I am running an hp500 with a 28p prop on a 28 Nordic heat. How many Rpm's should I be running at wot?

For a HP500 EFI merc. the wot rpm is 4800-5200rpm, its best for the engine to be running torwards the top of the rpm range at WOT.

I forgot to mention I have an XZ drive. I assume I would reach those rpms by trimming up and throwing a little tail?

Thanks for the info. I guess I made it sound like I throw a huge tail. That's not the case. I only trim up like you say, until the speed is maxed and a mild spray is coming off the drive. It's usually around 5000 rpm. As the technical motor head that I am not, I just want to be certain that I'm not abusing my toy.

What speed are you getting with you Heat?

I am not sure of the rev limiter on the 500EFI, because I turn mine to 5450 before the limiter kicks in. Either both tachs are off the same amount or the rev limiter is set higher. I do not know which. I heard the rev limiter is set at 5300, but I know my boat runs better after 5300.

With only me in the boat and less than 1/2 tank of fuel, I am seeing the speedo hit around 78-79. But of course that is a speedo. The boat handles very good at high speeds. I love it.

Thanks for the infomation. 4800-5200 is right for WAT. I thinck the rev liniter is set at 5350. I just bought a new Heat with the 525EFI.

The horsepower on the HP 500 continues to build until just before the rev limiter kicks in. For max speed the motor needs to be set up so it runs at that rpm. It's also nice to have a second prop that allows the motor to run in the 4800 - 5000 range as a cruise prop.
If you have one prop it should be tapping the rev limiter in the cooler weather so when it's hot in the niddle of the summer the motor running right where it should be.

I assume the XZ drive is made to handle those rpms without a problem. I hear it is rated for 540 hp. Does the rev limiter slow it down if the prop exits the water on occasion? Nitro...have you tried out your heat yet?