lower unit Id 300 hpdi

[formula29]

so I have been chasing a low rpm problem on one of my engines since I bought them used a few months ago, I think I just found the problem, I think I have different lower unit's,, the only numbers I can find are under the zinc, my port one says z9d and the starboard says d7c, do these numbers mean anything to anyone?

[boscoe99]

The casing numbers that I am familiar with can be viewed with the lower unit removed and looking down into a cavity that is aft of the exhaust port. A Z300casing would normally have the letters 6D0. What do you see on your port and starboard motors?

It is not uncommon for gear cases to be swapped around from model type to model type. A number of V6 gear cases are interchangeable with one another.

[formula29]

I found the 250 lower did not have the copper water pipe for preasure relief like the 300 does, you can see the water inlet right through the prop on a 300, what a pain in the ass this was!