Yep, I have killed two motors in two years due to thrust bearing issues. The first was due to the thrust bearing in the pump itself going bad due to the grease monkey not doing his job. The second, I think, following a pump rebuild, was due to soft stringers and resultant flexy motor mounts letting the motor move back under acceleration, at least, and maybe also while turning, putting forward load on the thrust bearing of the engine. And there 'ya go, another one bites the dust. Thrust bearing debris kills cam lobe, and there's 1/16'' end play on the crank. Structural work on the boat underway. To maybe answer the question of how you can check thrust bearing condition, open handhole cover, insert hand, grab shaft and try to move the shaft front and back. All males should have a good grip on this technique. All gals should too. Any end play would not be good. in the pump, that is.