressure is such that the oil is forced back past the nozzle. (spectacularly so, I just finished cleaning up the garage...).

Has anyone come across this before?

Thanks
Martin
Click to expand...
fill from the bottom hole with the nozzle provided with the squeeze bottle & use the top hole to vent.
when oil flows out insert the bottom bung
 
martinbazen said:
Hi all

Problem servicing my Mercury 3.3 outboard. The gearbox oil drained out fine, but when refilling (from the bottom hole) it doesn't seem that the top hole is actually venting. No oil comes out mo matter how long I squeeze the tube for, and if I subject the tube to extreme pressure, squeezing it in G cramps, the pressure is such that the oil is forced back past the nozzle. (spectacularly so, I just finished cleaning up the garage...).

Has anyone come across this before?

Thanks
Martin
Click to expand...

Tried warming the whole thing a bit.

Tried putting some pressure on the top hole to see if you can blow an obstruction clear ?
 
sailorman said:
fill from the bottom hole with the nozzle provided with the squeeze bottle & use the top hole to vent.
when oil flows out insert the bottom bung
Click to expand...

That's exactly what I've been doing, only the oil doesn't flow out! (and in fact I understand that when the oil flows out you insert the top bung first so that the vacuum holds the oil in while you replace the bottom one. I also had the oil good and warm first, but it made no difference. I'm going to try turning the propeller as suggested by BarryH.

Thanks all
Martin
 
I've never really understood the logic of filling from the bottom. I always put the bottom bung in, lay the engine on its side and dribble the oil into the top hole, turning the prop occasionally. Stand the engine up and put the top bung in when the oil stops dribbling out.
 
alahol2 said:
I've never really understood the logic of filling from the bottom. I always put the bottom bung in, lay the engine on its side and dribble the oil into the top hole, turning the prop occasionally. Stand the engine up and put the top bung in when the oil stops dribbling out.
Click to expand...

Its done so that there is no possibility of trapping air pockets resulting in an incomplete fill.
It is also easier if the oil goes in one hole and the air comes out of the other. With viscous oil and pretty a small hole it can be pretty messy trying to get oil in and air out through the same hole at the same time.

You do need a squeezy bottle with a tapered nozzle that screws tightly into the filling hole to do it, or better still the proper filling pump accessory that screws into the filling hole of your brand of outboard.

Having said that I do sometimes use the brass syringe shown below but as it only holds about 75cm³ it requires several syringe full to refill the gearcase. On balance probably no easier than filling from the bottom with the added risk of perhaps not getting the unit properly filled.

DSCF0863.jpg
 
Well, I've made another sticky mess in the garage! Oil well warmed, and turning the propeller ( both in and out of gear) made no difference at all. The pressure builds up, and the oil eventually comes back past the filler nozzle. Very little is getting in there, and it just seems to me that the vent isn't venting. Once it has drained clean, I'll try putting air pressure in, to see if it vents (either way). Thanks for all the help.

Martin
 
martinbazen said:
Well, I've made another sticky mess in the garage! Oil well warmed, and turning the propeller ( both in and out of gear) made no difference at all. The pressure builds up, and the oil eventually comes back past the filler nozzle. Very little is getting in there, and it just seems to me that the vent isn't venting. Once it has drained clean, I'll try putting air pressure in, to see if it vents (either way). Thanks for all the help.

Martin
Click to expand...

I was just going to ask the same question as misterg.

The two plugs are identical .. I cannot see anything that you'd remove by mistake anyway.
 
Completely sure I've got the right plugs, as per the manual.

But things are going from bad to worse. I used the dinghy pump to put air pressure in, and there is clearly a total blockage, as air pumped into either orifice does not come out of the other.

So, I decided to take the gear housing off to investigate.

So, naturally, both of the bolts retaining the gear housing have sheared off.

And, equally naturally, the gear housing is seized on solid and won't come off, even with the bolt heads off. I've tried heating it, and the application of wooden mallet, but no dice.

Any suggestions welcome but I'm starting to think about taking it somewhere to get it fixed.

Cheers
Martin

PS. I've had enough of boats today; I'm going to go and tinker with my motorbike.
 
martinbazen said:
Completely sure I've got the right plugs, as per the manual.

But things are going from bad to worse. I used the dinghy pump to put air pressure in, and there is clearly a total blockage, as air pumped into either orifice does not come out of the other.

So, I decided to take the gear housing off to investigate.

So, naturally, both of the bolts retaining the gear housing have sheared off.

And, equally naturally, the gear housing is seized on solid and won't come off, even with the bolt heads off. I've tried heating it, and the application of wooden mallet, but no dice.

Any suggestions welcome but I'm starting to think about taking it somewhere to get it fixed.

Cheers
Martin

PS. I've had enough of boats today; I'm going to go and tinker with my motorbike.
Click to expand...

I guess the gearcase is now held by corrosion products around the remains of the two bolts !

To remove it you do also have to disconnect the two halves of the shift rod at the joint accessible by removing the rubber plug on the side of the leg above the leg to gearcase joint.
The drive shaft also has to pull from the crankshaft. If that was not greased lightly when last refitted it could well be rusted in.
 
Thanks Vic. Mine didn't have a rubber plug (that could explain a lot!) and I have loosened the bolt on the shaft, which is now loose. Suspect you are right about the corrosion. I'll have a bit of a think about it all (and fix my motorbike) before further steps.

Thanks all for your help.
Martin
 
VicS said:
You mean the plug was missing?

It should not cause any problems, apart from exhaust noise.
Click to expand...

Yes, the plug was missing. Not sure if its function is to keep water out or not, but it wasn't there anyway.

Next step will be to soak the corroded and snapped off bolts in ACF 50, also the joint. I've not come across Bert's Kano Kroil, but ACF 50 is very good, although expensive.

Thanks
Martin
 
martinbazen said:
Yes, the plug was missing. Not sure if its function is to keep water out or not, but it wasn't there anyway.

Next step will be to soak the corroded and snapped off bolts in ACF 50, also the joint. I've not come across Bert's Kano Kroil, but ACF 50 is very good, although expensive.

Thanks
Martin
Click to expand...

Not used ACF 50 is it a good penetrating oil ? The website seems to suggest it is is mainly an anti-corrosion fluid.

The best readily available penetrating oil that I know of is PlusGas.

Top of the list in the USA seems to be PB Blaster
 
VicS said:
Not used ACF 50 is it a good penetrating oil ? The website seems to suggest it is is mainly an anti-corrosion fluid.

The best readily available penetrating oil that I know of is PlusGas.

Top of the list in the USA seems to be PB Blaster
Click to expand...

A very good point, Vic, thanks for that. I will try to get some PlusGas on it. Incidentally, I read somewhere that the best penetrating oil is a 50:50 mix of ATF and acetone, but haven't tried it myself.

Martin
 
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