Alum to High-5......no difference

[Cortes100]

I'm a little confused and need help figuring this out.. I have a 2008 Searay 175, with a mercruiser 3.0L (135hp).
Elevation is at 3000 ft if that matters.
It came new with an aluminum 14.5 x 19. Engine runs good, pulls good and getting 4800WOT rpms. Really no complaints but there's always room for improvement,,,,,right?
I picked up a SS Merc High-5, 13.25 x 19 to try out.
Across the entire range, there is no noticable improvement with the H5.
*The entire rpm range, the H5 is 0.5 slower than the AL, except top end is 2.5 mph slower.
*WOT is 4800 for the AL and 4750 for the H5
*I can hold plane at lower speeds and rpm with the AL
Since the H5 is at the top of my rpm range, I'm assuming I picked the right prop?? If I lower the pitch, it will be over revving. Or are there other factors that don't allow for a lower HP engine to get the benefits of the SS H5.?
I have used my onboard tach and my GPS for my data.
If anyone can shed some light on this or point me to a good prop shop, that would be great.

 

[emilsr]

Re: Alum to High-5......no difference

When I tried out a High-5 on my 20' runabout I was just as disappointed as you. It just flat out didn't work as well as most of the props I tried...at least on my setup.

What exactly are you looking for? Top speed? Cruise efficiency? Holeshot? Generally a 3-blade prop is going to be fastest; unless you're having problems planing I'd forego the extra blades.

 

[Cortes100]

Re: Alum to High-5......no difference

the aluminum works fine, but was just looking for any overall improvements. With the H5 i thought it would pull better out of the hole. With my old boat that had an outboard, i fooled around with props and found one that made a big improvement, like a wow factor. Maybe with the new boat, the aluminum that's on there is working perfectly and it might be tough to get an overall improvement.

 

[Hairygary]

Re: Alum to High-5......no difference

Like the other poster said, what are u trying to achieve. If it is more top speed, u should have went to a 3 blade stainless. I know many people in ur situation (3.0 mercriser) and achieved the same results, slight loss in top speed, but better takeoff and holding planeing on a lower speed. Many of the people I know are wakeboarders, so they purchased the high 5 to hold plane at the desired 18-22 mph zone, so they were happy to sacrafice top speed a little. They also liked quicker planing when towing multiple tubers.

 

[rallyart]

Re: Alum to High-5......no difference

You really don't have very much power so the Hi-5's extra push may not matter. Your RPM change is normal for the extra surface area of the 5 blade at the same pitch. You might find that your hole shot improves with a ventilated prop more than with 5 blades. That would allow you to have the prop spin up faster and put your engine into a more powerful range on starts. Several shops will let you exchange a prop you've purchased, if not marked up, for another to make sure you are happy with the sale.
Stainless will usually help some with the hole shot and top speed as the material is thinner and the prop more efficient as a result.

 

[Cortes100]

Re: Alum to High-5......no difference

Top speed is not an issue, which I knew would be a couple mph lower with the H5. At the least, I figured a better holeshot, and holding plane better at lower speeds. But the aluminum does just as good. Oh well, at least i tried and found it didn't work for my application.
Thanks for your comments.

 

[180shabah]

Re: Alum to High-5......no difference

is the H5 vented???