I've got a 2003 TZX190 with a 150 VMAX carb that I'm struggling to get more speed out of and I think it's due to low RPMs. The motor runs great and I've gone through the carbs by cleaning them out. I've also replaced bad needles, gaskets, etc. The motor runs great, no lean sneezes or dying at idle. Compression is good and consistent across all cylinders. I think the issue is either the prop, hotfoot, or height of the jack plate.

I'm currently only able to get up to about 4800RPMs with the hotfoot that came with the boat. I trim up to the point my water pressure gauge reads between 15-20 PSI. For some reason I cannot get more RPMs out of the boat.

I'm thinking either the issue is my hotfoot depressed all the way forward isn't actually moving the throttle cable to it's fullest position, prop isn't right, or jack plate isn't in the correct position. The prop is a 23M that I believe came standard with this motor.

Anyone have any advice on where to start? Measure prop to pad and check throttle cable if it's being fully extended when the hot foot is depressed?

Keep trimming up until your speed drops.

I have the same boat as you. My setup has a 25M prop. I get about 5500-5700rpm with a top speed of 60mph (just me, gear, and 1/2 full fuel tanks). You may not be trimming high enough. On my boat, there is a lot more trim available after the last tick on the "up" side of the trim gauge, and I still have 10-15psi of water pressure. Follow what Chris B noted.

The other things you mentioned like the hot foot are also possible, but try what Chris B said first.

I may just be a wuss. I trim until the spray is directly behind my seat.

Don’t look at the trim gauge, water pressure gauge or spray. Just keep adding trim until you see about 57-58 mph.

Keep trimming up while running WFO ... make mental note at which point the boat does a 360 and don't go past that point in the future.

I'll give this a try the next time I'm out on a calm day!

Well. Hmmm.

My TZX190 with the Yamaha F150 (both 2004) would just bounce 60 measured through GPS with just me and a light load. 56-57 with two people and loaded boat and live wells. The boat has a 12” slidemaster plate and a reliance 21 prop. I’m not sure what the RPMs are currently as the tach was never really accurate. It showed 6800 rpm pretty consistently. The prop to pad was 2-1/4”. And the boat has two power poles and a heavy Ultrex on it.

Maybe you are turning too stiff of a prop? Maybe the gear ratio is different than my 4-stroke was. I say was because it grenaded a week and a half ago. Maybe 6800 was accurate.

I bought a new 200 SHO….just gotta get it installed now. That motor will have a T2 25 or 26. Should be good for mid 70’s when it’s done.

What is Prop to pad on the set up? I dont have the same boat but when I first got my boat, it was motor to transom. Prop to pad was 4.5". Once I put a JP on it and set it at 3.5", I saw a huge increase in RPM and speed. Went from a 45 mph boat to a 52 mph boat with a 150 hp. Elevation kills me though and I have to prop way down to even get on plane here. But played with a few things here and there and I am touching 56-58 with just me, gear and a half tank of fuel.

can you film a video of this?

Prop to pad is 3.75 inches. I think I'm just not trimming enough...

I’m pretty sure the rev limiter is like 6000/6100. As stated above, trim up and keep an eye on water pressure. You may need to try a lower pitch prop.