So as title describes I've been through the ringer restoring a 1999 260 da. Bought it from a friend for cheap with a blown up carb 7.4 in it that blew up on him after only a couple trips after he repowered his blown 5.7. How can a person blow so many motors. He blew up the original motor with only around 375-400 hours then blew up the repowered big block with only handful of hours and then in a twist of irony after I finally got the 7.4l "performance tuned" motor that I bought advertised as used with low hours I let him take it out figuring if anyone knew how to run the boat it would be him and after a few hours it blew up on him on the way home. Low compression on 3 cylinders. 2 on starboard side one on port. Completely blew out a spark plug like ive never seen before. I'm way too deep into this boat already. Hindsight being what it is, I would have bought a new crate motor from the get go. Had a shady mechanic install this and they lied about tuning it and giving it good work through. New mechanic has been great and we sorted out multiple issues including rusty carb and fuel pump (motor must have had water in fuel at some point), leaking sea water pump, bad thunderbolt ignition module, bad cap and rotor and lastly, an apparent case of bravoitis. I'm now into this boat for 31k which includes full cosmetic refit so now crate motor is out of the question. Anyone got tips for rebuilding this 7.4? Apparently "performance tuned" means it's got peanut port heads on oval intake. People poopoo peanut ports but apparently they make great torque and this application was created with cruisers in mind. Most likely has cast internals but rebuilding I can change all that so what is best way for me to get some more power out of this? I know it's a big heavy cruiser but not gonna lie, was disappointed with it topping out at 35mph at 4250rpm which was right on the 42-4600 rpm spec with the 24 pitch bravo 3 props. We did have 4 guys on board during the sea trial but still if that's top end is my realistic cruise only gonna be 25mph? That sucks for a guy coming from center consoles. Anyone rebuilt one of these? Supposedly even with cast internals the motor should be good to go north of 400hp. It's guys going crazy trying to get 5-600 hp with blowers that need the forged stuff. Open to all ideas. Quote to rebuild is appx $3000 without builder seeing it yet. Mechanic should have it out tomorrow and rebuilder is in the same industrial park. Reputable rebuilder here in Tampa though i do need to make sure he is aware of marine specific needs like not going too crazy with cam and making water reversion possible. Anyone ever see a spark plug blow out like this? No water in the oil which is good but what would cause this? Friend said they cruising along heading back to ramp when it started making a sound of air like a steam engine which must have been the plug blowing out of the cylinder and piston pushing air. He immediately shut it down and then it wouldnt restart.