Prop pitch vs diameter. Surprising test results! Thanks Bob and Josh

[skav]

I've been trying to find the right prop for my 270 since I bought it a few years ago. Bravo I's sucked big for me. They would blow out bad getting on plane and also in turns at slow speed. I tried a P5X, and that was ok, but slipped a lot. Next I tried CE 5 blade 30p, which worked well. The CE 30p came out great, and held nicely in turns. I also tried a CE 28p 5 blade that worked for crap. The CE 28p kept the nose buried and blew out a lot.

I also have a 30p Maximus 15" diameter. This ran very similar to the CE, but cruised a about 3-4mph slower. My main complaint all along has been that the boat runs wet, and wouldn't carry the bow.

Last week I dropped the boat off at TCM and asked for help figuring it out. Josh said to run a Maximus, but I told him I didn't notice a difference between it and the other props I've tried. He then told me to leave it with him and they would work it out.

Bob ended up taking it to the lake, and ran it first with the CE 28. He said it was terrible! He then grabbed a Maximus 30p 15 1/4" dia and ran that. Way better, he said, but He wanted a bit more RPM on top. He headed back to the shop and grabbed a Maximus 28p 15 1/4". After running the 28p, He came back with a smile and said that's the one. He said cruise went up 10mph and top speed improved by 4mph with 200rpm more on top.

We were at Mohave last weekend and I can back up his results. It now comes on plane quicker, pulls tubes better and idles slower in the no wake too. Before my no wake/idle speed was about 10mph because of the big prop and 1.50 lower. Now I'm at 7mph.

The the best thing about this new prop is that it carries the bow much better. I can actually get it to chine a bit if I trim up top. Before, the trim didn't do much if anything past 50-55mph. It just planted the nose and pushed water.

I am still surprised how much of a difference a 1/4" makes. I would have argued that a 28p wouldn't work, based on past experience, but this is my favorite prop now.

Has anyone else had similar results?

Thanks again Bob, Josh and the whole TCM team!

 

[Outdrive1]

Interesting. I think my Maximus props on my Eliminator were cut down and purchased from Teague. How do they know when to cut them down or not? What does the diameter actually affect?

There are so many variables with props. It's good to hear you found something that made a difference.

 

[skav]

Interesting. I think my Maximus props on my Eliminator were cut down and purchased from Teague. How do they know when to cut them down or not? What does the diameter actually affect?

There are so many variables with props. It's good to hear you found something that made a difference.

I'm not sure how you know when to cut them down. I would not have thought of going bigger than what I had. I was struggling with the idea of going smaller for better cruise and better top end, but it worked!

They did cut off the diffuser ring, but diameter is 15 1/4".

 

[HALLETT BOY]

I had Bryan up at valley propeller in Ventura do work on my Maximus , I would tell him what needed and he did a little
at a time until it now works great ! We ended up cutting it down twice and originally removed the diffuser ring , it now too ,
is my favorite prop ! Of course , I may have to start all over again when I pick up my boat next week and try out the new SCX drive .
I think the SCX lower is slightly wider than the SC to accommodate the bigger gears and bearings .

 

[ka0tyk]

i have absolutely no idea what prop i should run. im running an alpha one 1.62 on a 7.4 bbc. 21 cruiser.

glad you had success. what exactly do you feel when it slips, or "carries the bow" etc? how will i know when i found a good one? at 200-600 a piece it sounds like you have quite the collection of props.

 

[skav]

i have absolutely no idea what prop i should run. im running an alpha one 1.62 on a 7.4 bbc. 21 cruiser.

glad you had success. what exactly do you feel when it slips, or "carries the bow" etc? how will i know when i found a good one? at 200-600 a piece it sounds like you have quite the collection of props.

For me, the motor would rev, but speed didn't increase at the same rate. I notice that the bow rides higher, and the water comes off the keel further back. I do have a few in the garage. At least their shiny

 

[dp85tona]

when it comes to props there are so many things you (or a shop) can do to them to make very minimal changes are drastically large ones. I was running a 28p bravo 1 4 blade on my DCB Mach 22 with 300 pro max, it would pull great until late summer with the heat and humidity rising, I purchased a 26 bravo 1 4-blade. I sent it to R&R prop Shop in Henderson ,nv and through a phone call or two he had me set up exactly what I needed, favorite prop yet. he took a bit off the blade, and then added a bit of cup, bow lift, to help me get on plane he added a little to the diameter of the exhaust center and kinda made it flare out. this helped me drop the bow over when getting on plane by lifting the transom up.

needless to say, if you get a prop shop and explain to them what your wanting to do they should know what can be done with your specific set up.

 

[mjc]

Props = Black magic

 

[STV_Keith]

While diameter and pitch are two big components, there is a lot more going on than just that. Cup, skew, blade area, rake and a ton of other stuff can make one prop work and another of the same pitch and diameter suck. Best thing to do is pick your favorite and call a prop guy and tell him what it still doesn't do as good as you like. I use Kevin @ R&R Prop Shop in Henderson, like dp85tona mentioned. 702-564-7502.

 

[ToMorrow44]

I've been trying to find the right prop for my 270 since I bought it a few years ago. Bravo I's sucked big for me. They would blow out bad getting on plane and also in turns at slow speed. I tried a P5X, and that was ok, but slipped a lot. Next I tried CE 5 blade 30p, which worked well. I also tried a CE 28p 5 blade that worked for crap. This kept the nose buried and blew out a lot. This came out great, and held nicely in turns. I also have a 30p Maximus 15" diameter. This ran very similar to the CE, but cruised a about 3-4mph slower. I main complaint all along has been that the boat runs wet, and wouldn't carry the bow.

Last week I dropped the boat off at TCM and asked for help figuring it out. Josh said to run a Maximus, but I told him I didn't notice a difference between it and the other props I've tried. Josh told me to leave it with him and they would work it out. Bob ended up taking it to the lake, and ran it first with the CE 28. He said it was terrible! He then grabbed a Maximus 30p 15 1/4" dia and ran that. Way better, but He wanted a bit more RPM on top. He headed back to the shop and grabbed a Maximus 28p 15 1/4". After running the 28p, He came back with a smile and said that's the one. He said cruise went up 10mph and top speed improved by 4mph with 200rpm more on top.

We were at Mohave last weekend and I can back up his results. It comes on plane quicker, pulls tubes and idles in the no wake better too. Before my no wake/idle speed was about 10mph because of the big prop and 1.50 lower. Now I'm at 7mph. The other thing about this new prop is that it carries the bow much better. I can actually get it to chine a bit if I trim up top. Before, the trim didn't do much.

I am still surprised how much of a difference 1/4" makes. I would have argued that a 28p wouldn't work, based on past experience, but this is my favorite prop now.

Has anyone else had similar results?

Thanks again Bob and Josh!

Pretty sure I tested that same prop from them a few years back...or at least it was the same setup with the diffuser cut off. Those Maximus' act like a bigger prop so the 28 is kind of deceiving, it acts more like a 30-32 Bravo in terms of RPM. My cruise speed also did well with that prop and the best thing I noticed was how effortless my boat got on plane with it, it was awesome. Everyone at TCM is always top notch, glad they got you all hooked up!

 

[skav]

I came across this thread today as I was looking through some of my old posts, so I thought I'd update the thread with more test info.

I ran in MB last Nov with the new prop, and was again surprised/shocked at how much better the boat felt. It got on top of the water, and carried the bow great. While in the PR, I noticed that boost was lower than it had been in the past. Before, I would see 10psi when running hard. With the new prop, I saw 6psi at most, but ran 5-6mph faster on top with about 200rpm more than before. Water and oil temps are all down too. This tells me that hull is running more efficient and the motor is happier.

 

[HBCraig]

LIke Keith said. Diameter, pitch, cup, etc all come into play. I have a stock 26P bravo on my Ultra 247 and a cut down 28P that is labbed, the diameter is cut down a 1/2" and I had the cup taken out. It works great. I almost spin it at the limiter in the fall and spring. When it gets hot, I cant.

The stock Bravo's are nice, but when you are looking at running a top number, prop work is the cheapest way to pick up some extra MPH.

 

[BigSteve]

While diameter and pitch are two big components, there is a lot more going on than just that. Cup, skew, blade area, rake and a ton of other stuff can make one prop work and another of the same pitch and diameter suck. Best thing to do is pick your favorite and call a prop guy and tell him what it still doesn't do as good as you like. I use Kevin @ R&R Prop Shop in Henderson, like dp85tona mentioned. 702-564-7502.

That's some good info STV Keith

Working with good people is key, in getting the most from your set up

 

[BigSteve]

i have absolutely no idea what prop i should run. im running an alpha one 1.62 on a 7.4 bbc. 21 cruiser.

glad you had success. what exactly do you feel when it slips, or "carries the bow" etc? how will i know when i found a good one? at 200-600 a piece it sounds like you have quite the collection of props.

It sure would be interested if the new Mercury Pro Max would work out on your set up

They are a 4 blade over/under thru hub design with a racing blade , to be faster than a bravo and carry the nose on the larger, heavier, high powered outboard boats

Our testing shows a 6% slip reduction over a Bravo

The ones we have tested out of the box non lab'ed, they worked as well if not better than any of a dozen custom props we run in our race program.

Bravo's are a great starting point

Mercury makes a bigger prop when needed

And offers one a bit smaller to fill a gap you might fit in