F250 lower unit oil

[DennisG01]

The Merc Hi-Perf (synthetic) stuff is a greenish-blue, as compared to the "normal" looking oil (dino) color of the regular stuff. There's no way you'd confuse the two - by the sounds of it, you definitely don't have the Hi-Perf stuff in there.

The Merc Hi-Perf stuff is indeed a synthetic, but it is GL4 rated, not GL5 like some synthetics (this is what Rodbolt was warning about).

[boscoe99]

It is not a synthetic versus non-synthetic issue.

It is a GL-4 versus GL-5 issue.

[pstephens46]

I am not convinced your seals are leaking yet. One step at a time. Soap or tank, whichever you decide.

[scofflaw]

How bout some scientific explanation how oil can eat bushings. Not buying it myself

[fairdeal]

How bout some scientific explanation how oil can eat bushings. Not buying it myself

I'm generally a sceptic (skeptic?) but I "buy" it

Here's some excellent reading:

http://www.widman.biz/uploads/Transaxle_oil.pdf

[rodbolt17]

because I destroyed a friends lower by using the Volvo GL-5 synthetic.
peeled the busing out of the fwd gear.
when I asked at the Yamaha drive train school a few years back the instructor called engieneering and that is what he was told.
the molecular structure wont properly lube bronze and some additive packages actually react with bronze and eat it.

while I am a lowly master tech I did see first hand what it does.

[JackintheBoat]

The reply on here making sure my pressure tester itself was not leaking was spot on. I tried it again last night and the hoses were not tight and the fitting would not screw tight to the top vent hole b/c of the cavitation plate. I simply put my finger on the Mity pump without the hose and it held pressure. So I made sure the hoses were tight and attached it to the drain plug at the bottom, and it held pressure barely even falling much (or very slowly) so I am pretty confident the seals are fine.

As far as the gear lube, yes its a greenish blue and is the quicksilver hi perf, my local yamaha shop sells the same stuff in bulk so I know I am using the right stuff.

As far as this last lower change with the oil being brown, I will say the boat has been run hard the last 5 months (hi-speed *****ing for wahoo) and we have long runs to the fishing grounds. And I have read the LH counter unit works harder with less oil capacity than the standard unit, thus the oil becoming "used" in color much like engine oil. No doubt I will inspecting the oil every other trip and changing it out at the 50 hour intervals.

So at this point with no signs of water instrusion and seals that seem to be ok, just gonna fill it back up and go.

thanks for all the input!

[pstephens46]

Change it more often. Oil is cheap....

[DennisG01]

What are the specs for your engine in regards to VACUUM testing the lower unit. Pressure testing is one thing, vacuum is another.

I've changed a lot oil from gearcases that use the Merc Hi-Perf stuff. Now, I'm not saying that I've seen everything, but I have yet to see it turn brown. Black, yes, but not brown. Water intrusion will cause it to turn light green in color. Who knows... maybe black + water = brown in this case?

I'm at a loss on the lesser capacity. I googled and found a chart that shows the difference and there is a 5oz difference. I don't know why it is, but it seems you are indeed correct on that. Last page: http://www.yamaha-motor.com/outboard...ce_matters.pdf

[boscoe99]

What are the specs for your engine in regards to VACUUM testing the lower unit. Pressure testing is one thing, vacuum is another.

Yamaha does not provide any specifications for a negative pressure test.

Both propeller shaft seals are oriented so as to do a better job of keeping water out than keeping oil in. If the seals can hold an internal pressure of 10 psi, then the inference is that they will do an even better job of keeping water out.

Some engine makers orient one of the two seals outward and one of the two seals inward. In that case I suspect both a positive and a negative pressure check would be warranted.

[boscoe99]

As far as this last lower change with the oil being brown, I will say the boat has been run hard the last 5 months (hi-speed *****ing for wahoo) and we have long runs to the fishing grounds. And I have read the LH counter unit works harder with less oil capacity than the standard unit, thus the oil becoming "used" in color much like engine oil. No doubt I will inspecting the oil every other trip and changing it out at the 50 hour intervals.

The counter rotating gear case is not working harder but it does have more parts inside, thus it can hold less gear oil. The extra parts, coupled with less oil, for some strange reason seems to have an affect on the oil changing color sooner than it otherwise would.

[pstephens46]

The counter rotating gear case is not working harder but it does have more parts inside, thus it can hold less gear oil. The extra parts, coupled with less oil, for some strange reason seems to have an affect on the oil changing color sooner than it otherwise would.

More bronze parts in the counter rotator?

[DennisG01]

Yamaha does not provide any specifications for a negative pressure test.

Both propeller shaft seals are oriented so as to do a better job of keeping water out than keeping oil in. If the seals can hold an internal pressure of 10 psi, then the inference is that they will do an even better job of keeping water out.

Some engine makers orient one of the two seals outward and one of the two seals inward. In that case I suspect both a positive and a negative pressure check would be warranted.

Now that you mention that, I think have heard that before... probably on this forum!

[99yam40]

More bronze parts in the counter rotator?

I do not know, but it is good to check what your lower has in it and look at the recommendations from Yamaha before putting different lube into it