Is there any way to easily check the lift of a cam while the motors are in the boat? My starboard motor pulls very hard, much harder than the port side. I know for sure the starboard has a newer cam and lifter set (long story but this was done three years ago). The port motor is a bit of a mystery to me though. When warming up the motors one at a time at the ramp I can tell a noticable difference in sound. Was thinking maybe there might be an issue with the cam in the port side motor???? The motors are merc 420hp's and run great otherwise. When running my 23 pitch props the starboard motor wants to spin past 5300 and the port signs off around 5100.......Any thoughts/Advice would be greatly appreciated. I believe the 420's had the 731 crane cam installed from the factory. If I were to swap both out what would be a good cam to upgrade to? I really love the sound of the starboard motor, I just want them to run, sound, perform the same.

Th first thing would be a leakdown test/ compression test. as far as checking the cam, if you have a dial indicater with a magnetic base you can check the lift at the valve on each cylinder. a flat lobe will be pretty aparent

the 420 came with flat tappet cam,crane 730 ,i beleive is a hyd roller cam.

I think there is a dial guage you can use to measure the lift by placing it on the pushrod or rocker.

The stock Merc 420 cam is a Crane #132561.
Flat Tappet hydraulic 228/236, .530/.551, 114 lobe sep

Thank you for the input guys. I went ahead and told the engine builder to locate a cam and lifter set. I believe I will run it like it is for this summer and pull it out in the fall. He is going to make me a hell of a deal on a full rebuild at that point.

Cut your oil filter and look for silver cam flakes. If your losing a lobe it will be in there.