Max5 25 vs Max5 26 vs Max5 25 ST

[Toffen]

Hi!

I hope you all are well.

I have a ol Phantom 25 with a 400R spinning a Max5 25 five blade prop to 7,060 rpms. Top speed 89 mph. I am hitting the rev limiter, so I got hold of a Max5 26 to get the rpms down and speed up. The rpm decreased to 6,900 as I expected but speed dropped to 88 mph. We discovered that the 26 could not be rised as high as the 25 pitch prop. With the 25 pitch prop we can run with the propshaft 2 inches above without any problem. With the 26 max height is 1,5 above.

A friend of mine (high perf boat builder in US) tells me that the 26 has more cup than the 25 and this creates more transomlift. And this translates to less height on my boat.

So the question is if the new Max5 25 ST with a diameter of 15,25 will be the trick. If it will give me less rpms and more speed. I can not get the engine higher. The jackplate is at the highest with the propshaft 2 inches above.

What do you think?

Cheeers, Toffen

[David]

Do you have a prop shop that can take some of the cup out of the 26? And how cold is it in Norway now?

[engineermike]

Toffen, I tried responding to your PM but your box is full so I'll respond here.

I believe Merc only casts even number Maximus props. The Max5 is cut from a Maximus casting. Any between pitches are achieved by removing cup. My understanding was that additional cup gets you more bow lift, so yours acted reverse of what I would have expected.

As for me, I ran 97.6 using an early 28" Max5. Later, I made the mistake of making multiple changes at once. I removed a hook from my hull, cut a water channel, raised the engine a bolt hole, and bought a 28" Max5 ST, which is also 1/4" larger diameter. First time out, I couldn't get over 90 mph due to excessive slip. I dropped the engine a bolt hole. I've since run 94, but honestly didn't give it a fair shot because I was heavy on fuel and stereo and didn't really make enough passes to achieve max speed. I would conclude, though, that on my boat there wasn't much if any advantage to the shorter tube and larger diameter. However, I would take my report with a grain of salt because I don't have much experience setting up or driving a boat like mine so it could skew the results.

[Toffen]

Hi !

Thanks so much ☺️ I will deliever the 26 pitch to a prop guy and see if they can do something with the cup. I consider to buy a Hill CNC 26 cleaver.. Will sleep on it ��

cheers Toffen

[Dave S]

The problem is finding anyone local to Know and How to do anything.......You in Norway must be not so full of High prefomance boat guys.... so have to get surport from our states?????? Yes my spelling sucks.........If the local prop guy can Beat......bang..... the prop as you test it .... good.....Hope he has some knowledge......I live in the USA and...... probably have a time finding a good prop guy locally.....But used props are more plenty........From your posts it looks like ya chaseing that last....mph......hard one......

[2.5-21]

Have you tried a basic Maximus prop? I know Headless Hula is running a 23 Kryptonite with a 400R and had better results with the Maximus than the Max5.
I plan to try one in the spring on a 350 Verado.

[engineermike]

I’ve tried a couple of Maximus props and liked them as all around props but the top speed suffered vs the max5. Headless hula found that his boat exhibited some nasty handling on the max5 so who knows...