what hp am I pushing out of this 540
 

88 240 sport labbed 26 bravo 74 @5600 18 slip. 28 stock bravo 5000 72mph 19 slip motor is a 540. 587 600 cam not sure of duratin 1.5 drive stock depth and length how can I loose some slip and gain mph planes very easily thanks

Is your mph on gps or a water driven speedo,, Horsepower depends a lot on your compression, heads, intake, exhaust, carb. size & jets, timing , 87 or 93 octane gas, I would guess 475 to 500, or close to it, if the mph is on a gps.

It is on gps the heads are ported square ports cam is a 587 613 lift not sure of the duration 1050 dominator and about 9.5 to 1 but im actually more worried about the slip numbers and the lack of stability because the motor im building is going to be much more 315 afr and a cam from bob but no need to do that if I cant get the hull under control

My 240 sport went 75 all day every day with a 496 GM rectangle port heads little bit of piston and a less than optimal cam.

Is the bottom of the hill warped?
Something wrong with the lower unit case?
Are you sure it isn't water logged?

Have you checked the drive ratio? Maybe it isn't slipping and you just have a turd of a motor.

what year 240 did you have

Have you tired any 3 blade mirage props? maybe a 23 plus or 25p

I was wondering the same i'm running a stock 502 in a 2001 26ZX Donzi and runing 68 on GPS with a full load of fuel at 5000 and a stock Mirage 24, I can run low 70's just getting low on fuel... Just doesn't sound right for a 540

I did have a 23 plus on and it would spin 6200 at 71 I would like to try a 27 plus mirage

Also the donzi is prob a more efficient hull

His year of 240 is the same as 24 Outlaw.

365hp=60mph
425hp=65mph
500hp=70mph

These are all pretty close speeds on a 24 OL with the listed HP. I would guess your 540 is about 550-570hp.
Your cam is probably a Crane 139011 which is a little small for a 540.
Ideal prop would most likely be a custom labbed Bravo 26.