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bobk
Senior Member Posts: 1,172
Join Date: Aug 2005

Allison M15 won't go forward - 11-09-2010, 11:45 AM
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Hi Guys, we are about 80 miles from home after almost 1000 miles, fueled in Canaveral and lost the foward gear on the starboard engine when we undocked. Reverse works fine and the gear oil pressure is normal. The shifter seems to be moving the shift lever properly and the shaft is also rotating as it is shifted. Oil level is proper. The prop seems to be turning slowly when the engine is revved up in foward. Any thoughts? Mechanic recommendations in the area if this is serious?

Bob Kassal
Chateau de Mer
1981 48MY
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HERE IS AN UPDATE: Figured I'd start again since the other post morphed into single screw handling.

The on scene Cummins mech (Dennis) tried raising oil pressure as it was a little low. The pressure drops down when engaged, and doesn't rise significantly when left in gear.

He also cleaned the screen, but found just a few bits of debris. No blockage. The prop turns normally in reverse, but much slower in forward. The oil is clear and has no odor.

When cold the next day the forward gear engaged normally, but once again was kaput when it warmed up. The DD mech (Ken) noted the oil was frothy with air, and eventually suspected the oil pump might be at fault. It has been pulled and is being checked at a repair facitity. I believe they consulted with Allison before doing this. They are checking out the simple things before tearing into the transmission.

Bob Kassal
Back in Port St. Lucie with the boat in Canaveral