Bought the boat new last year and had motor problems. The dealer had to rebuild the motor. Yamaha technicians came out and ran it this year and put a different prop on and checked everything. With clean toons Was getting 38 wot with 5 adults. Boat sat in the water for about a month and toons got dirty speed dropped to 20 mph with 3 adults. So we scrubbed them in the water and was and was able to get back up to 34 mph wot. Toons are fairly clean now just seems like the motor is struggling!You should be faster than that with that boat at WOT - even loaded down like that.
On our 24’ SSBXP SPS 200 Mercury Verado Pro a week ago we had a full cottage of family out boating and tubing. With Sea Legs, 10 people on board and a Super Mable with another 3 people on it and I still got to 29-30 mph (I only took it up to that speed briefly with teens, otherwise a bit fast for us tubing). Without the tubing and at 13 we were mid-30’s, and again I have the extra weight of the Sea Legs.
Has it always been this way or is it a new development? If always that way, I’d think prop and motor mount issues. If it’s a new problem, are your toons dirty?