Welcome to the site as I see this is your first post. Hopefully the great people here can get you on the right track.
A couple things will help out.
1. What is your OMC model number? It should be one of these:
2. I looked up a couple of these and see that the first three have Prestolite BID distributors in them. Is that correct for your boat?
If yes, review my prior post from (LINK in blue)
1992 5.0L Ford RPM shudder and Trim RPM drop Started by
Offrddrver, July 12th, 2015, 09:21 PM as it may help.
3. Do you have the SELOC OMC Maintenance manual? If so the testing for the Prestolite BID distributor sounds like a good start for you.
4. Once you reach WOT or any cruising speed and you TRIM up or TRIM down, does the motor feel like it is bogging down or high RPM missing? If so, and you have the Prestolite setup, then your issue sounds very much like the one I just resolved. (again, see my post from above)
If you don't have a Prestolite BID distributor, then I will kindly defer to others here at Iboats that have great ideas.
In short, my Prestolite BID distributor shorted Positive to Ground internal to the sensor and that was causing holeshot issues, lightly without pulling, really bad when pulling anyone (even on a tube), was short of power up through the RPMs, and then once it reached WOT it only lost power when I trimmed up or down.
Probably a long shot that it is the same type of issue, but maybe worth a shot to check out.
Best of luck.
Offrddrver
(Prestolite BID picture added and other 1993 distributor added)