The ole Prop/Rated Rpm thread

[Eddieclemons]

As many of you know I own a 52c with 3406e Cats. In 2018 running lite she ran a max rpm on survey of 2280/2270 and once again in 2021 running lite she turned 2275/2260 with the note of her not having the cleanest of props. In the 2021 the 300 gallon midship/forward ER tank was empty with about 400 gallons in the 1000 gallon aft tank.
I have always ran the tanks full with one engine running on mid tank and other running on the aft tank. In this condition the boat will only turn 2200ish. I clean the holding tank with tide detergent and water every year and that full tank midship reduces rpm even further. Once with when she was lite and fresh out of the slings from bottom paint she turned 2300.
I don't care about the speed, but I feel I need to take out a inch of pitch out, or run lite. Currently running 32x33 four blades.
Thanks,
Eddie

Thoughts?

 

[Captain Ralph]

Does your E series offer load data? Exhaust temps?
Tachs verified?
How are the props cupped?
I'm leaning to agree with you for taking a fat inch out, maybe a skinny 2.

 

[Eddieclemons]

100% Load, Tachs verified and those rpms are stated above, gauges are slightly lower. I don't have any current exhaust temperature data, but I can access that. Cupped data is unknown, does that show up on a prop scan? if so I have not seen that data on the report.

 

[Captain Ralph]

When you take them back to the prop shop, You can discuss the cup if any.
I like a little cup at max HP.
I would like a little more RPM if all else is well. Max ship weight to 2300RPM.
Light ship to 2350/2360RPM. Not exceeding 2400 RPM.
I don't feel you will notice much, if any speed loss, maybe better MPG and better oil lab reports.

I am a great fan of the 3406Es.
Wish I could find a set more than any other engine.

 

[madhatter1]

I reduced pitch on the 34 by one full inch because the engines are older so lightened the load. Did the same on the 46. Both boats plane easier, are lighter on their feet, and have no noticeable loss in speed.

 

[SKYCHENEY]

Cat will give you a range of optimal RPM loaded. For my Cats(different model), they told me they wanted to see 2320-2350. When we were playing with props we found a set that got me to 2370-80 and I figured that was close enough.

 

[Eddieclemons]

Cat will give you a range of optimal RPM loaded. For my Cats(different model), they told me they wanted to see 2320-2350. When we were playing with props we found a set that got me to 2370-80 and I figured that was close enough.

Was that recommendation empty or loaded with water and fuel?

 

[Briankinley2004]

Was that recommendation empty or loaded with water and fuel?

I always heard you are supposed to prop the boat to whatever load you run most of the time and with tanks full of fuel.

 

[SKYCHENEY]

They told me loaded and not to exceed 2400.

 

[worldsaway]

I also removed an inch of pitch from my props a while back and didn't notice any real loss of performance and it got my rpms back. You really should be able to get your full 2300 rpms with the boat loaded as long as the bottom and running gear are clean. Those Cats are great engines. The 52 with those Cats is the perfect combo.

 

[Cricket]

Gregory Poole set up the WOT rpm for our 3406E's at 2370, boat will turn that no matter how full the tanks are. We usually run them at 1875-1900 for cruise rpms.

 

[Eddieclemons]

Well after a discussion with General Propeller this morning they are recommending a set of 5 blade veems in 31x33 over the DQXs in my requested 32x32. Price is the same. Thoughts?

 

[SKYCHENEY]

Well after a discussion with General Propeller this morning they are recommending a set of 5 blade veems in 31x33 over the DQXs in my requested 32x32. Price is the same. Thoughts?

What is the difference in price?

 

[Eddieclemons]

What is the difference in price?

The Veems versus the DQXs legacy which are made in Michigan and not overseas. It's less than $2,000 difference. The Veems do have a of about 1,100 tariff as would the DQX 2s.
I guess I need to find out how much it would be to re-pitch my DQXs.

 

[Eddieclemons]

Both are about 10k a peice.

 

[SKYCHENEY]

What are you trying to accomplish? Just get RPM into rated range or pick up speed, or??

 

[Eddieclemons]

RPM into range and

 

[Eddieclemons]

Rpm in the range, secondary would be to improve on smoothness, and third and last would be the concern of speed

 

[jim rosenthal]

General Propeller recommended Veem Conquests for my Hatteras; I think the Conquests are their "off the rack" wheels. Four years later, they are still velvet-smooth, quite a bit more so than the Michigans which we took off. I would certainly recommend them based on my experience. (36C, series 1, Cummins 370s, 1.2 ZF gears. I think mine are 20" square, but I'd have to look them up.)

 

[cww]

Veems and DQX's are the same basic technology but the Veems are CNC machined and meet Class 1 specs right out of the box without tuning. It is a better product in the sense that you will probably notice less vibration. That said, I went with DQX's on my boat and am very happy with them.