Anyone moved from a dual prop to a performance single set-up??

[Maxumus]

Just curious how the boat responded, got up on plane, etc.

I started a thread recently inquiring about stronger outdrive otions for an over powered heavy boat.....LOL.....and Im considering a B-max, a Konrad, or crossing my fingers on a well prepped XR drive.....all of these being single prop applications.

Here is a link to that thread

Best Drive for high power heavy 27' application??

I have a typical cruiser deep V hull and currently run a BIII with a 2.2 ratio and a pair of 20P props (conservative ratio/prop set-up aimed at a low power BIII design).

More than doubling the power and the torque and looking into a single prop with a 1.35 or 1.5 ratio drive....

With a much more aggressively pitched four blade single prop do you guys think an 8200 pound boat will still plane reasonably quickly or will it blow out the single prop too easily? I dont mind a little slipping because that will help keep the drive in one piece but I want the boat to plane reasonably quickly and Im just not sure if that can be done in a single prop design in a boat that heavy but I hope it can!

Any input for others who have swapped from dual prop to single applications would be really welcomed!

Thanks,
Tony

[hoozeyurdaddy]

I would stay with the B 3's, yur not going to be running speeds that are to much for the B3 and it will give you the best performance for that boat, as long as you don't just hammer the throttle's down, I think they will do fine. I have made the switch the other way to help the heavies get up.

[Maxumus]

Thing is this...

Would 400 more ft/lbs of torque, higher prop speed (due to a much taller ratio drive) and a much more aggressively pitched single prop plane alot more effectively than I'm experiencing now with my current underpowered conservative drive/prop stock set-up?

I feel (speculate) it can and I don't mind the single prop slipping a bit if I get a little too aggressive with the throttle trying to plane off quickly as long as it will plane faster than my anemic stock set-up does now (really my biggest gripe with its current performance). I know that a little prop slip can potentially keep driveline parts from failing/breaking.

Bottom line.....I really need some advice from a good prop/drive expert.

The reality is few people have taken a standard cruiser and tried to up the ante in performance as much as I am attempting to but that's the shear essence of hotrodding.

I like this boat...it does what I need it to do and use it for well and I already have a fair amount of time invested in custom upgrades and amenities.....Im just looking for more performance and I don't have dreams of grandeur of trying to go 80 MPH or anything silly with it. If it could cruise at 45 MPH comfortably (low RPM) and go 60-65 WOT that would be perfect and probably bordering on all this hull might be able to handle with a reasonable amount of safety factor built in. Thing is I have a much more extensive background on the automotive side so its more difficult for me to help myself in this situation and properly plan/execute what I'm trying to do without relying on opinions from those more intimately familiar with marine performance obviously. But that still leaves the problem of not many of them having dealt with this type of application and its really a best guess kind of situation.

Anyway....I'm thinking/hoping someone somewhere has done something similar....maybe put a much more powerful engine in a fishing boat of something....LOL

If any of you guys know any really talented and informed prop/drive experts I would really appreciate if you could pass that information along.

I have time and I will continue to gather knowledge and opinions of what I am trying to accomplish. Armed with more of that should allow me to hopefully make some wise decisions this winter when I embark on the motor swap and subsequent drive/prop upgrades.

Should be an interesting project to say the least.....trying to minimize wasted money and other pitfalls as much as I can.

Thanks in advance for whatever help you may provide!

-Tony

[ACrooks69]

Stick with the B3 in your application. The dual props will be just fine if not better well into the 60's. I just went from a B3 to a B1 on my Stingray 230LX, but I went from running 57 with a 5.7EFI to a 383 with 480hp and 470 lbs/ft at the motor trying to getting into the mid to upper 70's. You will really miss the docking handling with the dual prop setup and your bow will point to the sky for a while.

[HTRDLNCN]

everything I have read says the B3 is good to 65mph
so if thats your goal you should be fine.

[Maxumus]

Originally Posted by ACrooks69

Stick with the B3 in your application. The dual props will be just fine if not better well into the 60's. I just went from a B3 to a B1 on my Stingray 230LX, but I went from running 57 with a 5.7EFI to a 383 with 480hp and 470 lbs/ft at the motor trying to getting into the mid to upper 70's. You will really miss the docking handling with the dual prop setup and your bow will point to the sky for a while.

Did you make a big change in prop aggressiveness and also drive ratio?

Also the difference you saw in torque output would be a third of the move I plan on making.

A few days ago I spoke with Brett at BBlades.....super knowledgeable and very nice guy. He says we will be able to spin a very aggressive four of five blade single prop with alot more pitch than Im currently running obviously much faster at the same engine RPM due to the much taller drive ratio (1.5 versus 2.2).

He doesnt think I will have any issues planing this boat in a hurry with the new set-up. Most people havent made the extent of the moves I plan on making and thats why its difficult to get input that closely relates.

I am curious the type of prop you switched to and how aggressive it was....also, how much different was the drive ratio with the single set-up? Ultimately how much more MPH did your top speed improve when the smoke cleared?

Thanks for chiming in....

-Tony

[Griff]

8200# single engine boat needs a Bravo 3.

[Maxumus]

Im actually thinking more about the new Konrad 760 Dual prop set-up.

Besides the engine set-back hassle that seems like it would produce the ultimate results in my application with the right pitch props. I wont run a stock BIII with this much torque.....I will turn it into a pile of junk in short order.

The new Konrad looks tempting and almost tailor made for my application (moderate performance in a heavy boat with lots of torque).....this is what Im researching currently and it looks very interesting.

I also heard of a new dual prop drive from a company called Yenmar but I dont think its rated as high....650 newton/meters versus the Konrads 1000 based on the literature I dug up on the Yenmar website. Not too much independent info out....not much of any info besides the advertising videos.

Any of you guys have some dealings with either?? They are both extremely new

-Tony

[Mbam]

Some important questions to give you an accurate answer >>

What engine do you have now? Max speed? Max RPM? How fast?

Projected power/rpm/speed?

[Mr Gadgets]

Another drive you might consider is the SCX. It is beefy and tough. With the single in that big boat, the upper gear set is going to be an issue with stock B3, even if you build a B3 XR upper.

I am not really sure how tough the B3 lower is, but if it is anything like the BlackHawk drive it spreads the load across two propshafts. I have a friend that put a Blackhawk lower on a Bmax and it lasts much longer than the stock bmax lower. So take an SCX upper and put it on the B3 lower.. you may have the best of both worlds.. Dual prop with a strong upper. Or just stay with the Stock SCX and add a spacer to get the prop height you need to make it work, and then the 5 blade prop.. Just some thoughts, no real world experience on my part, but what I have seen from people in this area..

Dick