And did it leak oil when you were done? It just seems like it would be hard to get the oil pan sealed. Merc 575's, they need some roller cams

it's so easy to pull a motor, why would you try to do that IN the boat and risk any type of failure????

Yes, I've done it. No leaks. Timing cover was a little difficult to get back on because the pan gasket I have is extra thick in the front and needs to squish. I'm used to working on the junk cars and diesel trucks we have today so it really wasn't that difficult of a job for me.

I pulled one tied to the dock at the bar. I trimmed the cover to get it back on. But I agree it's so easy to pull them is much rather do that.

It is actually really comfortable in my Bildge and I like beeing there.

I've done it with the engine in the boat and by having it pulled. Both were single engine boats. I did not remove the oil pan on either one and didn't have any leaks.
The secret is to trim off the corners on the inside lip of the timing cover and loosen the front 4 bolts on the oil pan.
These were both Gen V engines. I don't know if it would work as well on Gen VI's.

Personally, I would just pull the engines and do complete top ends with valve jobs and head gaskets.

back to orig question; do you have enough distance in front of motors for cams to come out?

Buddy did it in his 25' Checkmate on an HP500 Carb punched out to a 509. He pulled the back seat out to do it.

Having done it both ways, It was a hell of a lot easier out of the boat. When I did them in my boat, I pulled the back seat & cut access holes to slide the cams in and out. In addition to pulling the back seat & cutting the accesses, I then also installed access cover plates. all said and done, in hind sight it would have better to pull them and have lots of room to work. I'm 6'3" 250, so room is nice to have. That being said, just bite the bullet and pull 'em. You'll spend about the same amount of time pulling and re-installing as you would trying to fish what ever you drop out of the bilge....

Take the motors out!