Can't find oil leak

[DickB]

My 4 year old SEI drive started using oil a few weeks ago, to the point where the reservoir would empty within 15-20 minutes of use. I replaced the shift shaft seal which was showing bubbles on a leak pressure test and also the o ring at the oil passage. I did not see any more leaks on pressure test. Back in the water it was still losing oil. No oil visible anywhere.

I threw in the towel and took the boat to the local shop. They replaced the seal under the water pump that was crooked and thought they had it, but no. The also replaced the prop shaft seal. They say pressure test is fine. Also pressure tested the reservoir to drive. They ran the boat at fast idle and no leaks, but under power it is still leaking.

The shop manager suggests swapping with another lower to isolate the problem to upper or lower. The manager thinks maybe something is cracked and opening up under pressure. I probably owe $300 to the shop at this point. The drive is together on the boat. I asked them to discontinue work. I have the original lower and could perform the swap. A gear in the original upper threw a tooth and there was casing damage with metal particles - a concern is that the lower may have gotten contaminated with metal particles.

Looking for suggestions on how to proceed to try to find and solve this problem. What do you think about the lower swap?

[admin]

The lower swap is a good idea, just flush it out with a little lube before installing it. One thought would be the shift shaft bushing may be leaking when you shift. When pressure testing you should always twist, pull and push on everything to see if you can find a weak seal.

Tech Support

[DickB]

I did exactly that last week. Flushed the original lower with oil and installed it. Pressure tested it first and it was rock solid. Ran a good hour at speed with no drop in reservoir level.

I can't say how the shop pressure tested. Although I got back on the water and in that sense solved my problem, the SEI lower is not fixed. It is still puzzling to me that they say they checked every seal, pressure tested and passed, but the drive still loses oil at speed. And a lot of oil - the reservoir gets drained after 20-30 minutes of running.