Need info, engine running 4200 at WOT

[txtaz]

Hey everyone,
Just getting the boat into shape and had it out today for the first time at WOT. It only did 62 MPH at 4200 RPM WOT. I know the optimum range is 5000 - 5200 RPM. I had the boat up to 65 before it went to the shop and still had throttle left. I'm a litttle confused.
For a little background:
I cleaned the cap and rotor, replaced the water pump. I'm getting a new cap, rotor and thermostat just to be safe.
Indications:
Motor runs cool ( 130 ) gets to 150 after a hard run and then cools down to 130 again. Thermostat???
The motor hasn't been run hard before because of the build up on the cap and the plugs. Bad spark.
Can the ECM limit the RPM's if it thinks the engine is cold?
It's a 350 MAG MPI Bravo 1 with a 23" Mirage Plus.
Thanks for the help.
Wes

[RedDog]

Your obviously telling us speedo speeds vs GPS speeds so its hard to figure what if anything is wrong. At 4200 RPM you are likely in the upper 50s true speed.

And yes, you should be spinning the RPMs higher - say 4800+ with the prop you have.