orthos1

I have a 25 talon cat. Powered by a Mercracing efi525, Imco 1.5 drive and I am trying to figure out the prop. Right now I have a 32 Spinelli and a 28 bravo 1. My numbers figure out that a 30 bravo 1 if the prop. The 28 has been labbed by Merc.

I still have the CMI headers 2007 edition checked for leaks = none. I know of the problems with the CMI merc spec headers but the only ones I would replace them with are 7 k Stellings.

Any help with the props? Try the ones I have then see? On the CMI headers get rid of them and buy new Stellings?

hoozeyurdaddy

what kind of #'s are you getting now with thoughs props?
as far as headers, get a new set of cmi's half the money.

orthos1

I just re-powered so I have no numbers. With the spinelli and the previous 870 hp blown 510 I was getting 126mph on gps. I had to slow down due to my back and neck injuries, So I put a reliable 525 in it and popped the valve first start. I think you are right get the new cmi headers replacing the old merc spec cmis that came with the engine.

My calc say 30 pitch if so I may have the spinelli de cupped.

fireboatpilot

Put a prop on it and run it. See what rpms you get out of it. If you max out on rpms at half throttle then you need more prop. On the other hand if you are at WOT and can only get 4000 rpms out of it you have too much prop. Figure about 200-300 rpm change for each step up or down in pitch. I don't think you'll be able to figure it out on paper and hit it right the first time without testing. Too many variables even on very similar hulls.