Shift shaft seal leaking?

[Bryanmc57]

2006 200hp optimax 1B378098

Replaced my impeller and associated parts the other day. When I dropped the lower I noticed a light covering of fine sand (Colorado River, lots of fine sand in the water) stuck to the outside of the wp housing and shift shaft cover. It was stuck on by what felt like gear oil. There was also about a 1" band of it stuck about 1/2 way up the driveshaft. When I changed the LU oil, there was a small indication of moisture (small white stripe in the drain pan, but no actual water was observed when the drain plug was removed. There was no evidence of oil inside the impeller housing so I'm "assuming" that it's not from the driveshaft seal and since it's not high on the driveshaft so I'm again "assuming" that it's not the lower crankshaft seal. I'm thinking it must be the shift shaft seal.

Does this diagnosis sound reasonable? I know the best way would be to drop the lower and pressure / vacuum test it but I don't currently have access to the necessary equipment.

On a side note (I've always wondered) the impeller has a horizontal seam through it about 1/4 way from one side. Does it matter whether the bigger side is up or down when installed?

[Savage]

Pressure testing is the only way to determine a leak.

[Bryanmc57]

Pressure testing is the only way to determine a leak.

While I agree completely with this statement, how many ways are there for gear oil to get on to the outside (not inside) of the water pump housing and the outside of the shift shaft housing?

[Savage]

1. Overfilling
2. Worn shaft
3. Cracked housing
4. Defective Seal

[Bryanmc57]

All good points. Pretty sure it's not from overfilling but the other three are contenders. Nearest mercury dealer is a couple hours away, maybe if I get lucky someone here locally can test it. There aren't any boat dealers here at all.

[OldTimer57]

not to mention bad seal on either drive shaft below water pump or the shift shaft seal. And it could be DFI oil from above as well, which will feel pretty similar when mixed up with sand.

Always best to apply correct diagnostic procedure before fixing something that can have multiple causes, particularly when some of the causes are cheap repairs and others are not.

[Gamblinman]

All good points. Pretty sure it's not from overfilling but the other three are contenders. Nearest mercury dealer is a couple hours away, maybe if I get lucky someone here locally can test it. There aren't any boat dealers here at all.

You would be surprised how many get overfilled. Why I always recommend taking it out and getting the LU oil warm, put it back on the trailer, and crack the vent screw and let any pressure and excess oil run out, after changing LU fluid.

[Bryanmc57]

You would be surprised how many get overfilled. Why I always recommend taking it out and getting the LU oil warm, put it back on the trailer, and crack the vent screw and let any pressure and excess oil run out, after changing LU fluid.

Interesting but the manual doesn't call for that. Last time I filled it before this last service was in Mineola, TX. Here in AZ, the temp during the daytime makes the lower unit too hot to touch (boat is currently stored outside with the cover on it until my shop is finished). Wonder if it's an expansion issue.

[Savage]

It is an Expansion issue. If you fill it properly there is room for expansion.

[Bryanmc57]

Have I been doing it wrong all these years? I fill it from the bottom until it starts to run out the vent hole. Then I put the plug in the vent hole and remove the filler and put the plug in the fill hole. I thought it was only the torquemasters that you were supposed to let an ounce or so drain out before you put the fill plug in. I've been doing the lower unit oil on this motor for 13 years this July and never had an expansion issue. Could it be this blazing Arizona heat causing my problem?

[Savage]

Yes. I would check level in the heat of the day.

[Bryanmc57]

Yes. I would check level in the heat of the day.

OK, so heat of the day crack the vent screw and see if oil flows out?

[Savage]

OK, so heat of the day crack the vent screw and see if oil flows out?

Yes.

[Bryanmc57]

Of course we're getting an unusual cold front here for the next few days. Not forecast to get past the mid 80's for almost a week. As soon as it gets up in the upper 90s again I'll give it a shot. Going forward, do you recommend draining 1-2 ounces after a normal lube change (as I mentioned earlier, I had heard that about the TM lowers, but never the verado style)?

[Savage]

Missed that you had a Verado…...Don't drain out any additional fluid.

[Bryanmc57]

Missed that you had a Verado…...Don't drain out any additional fluid.

OK, got it. I'm pretty sure it's the verado style lower. 2006 200 hp optimax not a pro xs motor, not a fat shaft. PN 859399T13 I believe.

[Bryanmc57]

Followup... The temp finally went up again some, 96 in the shade and the motor is in the sun. Leveled the motor with a level on the cavitation plate and cracked the vent screw. Heard a distinct sound of pressure being released and probably 1/2 to 1 ounce of gear oil ran out. I'll drop the lower and change the gear oil in a week or so to see if the problem has resolved...

[OldTimer57]

Main thing is "cavitation plate level (same as propshaft level)." Then leave vent out until nothing dribbles out of the hole. If the L/U is not level, all bets are off and you run the risk of over-filling which can cause you to push seals out as fluid expands. Slightly underfilled is not such a big risk. But to baby bear it and get it just right, make everything level, fore/aft and left/right.