Propping a B3
 

I know I don't have a speed boat by any means but want some advice on proping a b3. Have a 23 foot boat, 496 mag 375hp, b3 1.81 drive with stock 26 props. Manufacturer states boat should run 60.8 mph with this setup. Have only been able to get 56.5 at wot of around 4300. Hull is clean and has all new plugs and filters. Boat weighs in at close to 4500. I believe a set of 24 props is the way to go. Hard to find a set to borrow and don't want to buy a set that aren't right. Sound like I'm going to be ok?

Pol83x,

24's will take you to 4700 and the engine will like this. Your acceleration will improve but top send will stay about the same. You may see a 1mph increase. This is the way to go in my opinion.
Manufacturers always test boats with low fuel and extreme minimum gear. So, the numbers tend to be best case scenarios.

Brett

Thank you for the reply. Any thoughts on the 4-3 setup or Signature 4x4's?

If you want low end grunt move to the 4x3 or 4x4's. I personally like the 3x3 sets because there is more adjustments and tweeks that can be done to them.
The 3x3 sets are typically the faster set up especially when slip % is low to begin with. Mercury created the 4x3 in the early 2000's as a fix for cavitation burn when mounting B3's to high HP applications. In a effort to decrease inventory costs and as a way push sales on the newer technology, the current 3x3 B3's will be discontinued.
I'm not happy with that decision.

Brett

Thanks I'm now on the hunt for a set of 3x3

Quick update. Picked up a set of 24p 3 blades that were just checked and polished for a steal, now just got to wait till spring. Only thing I can do with them now is make a big ol mixed drink.

Awesome. Let us know how they work.

Brett

My '04 Chap 260 SSi with 496 MAG/Bravo III 2.0:1, 26" 3 x 3 prop set ran a best of just shy of 54 MPH GPS. Most days it was a 50 - 52 MPH boat. I don't see your boat doing 60 MPH but 58 should be doable. Update us in the spring. BTW, from my own personal experience Chap hulls do not like the 4 x 3 prop sets at WOT. Cruise they are great but they lift the stern too much on the big end and feel skittish.

Mercury created the 4x3 in the early 2000's as a fix for cavitation burn when mounting B3's to high HP applications.

Brett[/QUOTE]

So this is why I'm cracking and blowing out pieces of rear props within 30 hrs?......
22,000 lbs 640hp @ 5200/ 690ftlbs @ 4100 2:1 drives 28 p....maybe a candidate for the 4x3??

Potentially, yes.
Can you post some photos or send to [email protected]

Brett

I had a 02 265 ssi with that setup, could hit 54.8 on its best day. I'm hoping for 58 on my 230ssi.

So this is why I'm cracking and blowing out pieces of rear props within 30 hrs?......
22,000 lbs 640hp @ 5200/ 690ftlbs @ 4100 2:1 drives 28 p....maybe a candidate for the 4x3??[/QUOTE]These came out around '05 to address your issues.

I talked to merc racing on those xr props. They told me they are intended for use on large cruisers and would be no good for smaller runabouts and sport boats.

Have to agree, your boat doesn't weight enough for a 4 blade, your slip right now is only 7.7% and that's good, I'd love to have that little slip.

They are superior to my stock (well, slightly BBlades modified) 3 x 3 set in terms of hole shot and cruise efficiency. I picked up 2 MPH at my normal cruise RPM (3,400) over the 3 x 3's. On the big end I obviously cannot pull as many RPM (26" 3x3's vs. 25" XR's) and I cannot carry the bow as well as I can with the 3 x 3's. Overall, for most of the boating I do the XR's are my preferred propset.

Is there any functional difference between the XR's and the standard 4 x 3 prop set? ....other than polish of course.

The XR props have a lot more cup Merc told me. They said would be a waste on my boat.

My interest in the B3 has been rekindled since I swapped one on from my other boat just to see how I liked it. Truthfully, I think I like it 95% of the time over the B1. With the B3, it planes quicker with minimal bow rise, higher cruise speed/rpms, way less load sensitive, better low speed handling, noticeable fuel efficiency improvement AND ODDLY ENOUGH, a better ride in heavy chop. The only downside from my B1/B1 prop setup has been looser and less confident handling at higher speeds. The B1 really hooks up the back end on my boat , but carries the bow slightly less and really has confident handling.The B3 seems to lift the transom (my theory for the softer ride) AND carry the bow higher even with little trim. I don't really notice any difference in top speed as I only have a stock 502 Mag, so my top speed was only mid 60's anyway where the B3 starts hitting the wall. If possible, I would like to find a B3 combo that lifts the transom SLIGHTLY less and carries the bow SLIGHTLY less. Would any of the 4 x 3 sets offer this?

My interest in the B3 has been rekindled since I swapped one on from my other boat just to see how I liked it. Truthfully, I think I like it 95% of the time over the B1. With the B3 (3 X 3), it planes quicker with minimal bow rise, higher cruise speed/rpms, way less load sensitive, better low speed handling, noticeable fuel efficiency improvement AND ODDLY ENOUGH, a better ride in heavy chop. The only downside going from my B1/B1 prop setup to the B3 has been looser and less confident handling at higher speeds. The B1 really hooks up the back end on my boat , but carries the bow slightly less and has really confident handling.The B3 seems to lift the transom (my theory for the softer ride) AND carry the bow higher even with little trim...again, loosey- goosey handling at 50+. I don't really notice any difference in top speed as I only have a stock 502 Mag, so my top speed was only mid 60's anyway where the B3 starts hitting the wall. If possible, I would like to find a B3 combo that lifts the transom SLIGHTLY less and carries the bow SLIGHTLY less. Would any of the 4 x 3 sets offer this?

disregard post #18. Its not allowing me to delete for some reason.

Many say the B3 hits a wall at 50 to 60, but there are also others here they have proof that this isn't the case and head on up above 80. Agree B3 provides more lift and this can be an issue but can also have some props designed to limit the issues if they are the problem

Blade design is different as well. Not the old elephant style ears on the XR's.

Just an update, tried the new props, boat responds very well and will now rev to 4900 rpm but I did loose approx 2 mph. Not a big deal as I am happy that the throttle response and time to plane are much better now. Probably the best set would be a set of 25's. Not sure they make a set though.

Thanks for the update - we have a 226 Cobalt with 7.4MPI spinning 26 pitch with a 1:50 ration. This weekend relatively calm water 20 gallons of fuel and just me (weighing in at 215 lbs) on GPS did 62 mph. It was warm out and I know when we have cool temps I get a little more speed.

Take care and safe boating

3pointstar

Update on my prop tuning and a huge thanks to Brett at Bblades!
Brett "fixed" my props over the winter and finally got a chance to run the boat, used to cruise at 41-42 @ 4100 rpm with two adults and some gear, would spin props hard getting on plane- had to feather the throttle to keep from over revving.

Yesterday with 8 adults, full fuel, gear and some water in the tanks....acceleration from dead stop can best be described as linear, props are totally hooked up- no blow out, cruise speed was 47 mph at 4050 rpm, felt like there was more stern lift, boat rode better than ever with all that weight aboard.

I did add new exhaust so that probably helped in the HP department; nevertheless prop work is amazing! thanks again Brett 100% satisfied

Thanks Sonic.
We appreciate you sharing the results and thank you for your business.

Brett