Gearbox woes; unexplained oil leak

[FarOutFlores]

We run three F200B's (one of them is an FL200B) on our boat. Having heard a knocking sound on a recent trip, we opened the gearbox revealing huge damage to the forward gear and pinion. After replacing those gears, reassembling and then doing the first gear oil change early, the same engine had the same knocking; this time the reverse gear was damaged!
Mechanic said the oil was extremely low when he drained it. No idea where it's leaking from.
Any suggestions..?

[ausnoelm]

As a general rule, water leaks into the gearbox, rather than oil leaking out! Mind you, anything is possible, is there a chance you didn't refill ot properly when you did the rebuild?

[TownsendsFJR1300]

If he pressure tested it after the first re-build, it should have shown ANY LEAKAGE.


Second time failure- It would have been nice, once he drained the oil initially, noticed it low, to do that pressure test before proceeding...

Once its re-assembled again, ascertain or watch him pressure test the unit. (my F150 is 10 PSI pressure for 10 second's)

[FarOutFlores]

As a general rule, water leaks into the gearbox, rather than oil leaking out! Mind you, anything is possible, is there a chance you didn't refill ot properly when you did the rebuild?

When rebuilt, the oil was filled properly and I personally did the first oil change (noting that the oil was quite pungent and had an extremely dark grey colour). I noted the magnetic screw had a high amount of filings on it from the new wear. I was sure it was filled properly.
The engines are around two years old and have approx. 1600 operating hours.

[FarOutFlores]

When you hear that loud metal to metal banging noise from a LU, it's best to just throw it away IMO.

Do you suggest throwing the entire LU, or just replacing the internal components? If the former, which pieces are worth keeping? Can I put the components in a new lower unit housing?

[bajakeith]

not a lincon log

Unless you have correct tools,shims and know how,,vacuum and pressure tester,, why would anyone mess with one ?? some of stuff posted here is mind blowing..like I've said before,,, " I have a good drill set and a HUGE pair of channel lock's,,need any dental work"

[TownsendsFJR1300]

Do you suggest throwing the entire LU, or just replacing the internal components? If the former, which pieces are worth keeping? Can I put the components in a new lower unit housing?

Even if you have NO idea how the unit works, SHOULD YOU NEED a part down the road, its very possible you may have a good part for the mechanic, sitting in the garage with the old LU.

If the LU housing cracked (corrosion, collision, etc) you just saved $1,000. Bent prop shaft on the new unit, same. You get the idea..


Check e-Bay for LU parts, cases, etc... They ain't cheap.

My neighbor had TWO corrosion cracks on his Suzuki 140 LU (a common issue). A new case is over $1K plus labor. To send out and repair the old one, $800.00. We pulled it apart, sent it out for welding ($75), we did the reassembly, new WP, pressure tested, works great..

Wish we had a spare LU housing...

Before:






AFTER:




Just my 2 cts


.

[bajakeith]

Capt Solo

I will have to agree with you on this issue.. I have been repairing them for 35+ and try my very best to RnR with a new unit (now)..and there are some fine after market with a 3 yr no fault warrenty (not costly) out there..somewhere I have a pic at my old boat yard with 5 on the shelf and one in the clamp's for rebuild..All OMC "stringer" drives (POS).. Do it Once,,Right,, and be done with it,, gear cases take a beating and once beat,, hard to bring back...

[FarOutFlores]

So, I should watch the second rebuild and try to see if the mechanic has the equipment to pressure test the GB. Any other tips before we start?

I'm pretty confident there are no cracks in the LU casing. The mechanic said he thought the oil may have leaked through the upper oil seal (on the drive shaft) as there was damage to the bearing and shim too...

[FarOutFlores]

Unless you have correct tools,shims and know how,,vacuum and pressure tester,, why would anyone mess with one ?? some of stuff posted here is mind blowing..like I've said before,,, " I have a good drill set and a HUGE pair of channel lock's,,need any dental work"

In remote, eastern Indonesia, we have to make do with what we have, both in terms of know-how and tools. I thought a parts forum was a safe place to learn and share ideas..?
I spent $450 on genuine parts first time, then $520 on parts for this second rebuild. I'm ready to try again using the old LU as I am confident it's not damaged (externally). Any useful advice..??

[zenoahphobic]

If one has the right tools, know how and used new parts then it can be assumed it would not leak. Which would make pressure and vacuum testing unnecessary. This procedure is just to be sure for those that have lower level of self confidence.
Do Yamaha actually pressure test their brand new LU , either part of a new engine or as a replacement part?

[rodbolt17]

for the US market, Yamaha does not give any vacuum specs.

reassembling a gearcase isn't hard.
it does REQUIRE an understanding of power transmission via helical cut gears.

checking tooth contact pattern and back lash is easy peasy, if you own a dial indicator and a tube of gear dye.

most techs own neither nor do they understand how to use them.

[zenoahphobic]

for the US market, Yamaha does not give any vacuum specs.

reassembling a gearcase isn't hard.
it does REQUIRE an understanding of power transmission via helical cut gears.

checking tooth contact pattern and back lash is easy peasy, if you own a dial indicator and a tube of gear dye.

most techs own neither nor do they understand how to use them.

Strange the dye pattern technique has been around decades and decades, that many techs don't use it.
I suspect the use of vacuum testing rather than pressure testing, also deludes most, also.

[boscoe99]

There is that nasty word again. Vacuum.

I suspect that they are referring to the pressure outside the gear case being higher than the pressure inside the gear case.

Both propeller seals are positioned so as to be most effective in keeping water out of the gear case. If the seals will hold 10 psi pressure inside the gear case from getting out then maybe the thinking is that they will certainly keep that much pressure outside the gear case from getting in.

[zenoahphobic]

for the US market, Yamaha does not give any vacuum specs.

reassembling a gearcase isn't hard.
it does REQUIRE an understanding of power transmission via helical cut gears.

checking tooth contact pattern and back lash is easy peasy, if you own a dial indicator and a tube of gear dye.

most techs own neither nor do they understand how to use them.

There is that nasty word again. Vacuum.

I suspect that they are referring to the pressure outside the gear case being higher than the pressure inside the gear case.

Both propeller seals are positioned so as to be most effective in keeping water out of the gear case. If the seals will hold 10 psi pressure inside the gear case from getting out then maybe the thinking is that they will certainly keep that much pressure outside the gear case from getting in.

Are you saying pump air into the gearcase to 10 PSI to verify that water can't get INTO the gearcase. Well that's logical!
Why can't they reduce the air pressure inside the gearcase by 10 PSI to see if it leaks inwardly?
Don't techs over there have "vacuum" pumps, like air conditioning trades people have?