I had to replace the starboard motor and I’m trying to work out some kinks... First two things I need to address are

I can’t get the new motor to spin more than 3,400 RPM- It’s a 5.7/ 350 Vortech motor. I purchased this new from Michigan Motorz and its hooked up to my Alpha 1 drive.
The motor idles smoothly at 600-700 RPM. So dose that rule out a timeing issue?
[url]http://www.michiganmotorz.com/vortec-marine-engine-bronze-package-1967current-replacement-p-59.html[/url

Not necessarily. What is your timing set at?

The marina who put the motor in the boat set the timeing and I didn't see where they set it. I'll see if I can barrow a timing light and check it.

Few things will limit RPM, Fuel flow, exhaust restriction, and poor timing. If timing checks out do a fuel filter change. Is this an EFI motor? Take a look at throttle rigging. You may be pushing the throttle but the carb or AFM may not be corresponding with input.

It was the timing. I'm at 32 advance and now able to spin the motor at 4,500 rpm.