Gearbox Leak Test

[Willdoe]

Am getting a bit of watercontamination in the gearbox oil on my 2004 30hp 2stroke Yammy. Heard you can locate the source by draining the oil and pressurising the case under water and look for bubbles.
Questions:
1. Does this work and what pressure should I use?
2. Can the prop shaft seals be pulled while the carrier is in the box? If so how/ what tools?

Willdoe

[Moonlighter]

There are 3 usual suspects for water in gearbox oil:

1. Prop shaft seal. Usually a visual check will reveal damage and oil leaking.

2. Top filler screw seal

3. Bottom oil plug seal..

Both of these plugs have usually a nylon washer that must be replaced every time the gearbox oil is replaced. I once had my motor serviced and they found that one of these seals had been left off the time before! Luckily no water had got in, although we don't know why.

Check these 3 things first and you will most likely find the cause.

Cheers

ML

[cormorant]

You do both vacume and pressure test at low pressure and do so after putting in new seals. They are cheap . Add to the above list the driveshaft seal as well and the bearing carier seal. Propshaft is the regular offender as it gets fishing line around it . Do the obvious and check your shafts and prop are running true and there is no slop. Using a propper marine water resistant gearbox oil helps save a lot of damage as well.

[Spaniard_King]

There are 3 usual suspects for water in gearbox oil:

1. Prop shaft seal. Usually a visual check will reveal damage and oil leaking.

2. Top filler screw seal

3. Bottom oil plug seal..

Both of these plugs have usually a nylon washer that must be replaced every time the gearbox oil is replaced. I once had my motor serviced and they found that one of these seals had been left off the time before! Luckily no water had got in, although we don't know why.

Check these 3 things first and you will most likely find the cause.

Cheers

ML

Not for this gearbox! The shift rod boot is the main culprit and will take no more than 2-3psi to blow the boot seal out. If its the late model (post 2008) then possibly the o-ring on the housing beneath the water pump (strange shapped o-ring that does not seal well) Either wway don't put more than 2-3psi into these boxes

[Willdoe]

Thanks for replies The motor is a 2 cylinder HMH model, 2003 not 2004 as I initially quoted . I currently have the box off the motor. I dont want to replace seals unnecessarily and create maintenance induced failures. So the process is??
Willdoe

[Willdoe]

The gearcase on this site is the same as mine.
http://www.boats.net/parts/search/Ya...201/parts.html

Spaniard King is part No20 the seal you would replace. Its an O ring not a boot as you mentioned or were you thinking of a different gearcase.

[Spaniard_King]

Item # 26 is the one I had to replace, you can put 10psi in that box to check for leaks