Adding a 300 I paid 8k for to get me 900 ponies is a heck of a lot less coin them Merc wants for the 450s and then I have a huge 60% tax when they come into Colombia.

keep in mind that third lower unit is gonna add drag too, so your gains will be affected by that.

exactly. adding a 3rd engine is a huge diminishing return. On the triple outboard cats we used to rig, they would out-accelerate the same hull with twins but weren't as fast you may think. And that's on a cat where the 3rd engine is seriously surfaced. Only worse on a V.

If you’re blowing LUs already it might get more reliable due to less load

If you were starting scratch I’d want 2x merc v10 400s or Yamaha 450s. They’re designed to push heavy boats as they have big beefy LUs.

we have two 42 passenger boats with 18 degree hulls for moving people 1;45 trip to and from my island hotel daily. We bought two pairs of 300s from the narcos. They only use a pair of engines for 1 run apprx 220 hours. We get the engines for about half of what a new set sells for. We just got a sweet deal on five 300 engines minus lower units for 8k a piece. We run Yamaha 300s we run at 4400rpm which nets us 29-30mph. They have 2k hours on the oldest boat. A buddy running the same set up has almost 4K hours on his Yamaha 300s. My personal boat is a manta 32cc with an Armstrong bracket. Importing boats to Colombia is almost impossible to get them legal. We are friends with a captain in the navy here that is getting my manta done after sitting 7 years. So bringing down another boat won’t happen as I don’t want to pay new boat money. I do have a rude 4L 300 v8 2t engine I might buy a new 21ft boat for and have my mid cut down to a 16” mid. Will have an investment house for sale in about two months when I sell that will look at what’s out there for new 21ft ers

32 Manta isnt the lightest boat out there. I don't think you are going to get 70 even with triple 300 yamahas. Dont get me wrong. Wonderfull engines but not exactly performance focused. Take it from someone that took off 3 300xs to go to two 350sci's.