Gearbox woes; unexplained oil leak

[Nautical]

QUOTE "Now let me bring up a question. Rubber seals and such wear with the passage of use and time. Impellers for instance. Which, of course, are stated to be inspected and replaced on a periodic basis. Not so with the propeller shaft seals. Are the propeller shaft seals less important that the impeller is?"

A good point , but I think there are two different rubbers at play here. One is designed to be more flexible and possibly a softer compound that has to deal with a torturous environment of moving in and out and high speed revolutions and dealing with sand and grit at the same time.The other has a somewhat simpler working environment which is perhaps why the impeller requires more frequent inspections and replacements.

[zenoahphobic]

I also think that seals need to bed in somewhat. They also grind a groove over time but still seal well.
Then when a seal is replaced it won't exactly fit onto the shaft requiring some wearing in. My personal experience often has been that the new seal often does not seal better than the so called old worn out seal. It seems at every seal replacement the shaft also needs some attention, if not replacement. Those that have worked on motorcycle waterpump probably have experienced this.
In regard to brake calliper seals, as pads wear the seal travels into areas where minute or even great corrosion has occurred from water absorption in the fluid. So the thinking would that they have a hard life!

Back to lower units the worry about pressure differentials could easily be resolved by a venting tube; so why don't manufactures provide this?

[boscoe99]

I also think that seals need to bed in somewhat. They also grind a groove over time but still seal well.
Then when a seal is replaced it won't exactly fit onto the shaft requiring some wearing in. My personal experience often has been that the new seal often does not seal better than the so called old worn out seal. It seems at every seal replacement the shaft also needs some attention, if not replacement. Those that have worked on motorcycle waterpump probably have experienced this.
In regard to brake calliper seals, as pads wear the seal travels into areas where minute or even great corrosion has occurred from water absorption in the fluid. So the thinking would that they have a hard life!

Back to lower units the worry about pressure differentials could easily be resolved by a venting tube; so why don't manufactures provide this?

BRP with the Evinrude G2 does. Sort of. In a fashion. There is a gear oil reservoir on the motor that holds gear case oil. If and as needed gear oil can flow down to the lower unit. As the pressure in the gear case rises and falls operationally the oil level in the reservoir will rise and fall. There may even be a sensor switch in the reservoir that alerts the operator when the reservoir gets low on oil.

Now having said this, there is some benefit to have a bit of positive pressure within the gear case. The benefit being that the oil pressure will help in keeping water from getting in. The weight of the gear oil from the reservoir in the BRP G2 causes the 2 gear case to always have a bit of static pressure.

Another question is why are outboard motor manufacturers so slow to adapt to newer and better technology such as the gear oil reservoir? Yamaha particularly seems to lag behind the others. Woodruff keys driving water pump impellers? How archaic.

[zenoahphobic]

BRP with the Evinrude G2 does. Sort of. In a fashion. There is a gear oil reservoir on the motor that holds gear case oil. If and as needed gear oil can flow down to the lower unit. As the pressure in the gear case rises and falls operationally the oil level in the reservoir will rise and fall. There may even be a sensor switch in the reservoir that alerts the operator when the reservoir gets low on oil.

Now having said this, there is some benefit to have a bit of positive pressure within the gear case. The benefit being that the oil pressure will help in keeping water from getting in. The weight of the gear oil from the reservoir in the BRP G2 causes the 2 gear case to always have a bit of static pressure.

Another question is why are outboard motor manufacturers so slow to adapt to newer and better technology such as the gear oil reservoir? Yamaha particularly seems to lag behind the others. Woodruff keys driving water pump impellers? How archaic.

Yes, the principal of oil reservoirs feeding wheel bearings is well established in the trucking industry as well kits available for humble domestic trailers including boat trailers.

[DennisG01]

Mercruiser has been using a remote-located gear oil reservoir for a couple decades. It's a lot like what you're describing. A plastic bottle, filled with gear oil, mounted on a bracket at the engine. From there, a tube connects it to the lower unit. For the same reasons you mentioned above, in regards to pressure being better, the bottle has a one way valve that allows air to enter, but not escape -- with the idea being to eliminate vacuum and allow positive (or at least zero) pressure inside the gearcase.