I have a 16ft tri hull with a merc 65 on the back. It's a 1975 650. I cleaned the carbs, rebuilt the fuel pump, replaced the plugs, checked to see if they would jump a 7/16" gap, cleaned the cap, replaced all the fuel lines, took the cap off the tank to make sure it's vented, the compression is 150 on all cylinders, and did a link and sync. There is a 14deg prop on it. My problem is that it will only get on plane when we have two people or less in the boat. Shouldn't this motor be able to push this boat better? I went through everything and it's not made a difference. Also I adjusted the throttle to make sure they're opening all the way. The timing is 23deg at full throttle. Please help!!!