Hi all,
New to the forum and will appreciate any help.
Purchased our Voyager several years ago and have always had issues with it getting up on plane.
Believe the engines are Cruisader 350 XL, 260 hp.
In 2020 blew the Starboard engine, reason was never determined (except it happened right after the carburator and timing was tuned by mechanic).

Decided to rebuild both engines because I didn't want an offset in the throttle. All went reasonably well, got up on plane for the 1st time ever - mechanic put in 750 double pumper Brawlers (vehicle carburetor). The issue became oil pouring out everywhere, rocker arms burning up and found out the wrong size rods had been used with small pieces of washers found under valve covers.

Found a new mechanic and rebuilt for the 2nd time. Engines run great but max RPM is 2900, should 4000 - 4400, as a result can't get up on plane.
Have tested all possible mechanical issues. Have pulled it out and bottom painted, put in rebuilt carburetors (Rochesters). Have spent more money than anyone even imagine.
Really love the boat but need to get to the bottom of the issue.
Props are 18 × 18, have been told by the prop guy to try 14 x 12, again more money spent without knowing if it will work.
Loaded boat weight is 18,000 lbs. Gear ratio is 1:1. WOT is 10 knots at 2900 rpm

Anyone have any other ideas, I'm at my witts end!