water in gearbox Yamaha 4hp 1994

[Abraham62]

Hello,have some water in my gearbox oil.Try to pressure test the gearbox to find out where there might be. a leak, but air is directly flowing through the rubber of the shift lever.Cannot imagine that this is the problem, or am I wrong ?.

Secondly,would it be a problem to have 'milky oil' but then change it now and then ?

Regards,

Abraham

[fairdeal]

I'm puzzled why you wouldn't imagine,
that a hole in the shift rod boot,
is where the water is getting into the gearbox?

its only purpose is to keep oil in, and water out

https://www.boats.net/product/yamaha/6G1-44147-00-00?q_ref=6G1-44147-00-00

[Abraham62]

[Abraham62]

If I put compressed air into the oil refill plug,the air is flowing out through the black rubber where the shift lever is entering the gearbox,guess this is normal,or ?.I have 'milky oil' in the gearbox and tried to find the cause of water entering

[TownsendsFJR1300]

If I put compressed air into the oil refill plug,the air is flowing out through the black rubber where the shift lever is entering the gearbox,guess this is normal,or ?. NO, IT IS NOT. I have 'milky oil' in the gearbox and tried to find the cause of water entering

You might want to read post #2 again.

We assume all the oil is out of the unit when pressurizing.

There are many seals in the unit: https://www.boats.net/catalog/yamaha...casing-drive-1 but as noted, no air should be coming out anywhere (with the correct air pressure).

And, it's not good to run water mixed with oil in the LU. Kinda defeats the purpose of having 90wt oil in there..

Seals are a lot cheaper than bearings, shafts AND seals.

[99yam40]

what pressure are you putting into the box?
if too much it could push a seal out of place

[Abraham62]

Hello,I am putting only a little bit of air into the lower unit.The shift rod boot is almost immediately expanding,like a small balloon,and air is released at top of the boot.I have replaced the lever and boot with an old spare that I had.Same issue Secondly,when looking at this boot,or on the drawings,I do not see an integrated oilseal that would withstand some little pressure.So I am still puzzled on the function of this boot.Given the minor costs of this item might take it to the shop and ask them for some advice, and/or buy a new one

[TownsendsFJR1300]

Looking at the picture of the new boot, the base obviously slips into the LU snuggly(thick base, with "grooves"). The top has a spring to keep tension around the top.

Being your engine is TWENTY FIVE YEARS OLD, I wouldn't expect that rubber to last that long. Could be a hairline crack, just old age / worn.. That shaft does NOT spin (like most other shafts in the LU), just up and down, an accordion.

Depending on IF you over pressurized, you know that boot is leaking. Putting another old, rubber hardened up "seal" is NOT the way to go...

Asked but not answered, how much PSI are you pumping in the LU?? You may very well have other leaks elsewhere.

[99yam40]

being that I and probably most others on this board do not have a service manual for that 4hp Yamaha, we have no idea what pressure if any you should be putting on the gear case.

might try to find a service manual so you can read it

[zenoahphobic]

If the "bellows" expands before air escapes at the top means the pressure has exceeded that spring pressure.
I don't think there will be a spec on what that pressure would be as it is a simple seal.
If this cannot be replaced, it simply can be sealed with the appropriate silicon (silkiflex?) and a suitable clamp replacing the spring, because this part is fixed and moves with shaft. The bellows will take up the pressure changes that maybe encountered.
But I would not discount this rubber tube and the other seals are due for replacement. With this overhaul you will encounter grooves or wear on the shafts that may be a challenge to "smooth out" to provide an adequate seal with new seals.
You may need to do this extra improvisation as who is to say the shop spare part provided is not also the same age as the engine!

[Abraham62]

Soem new info,went to shop,i have put indeed to much air in it,hopefully have not damaged anything....I had some spare time and removed the gearbox/propeller shaft and am now thinking of replacing the oilseas there as there were some traces of fishing lines etc,should not be to difficult ?

[TownsendsFJR1300]

If there's still line in there, I'd remove it and re-check if it seals.

I would also re-pressurize to know EXACTLY where your leak is.

You can always re-seal the entire unit due to it's age and you may have issues removing the lower prop shaft carrier.

Salt water, aluminum and time like to bind them together

[panasonic]

Soem new info,went to shop,i have put indeed to much air in it,hopefully have not damaged anything....I had some spare time and removed the gearbox/propeller shaft and am now thinking of replacing the oilseas there as there were some traces of fishing lines etc,should not be to difficult ?

Abraham62 what is the exact model and serial number of your engine? I have shop manual for a 1995 4 hp.

The lower units appear to the same part number from 94 to 95. I can send you the info on how to change required parts to reseal your lower unit.

Pressure test is 14 psi for 10 seconds.

1995 4 pressure.JPG