i recently purchased two waverunners both are 93 yamaha's one waverunner 3 and one vro pro. when i bought them i replaced motor mounts on both ski's realigned the motors and shafts and made sure they were as close as i could get them to being balanced and inline. also pulled and painted the engines and rplaced exhaust expansion chambers i believe thats what they are called they say yamaha on the top and connect to the exhaust manifold. after all this we put them into the water and they started and ran fine at idle. as soon as we went to get on plane they both would accelerate but not get on a plane almost as if the engine was spinning but the impeller was spinning alot slower. they would rev up and there was alot of vibration but only would do about 5 mph. any input would be helpful. also when i pulled them out of the water they started and reved up and sounded just like they should. thank you again for any input.
