37 Active Thunder Prop tweaking time.
 

I lost a blade on the LH 28P B1 on my boat this weekend. Damaged the lower casing as well when it came off. Case in the process of being replaced as we speak, including full checkout of the lower, gears, and bearings.

I was running 28P B1 4 blades bone stock.
37' Active Thunder
Single step
496HOs (425 HP)
Bravo 1 XZ 1.50 drives
Spinning about 4800 rpms when light on fuel and friends, occasionally make it to 5000 rpms trimming out with right conditions
Approximately 9800 lbs dry (with stereo and 4 batteries)
180 gallons of fuel, so
10600 lbs or so with half tanks a couple folks, and gear
Props only recommended to spin out per Active Thunder
I pulled 74 mph gps with a little chop this past weekend with above setup at about 4800 rpm.

Best I have EVER seen the boat do is 77.5 mph gps. That's in 3 foot perfect rollers in salt water.
Smooth water will get it to about 71 mph or so.

I now have excuse and reason to do some prop tweaking. I am looking for a pair of 28 B1 props, or a LH 28 B1 prop to replace the one that broke. I would like to have them matched and labbed/perfected, BUT NOT THINNED OR TOO SHARP, as I boat in the Potomac River which has a section of falls up north in the mountains which creates a LOT of river derbris. I don't want fragile props.

I would like to get the boat to see 80 mph legitimately when I get that perfect water again, just once, but propping the boat to see 80 mph is NOT my main concern.

What is my best option/choice?

28P B1 4 blades bone stock? (Was I at my best prop choice already?)
28P B1 4 blades trued up matched with a blueprint but not thinned?
30P B1 4 blades trued up matched with a blueprint but not thinned? (3 other same local boats with 500+ HP each side are all running best with 32P B1 4 blades or close to that, would 30P be too tall for my boat?)

Throttle-up/Matt & Julie, what EXACTLY did you do to Craig Hall's (Craig223) 28P B1 props for his Cigarette Bullet? I have not asked him yet if I can borrow them, but would that pair be something I should try if he allows me to do so?

Re: 37 Active Thunder Prop tweaking time.
 

You have mentioned turning the motors at 4800 as most common. This being done with a "standard" load. With that being said, the 28P bravo 1 Lab Finished would be my favorite choice. We would follow our standard thickness curve. It will not compromise the integrity of the propeller as would a thin specialty curve.

With your current slip % of 10.54 (figured against the last time out #'s), you will only get to 78.63 theoretical mph. Of course different loads will affect the outcome.

This selection would give you good all around performance.

You also mentioned 5500 rpm abilities at certain times. This is a little confusing since the rev limiter should of kicked in around 5150rpm.

Another option, for speed specifically, would be to run Lab Finished 30P bravo 1's light loaded. With the appropriate weight and water you would be able to reach your 80mph goal. You will also improve your cruise speed. You will sacrifice some throttle response, especially with heavier loads.

Re: 37 Active Thunder Prop tweaking time.
 

Brett, thank you so much. The rev limiter is the stock 5150. I believe I only mentioned 5000 rpm above as with a very light load with a lot of air under the boat.

Re: 37 Active Thunder Prop tweaking time.
 

Hello Brain,

Sorry to hear about your prop! Using the numbers above at 4800 RPM at 71 MPH, I assume that this is your "all day long" speed, then your slip is at 14%. This is in line for a 4B propeller. However I have been working a lot of 37 Active Thunders in Texas as of recent and they have all been running Bravo I propellers. I sent some Hydro P5-X test props to them and all 4 of them are now running the P5-X propellers with there Bravo I props as back-ups. I would suspect that in your case you would experience the same speed if not a 1 MPH increase with them due to there increased efficiency. But more importantly they have experienced increased hole shot, increased accleration, increased cruise speeds and maintining there top end within 1 MPH either way. Just food for thought.

If you need a Bravo I matched to your RH propeller we can utilize our computer for an exact match.

Julie

Re: 37 Active Thunder Prop tweaking time.
 

Thanks Julie. I had a talk with Craig Hall today. I am going to give his props a shot as soon as I strap my lower back on hopefully at the end of this week. According to him, Matt took a shave off the diameter, and took them down to around 27P. This would take me to my rev limiter, and hopefully be just as efficient.

How much would Hydro P5s cost me? I have a line on a pair of Used B1 28P for less than $500 which is a good deal. Again, gaining a little tiny bit here or there is not my main concern, but the P5 does sound enticing. Perhaps if I pick up Craig's props from him, and they perform well, they could be a nice all around prop, and a pair of P5s setup right can get my my 80mph once in a while.

Re: 37 Active Thunder Prop tweaking time.
 

Brian,

How did you loose a blade? I know the Potomac is rough on props! The P5 Hydromotives would probably be a great for your boat. But you might want to reserve them for Anna or SML as they are more expensive. I think the labbed 28 B1's will work well. You just need some more rpm.

Damn I wish I was there to help you prop test!

Eric