Leaking Drain Plug
Wow. This goes back 15 years ago but I’m making it my first submission because of all the things I’ve done on this boat, this simple check could save others the most grief.
While motoring along one day, the engine stopped and wouldn’t start or even turn over. Investigation revealed some smoke around the transmission and it was very hot. The engine/transmission seemed to be completely seized up. Time to turn around, set sails and go home. BTW; once in the harbor, a dingy lashed alongside with a two horsepower motor is all it takes to propel a Downeaster 38.
Further investigation revealed that it was the transmission that had seized up due to lock of oil. The engine was ok. Why no oil? It was because of the drain plug sealing ring on the bottom.
The red arrow in the illustration above points to what I’m talking about. The sealing ring (#18) is made of aluminum. It had corroded from salt water (splashed from the prop seal drip) and allowed the oil to leak out. Transmissions like this don’t “use” oil — it only needs oil due to leaks at the seals or elsewhere. This is a big elsewhere that you should know about.
What can you do about this? First beware of any oil leaks under the transmission that might be coming from the drain plug. Seeing or getting access to the underside of the transmission may be very difficult or impossible. If you suspect a leak, I don’t know what to advise other than to check the oil level frequently and keep adding oil. I doubt you will be able to remove the plug and change the seal. I had to overhaul the transmission and I replaced the sealing ring with something other than aluminum. With preparation, you could lift the engine/transmission and change the seal in an afternoon. I had to take it all the way out. It sounds scary but it’s not that bad and a great opportunity to dust under the engine. 🙂
FYI; Here are the particulars of the transmission on my Downeaster 38.
Model HBW 10-2r which is same as newer model HBW 150 now sold by Hurth.
Part number 947.40
Reduction ratio 2.136 (22/47)
Right hand rotation.
Propeller is three bladed 16″ diameter x 13 on 1″ shaft.
Not all boats are the same. See here.
Here is a pdf with scanned pages from the Hurth transmission overhaul manual concerning normal operations. (i.e. how to check oil, capacity, oil type, etc.) .