When I removed the cover on the power trim motor a small amount of water had accumulated in the bottom below the armature. It could have been condensation but seemed a little too much water.
Sound like the 'o' ring seal has failed. Should be able to source a replacement even if Mariner don't sell a part. Use a little gear oil or engine oil on the 'o' ring and thread, and tighten down.
Sula
