Leaky Lower Unit

[timberxx]

I changed my lower unit fluid for the first time on my F200 about 3 months ago. I have done this service on my old T40 several times.

Since then I have taken out my boat twice.

I noticed yesterday, that I was leaking lower unit lube. I changed both gaskets once the oil was changed. It seems like the oil is coming from the top drain plug.

Opinions? Should I be worried?

Thanks in Advance.

 

[seasick]

Yes.
If the oil is really leaking out of the top plug, water could be seeping in. You need to redo the gasket, it may be damaged. The screw may be cross threaded ( I hope not). The screw may be loose or finally, some crud got under the gasket and is preventing a good seal.
It needs to be looked at.

 

[timberxx]

I replaced the screw gaskets, I really hope I just didn't tighten the bolt hard enough. I did damage I would be pretty pissed at myself.


Thanks for he quick reply.

 

[HMBJack]

I had the same problem. Changed my lower unit oil and it came out milky. I checked with my Yamaha Service guy and he told me Yamaha changed their supplier of gaskets in the last year or so. The gaskets from this new supplier are very, very, hard. So hard that the gasket does not crush and seal when torqued down. As a result, the lower unit screws loosen up due to the vibration.
Until there is a TSB, best bet is to snug those screws up every 20 or 30 hours. This issue of leaky lower units is happening more and more and the only reason my Yamaha guy can think of is the hard gaskets.

 

[HMBJack]

Reference Pacific Marine Repair in Oxnard, California on the above opinion (Tech's name is Alan).

 

[timberxx]

Thanks for the info HMB.

Next time I'm at the boat, I'll change the fluid, and tighten the bolts.

 

[seasick]

Yes, the screws have to be really tight. The secret to doing that without damaging the head is to use a pretty big screwdriver with a thick tip that is a good fit for the slot. You can also put some oil on both sides of the gasket before installing. That helps the screw turn easier against the washer and LU screw seat. Did I mention TIGHT! I will often use a wrench on the screwdriver shaft to make the last 1/8 turn.

I have seen these things loosen up and work themselves out.

 

[lgusto]

Working on something this important, and this expensive, seems to beg for a torque wrench set to proper specs. Anybody have experience with this approach? What would Yamaha's engineers suggest?

 

[seasick]

I pretty much torque everything on my motor EXCEPT the LU oil screws. Why? I don't have a flat blade screw adapter that fits my wrench. In addition, it is tougher to use a wrench on those flat slot screws without the bit skewing out. A long big screwdriver works best in my opinion.

Overtons used to see Yami LU screws with allen screw heads . The non magnetic upper is still available but the one with the magnetic tip (lower) is not and I can't find it anywhere. If anyone knows of a source of the allen head mag screws, chime in. They are so much easier to use