I have a cigarette cafe racer 35 ft 1987 mod.

My engine will not allow more than 4400 rpm when speeding, the engine should be good for 5500.
I can take it all the way up to 6000 when I have it in neutral.
in 4400 I get it up to 44 knots.

My question is if anyone here knows what is right propeller for my boat, or who to ask to find this out.
I think my props are too big so it wil not be able too reach the maximum rpm.

My engine is a mercruiser 7.4 ltr (454) 1996 mod (500 hp each engine)
with some modifications to the cams and weber carburetor

i belive it`s the orginale mercruiser TRS drives on it now from 1988

What pitch props do you have on there now, they should be 25s or close to that anyway.

Were these engines Dynoed at 500HP, or is this a guesstimate? My guestimate is you need some 21P or 23P props.

just checked the props and it says: mirage quicksilver 48 13245 A5 23p
3-blades

is just an gesstimate to 500hp
better to esstimate the props for 450 hp maybe?

Sounds more like 375. How far are you trimming it at top rpm?

i wil shortly try to shoot the timing in top speed so i can check if the timing is correct, the vacum on the new trigger system is not hooked up with the top because there was no vacume port on the top.
also remove the water injection to the exhaust to see how the AF ratio is.

I`m not quit sure what the timing should be at top speed, but i`m afraid is to high because of the missing vacum.

the trimming is at the lowest.

Losing a bit in translation but first
At wide open throttle you should be trimmed to approx 5-5.5 on the indicator panel. If the drives are tucked all the way in you have found your problem.
Do not remove the water from the exhaust unless you want to buy new exhaust
Just slowly bring the rpm up in neutral while watching the timing with a light.
The engine isn't making vacuum at wot so there is no need for the vacuum advance to be hooked up.
Don't rev the engine to 6000 in neutral anymore

Thanks i wil fix my sylinder to the drives and try that

Yes. What Lil Red said. Do not remove the water to the exhaust. You can cause major damage. You can easily go on-line to get details on setting the timing/advance.

On the engine side, the base engine on a 87 Cafe was a 330hp 454. The next engine (and probably the most common in a Cafe) was the 365/370 hp 454 Mag. With minor engine mods, no way to get near the 500hp mark. Probably not even near the 450hp mark, but without more details, we can't be sure. You are probably 425hp at the very best. If you have 1.5 ration TRS drives, spinning 23 pitch 3 blades should just about be right.

Unless your engines are well built with good forged internals, you probably should not be spinning them or propping them for 5500-6000 rpm. The engines may not last long. 5000 rpm would be a better goal.
To give you a comparison, my engines are bored 454 to 468 with good internals, roller top end, good cams, and supercharged with B&M 250 blowers running 5-6 lbs of boost. My engines only make about 575hp and I spin to about 5200 rpm with 27 pitch 3 blade Mirage props.

On a different subject, trimming. You may not want to go by your trim indicators, they may not be properly adjusted. Once you are on plane and running about 3500 to 4000 rpm (with trim tabs all the way up) and only going straight, start trimming up your drives slowly. Do it for a couple of seconds then let the boat settle a few seconds and keep repeating. At some point a couple of things may happen. One is the drives will start to blow out (not likely with the Mirage props) IMMEDIATELY trim down some. The most likely result is the boat will start to porpoise some (That's when the bow will start to rise up and down some). At that point, take note of where your drive indicators are (this will be the most you will ever want to trim the boat), then lower your drives maybe for 1/2 second. You should be close to having the boat and drives at the correct angle to get near your maximum RPM. Start giving more throttle until you reach top RPM. If the boat starts to porpoise again, just trim down very slightly.

The above process is very broad and generic. All boats are different, and it takes years to get the feel and experience to know how your boat should feel. Also, at max speed and drive trim, do not turn sharply. Trim down some, make the turn, then trim back up. This is not necessary for broad turns. There are probably boat driving videos you can look at on line. Reggie Fountain I think has some if you Google it.

I'm sorry if I went into too much detail, but we were not given much info, so I was trying to be as complete as possible on my description.