I have a friend with a 2006 28 heat with a 496HO & bravo drive. It is a MCOB and does not have trim tabs. Right now he can spin a 24P bravo one 4 blade up to 4800rpm around 55mph. Does this seem right to you guys? Not sure on his X dimension but I am assuming its at the factory setting. Any feedback would be great as I see most of these boats should be able to hit 60-65mph. I know lacking the tabs is not helping.

Rookie question but how to tabs help increase speed? I always pull them all the way up when trying to gain speed and use the trim to get the hull out of the water?

The stock rev limiter on a HO is 5150, so the rpm gauge is way off, as is the stock speedo, check speed with a GPS, I'm sure its faster than 55 unless there's a prob with the motor, a 24 bravo is usually the correct prop in these, some run a labbed 26, also those years usually require a 1" spacer to improve traction and pick up speed, also on the drive, just above the low water pickup is a small hole where the water flows into dream-o-meter, if there's debris in there your speed will read way low, usually they are about 5 mph fast

My bad he is turning 4800 not 5800. 55mph was using a gps the last time out. I know the boat does not have a 1" drive spacer. Engine seems to run good, start, idle, get on plane, accelerate etc....Engine has less than 200 hours. Could it be a possible issue with the throttle linkage?

Wouldn't hurt to check for wot, do you have access to a merc scan tool? That's the easiest way to eliminate any motor issues, but if it sounds healthy and is getting full rpm it should be fine, how's the prop look? Is it a stock 24 or has it been lab bed? Rpm's are within specs but I've always propped for 5100 in spring and fall that puts you around 5k in summer, which is where the HO makes max power

Prop appears to be stock. I will have him get a scan on the engine and will have a Merc tech check the throttle cable.

Something is off I have the same boat 2007 prop is 24 bravo copy ( hammer ) does 63 mph on gps . This was with 5 people and lots of fuel in the boat on the ohio river.RPM are around 5100 rpm at max. Had a 26 bravo on it when I bought it but that was too much prop for the 496ho in this boat. I only turned 4800rpms with that but never gps the speed.

Agree, my old Heat ran 62 consistently with a tweaked 24 (sharpening, balanced). Something's off for sure.