I posted originally in the Formula section but wanted to open this up to all ideas.
There's a fast trickle in both transom assemblies that looks like it's right near what I think are the exhaust block off plates. I would think with these block-offs that an exhaust bellows wouldn't be necessary but it looks like my outdrives had them at one time but all that's left are the torn remnants still clamped to the transom assembly; nothing on the drives themselves.
I've only had it since Oct and started noticing it more when I started ramp launching with the drives up.
Besides the idea that I'll probably have to remove the motors to get in there, does anybody think reinstalling new exhaust bellows would stop the leak? I think I can do that without much labor right?
BTW, the other bellows, shift & driveshaft, looked OK, but I guess it's possible the shaft bellows could be ripped?

Anything is possible. How old is the boat ? The old style block off plate were thick alum. They corroded after time & new style is a stainless plate.

The exhaust bellow would have nothing to do with a leak wether it's torn or not. The u joint bellow is another story alltogether.

What with lack of easy access to that area with the engines in, plus all the black (darkness induced by paint ) that's going on in that area , it's really hard to make an accurate call.

Don't rule out an aged or failed gasket on the transom plates
I believe that the two lowest bolts on the trans plate are more prone to possibly causing this problem also.
And lastly don't forget the seals/bearings for the steering shaft that passes through the trans plate. Very common.

IF the boat had exhaust bellows at one time, and you said they did. It sounds like both block off plates where installed and probably leak.
I would back the boat into the water at the launch and see if you can see the trickle. Since you say both engines what is the odds a leak from another area (drive bellows as an example) would happen at the same time.
In most cases you would not have to remove the engine all the way from the boat. You should be able to lift it and pull it forward to get at the plate. Not a simple job but not as hard as pulling the engine out of the boat.
Good luck.

1991. What year was the changeover?

I guess I need to look at a transom assembly to see where/how water would drain when it leaks from different places. I could see that the water was leaking from within the assembly, down where the driveshaft and exhaust passages are.
Can the driveshaft bellows be replaced by just pulling the drive? That'd be nice, but I still think it's the block off plates leaking.

BIGJIM, that's exactly what I did last weekend before heading out...backed it in enough to float transom and then hopped in and looked. It sucked to see water coming in from both sides.
Crikey! I won't mess with the block offs until it's time to re-power. I wonder if I can cap the outside of the exhaust passage?

If you remove all traces of the the un-needed exhaust bellows and dry the area well , you could put a seal around the plates from the outside using 5200 . If this IS where the water is leaking in, ya oughta be good to go again !

Madbouyz, help me out here...the pictures aren't great, but ya' think I can get in there and try and seal it up? I'm not seeing how I could do that.

From looking at the second picture you should be able to look and see where the water is coming from. Is it below the drive shaft? Is it at the drive shaft? Is it above the drive shaft?
If the one of the block off plates is corroaded that could fill a boat up with water real fast.

If it is the block off plates, either pull the engines far enough to replace or try sealing them fom outside. The exhaust bellows makes no difference. I would suspect the driveshaft bellows are shot though. With the drives trimmed all the way up, use your hands to feel the valleys on the underside of the bellows. Feel for any holes. If they are more that a few years old they are suspect anyway. From the look of the nuts on the drive, I suspect that they haven't come off in a few years, so pulling them isn't all bad. Another clue to it being the driveshaft bellows is if you are getting a growl out of your gimbal bearings. If the bellows leak, the water will run through the bearing and rust it. You'll hear that when you trim or turn mostly.

Rene