Twin Mercruiser 5.7L Engine Performance Issue - Troubleshooting

Question
I HAVE TWIN 5.7 MERCRUISERS - THEY RUN GREAT EXCEPT FOR AT TOP END. THE PORT ENGINE WILL RUN UP TO 4800-5000 RPM AND SOUNDS GOOD WHILE THE STARBOARD ENGINE DOESN'T WANT TO GO OVER 3800-4000 RPM AND MY SYNC GAUGE REFLECTS THAT. IT SEEMS TO BE RUNNING OK JUST DOESN'T WIND OUT LIKE THE PORT ENGINE. IT IS DEFINITLY LACKING SPEED AT TOP END ALSO. 31' LARSON W/TWIN 5.7 BRAVO 3'S.COULD THIS JUST BE A CABLE ADJUSTMENT?  

Answer
check your timing. check cables going to carb to see if you are going wide open throttle.check props to see if maybe they are out of shape or a spun hub. usually one engine will lag behind the other by 200 or 300 rpm. what has changed since you have owned the boat? weight , trim tabs, etc? do a compression check. hope this helps.

               bruce