I think you need to get it out of the water and push pull side to side and up and down on the drives, there should be no movement

Just thinking out loud here. When cone clutches fail, it causes a delay in shifting into forward or reverse. I have never seen one slip while under way. I would rule that out.
I don't believe the drives would be raising while under power. The force of forward thrust would push the drives down, not raise them. It this was happening, you would be able to see it on your drive indicators.
I don't think the engine couplers are stripped. When they fail, they fail. No movement at all.
I believe that you have some serious prop cavitation going on either from the drives not going down all of the way, some improperly installed drive showers or something of this nature. Another possibility would be the bottom of the hull is in worse condition than you think it is. Very dirty, algae or barnacles growing on it or something along those lines.
I am surprised that it has 3 blade props on it. What are others running on this hull?
Boat could be waterlogged and so heavy that it just can't go.

Did I read correctly that you had a Formula 311 on plane, with one engine? A 330 at that?

lol yes but to clarify, I had the second engine running as a booster. Just didn’t want to take it over 2k rpms because of an exhaust leak.


NOW, on to what I’ve discovered today. I had the boat hauled out to see if the drives were slipping in any way. They are not.

But I have found the source of the problem: the barnacle company that’s been diving every month has been scamming me.
Take a look:



https://cimg8.ibsrv.net/gimg/www.off...1b9720ca4.jpeg


So the drives are all right with no play. I spent a few hours pressure washing the barnacles off the hull and I’ve got a buddy who’s going to do the bottom in an ablative paint in the next week or so while she’s out of the water. Hoping that solves all the issues.

Omg

Whoa!!

Is there anyway to keep her out of the water when not being used?

Couple of observations, those props are not your friend. Get some Bravo props or Mirage 3 blades. Check the operation of the tabs and indicators. Painting the bottom will scrub 3 or 4 mph from you but at least you shouldn’t have this mess again for a while. Remember that frequent use of the boat is your friend and leaving it sit in the water has its disadvantages.

Bud - keeping that in the water is going to create the worst boating experience you could ever ask for. Before long you are going to be longing for the days when getting on plane was a concern. If you have to keep an I/O boat in salt water you need to sell it and get a boat that’s appropriate for your circumstances.

so, for my own instruction, having this bottom like that could be enough to stop a boat from planning? even though there is 640 hp pushing it ?

Is there a marina close by with in/out service? Wouldn't have to paint the bottom.