Boat sat for a few years. I replaced both long blocks 350 Mag Mpi suck out almost all the old gas. Been using boat for about 20-30 hours maybe ran through 300 gallons but motors don’t feel the same under throttle I bought new props same that were on there I think 3 blade 23p but boat won’t go past 4200 rpms on both motors if I trim high enough I can get to about 4500 but boat will pull super hard to left with little input.
I’m running about 61 where I was around 70 before replacing motors

1. Scan engines and check ignition timing.
2. Check fuel pressure
3. What kind of steering??

No codes cleaned injectors changed filters. One motor has a kink in return line but I have a new hose to put it. I forget the name of the steering but replaced all hoses that goto the rams that connect the 2 motors

If I have same rpms but one motor putting out less power will it cause it to steer crazy at around 50 mph turning right it fine left wants to go super shape
also I gave the pcm555

If one engine was down on power, it would have less rpms. Verify timing is set correctly and advancing correctly.

I'll assume you have either full hyd or add on hyd steering since you said it has hoses. Does it have a cable from the helm or hyd hoses. I'm guessing you have add on hyd steering with a cable from the helm. My friend has a 28zx with add on as well. Have you checked your transom assemblies to make sure they are tight?? Do the drives have a tie bar?? Did you set the toe on the drives??

Was the hull fully supported on a correct trailer when it was stored for several years??

I didn’t adjust tie bar cause I pulled it off the way it was when I pulled drives. One motor runs the power steering to the rams on the back of the boat and then other motor has a loop Around for power steering. I’ll check timing. One motor has more power on take off and the other has more power top end she runs good around 4K but that’s like 56 mph

I have the service manual and then mer computer but my distributor doesn’t have the plugs on them from what most do should I still set motor to service doing timing

X 2 starting with basics
1) timing
2) fuel psi at idle and with under load
3) you got identical motors with what you replaced

Yes both were from mercruiser new not reman it’s hard to check fuel pressure running cause the hatch is open