Minor tansmission fluid leak

[Paul Cossman]

I have a 1991 Hunter P42 with a Yanmar 4JH2TE (62 HP turbo) that has about 3200 hours on it. I am getting ready to cruise the South Pacific, and am performing routine maintainance on the engine in preparation for that trip (replacing mixing elbow, testing heat exchanger,rebuilding turbocharger, etc.).I have a transmission fluid leak that appears to be coming from the rear transmission seal. It only leaks about 3 or 4 drops per hour, not even enough to cause me to top off the transmission fluid level after the last 100 hours of engine running time. Should I be concerned enough about it to replace that rear seal? Or should I just put up with the minor leak?

 

[Gordon Torresen]

gear box leak

It would be hard for me to say how much of a drip you can tollerate. The leak probably will not get better on its own and could worsen. There are two places that could cause a drip at the rear of the gear box. The seal obviously, but there is an O ring inside the front coupling half where it fits on the output shaft spline. If your leak is coming from between the flanges, the retaining nut could be loosening and allowing oil past the O ring. The tightness of the nut should be checked, for sure, if the leak is between the flange halves.  While you are checking the nut, you might just as well change the seal. Taking the coupling apart and finding a wrench to fit the retaining nut is more than half the job. After the coupling half is removed, the seal can be removed and the new one, and a new O ring, can be installed. One less concern for your cruise, which most of us just dream about.

 

[Paul Cossman]

Thanks, Gordon!

Thanks for the reply.