‘92 SN PCM 40a Transmission Leak?

Hi all, first time posting and glad to be here. Bought a ‘92 SNCB two weeks ago (my first boat) with 440 engine hours on the 5.0 351w. Finally got it out to the lake this past week and discovered a transmission leak—here’s what I know:

- It did not leak when I test drove it before buying, but we drove it 10hrs on the trailer before putting it in the water again. Otherwise not sure what could have caused the leak.
- PCM 1:1.23 40a Transmission (says 40 on the plate but I think the a is just rubbed off? I cannot find any evidence they ever put the 40i in SNs).
- Looks like it is dripping down the bellhousing from the front of the transmission (aka front seal leak). We are far from home so have been checking/adding dex/merc ATF as necessary and drill-pumping out the extra from the bilge into a bucket to keep it running smooth and not pollute.
- I haven’t been able to do the cardboard test to identify exactly whether it is front or rear since it’s been in the lake, but have seen dripping from the bellhousing and nothing from the back when engine is running in neutral.
- I know I’ll need to take out the transmission to change the front seal, which I feel somewhat confident in doing thanks to Kevin’s blog post from a few years ago and Vince from SKIDIM’s video on youtube.

What I don’t know/what I could use help with:
1. I think I need a front seal but SKIDIM/Nautique Parts are less clear on the exact front seal I need vs. the rear seal (which is very clearly marked). My “Parts” section of the 92 manual is just about the trailer and doesn’t have any inventory list.
2. Should I also replace the rear seal while it’s out? I know that generally it’s not worth it to replace things that aren’t necessarily broken since these are relatively reliable boats, but would prefer not to take the transmission out more than once and the boat is 32 years old.
3. I know from reading Kevin (KRoundy)‘s blog post from back in 2016 that what appeared like a front seal leak was not from the front seal but from a gasket misalignment—how do I go about figuring out where the leak actually comes from?
4. Where should I hook up a hose to run the engine out of water on the trailer? I know where the impeller housing is but don’t know if that’s considered the RWP and whether to hook the hose up to the bottom of that housing.

Appreciate any help you all can give. I’m good at internet sleuthing but this is my first boat and I don’t have any experience with working on engines or boats (but I do want to learn). TIA for any responses.

Here's a link to a YouTube video on rebuilding a 40I transmission. 

FFImarine wrote: All PCM 40 series transmissions take the same oil pump seal. Give me a call tomorrow and I can either sell you a seal or show you which one it’s is on SKIDIM website 330-273-8291

I’ll give you a call tomorrow—will come from (801) number.

Did you check your damper plate?  The reason I ask--early 90's I was grinding pumps on my velvet drive and there was no internet to ask....that bad damper was the root cause of many dollars in repairs.