Suggestions on new props for 336
 

On my 27 fountain going from a 23 mirage(non-plus) to a lab finished 23 mirage(non-plus) gained 300 rpm and a couple mph top end. Then changing to a 23 4 blade spinelli dropped a mile or two top end but added more out of the hole punch and mid range cruise efficiency and also reduced top rpm by a few hundred rpm.

On my new 336 Formula with 454 mag's the top rpm with 23 mirage plus props is 4700-4800 rpm.

Wanted to know who has lab finished their existing mirage props and who has switched to 4 blade props and their results. I would like to get my peak rpm to 5000 at WOT. Also interested on out of hole and mid range benefits seen from those who have switched to 4 blade.

As always many thanks for your knowledge.

On my 89' 311 SR-1, with your basic 454 Mags, I swapped from 23 inch Mirage to 24 inch Hydromotive Quad IV's and gained 7mph at cruise and 3mph at wot according to my gps. My boat is ass heavy. The Hydromotives lifted the stern out of the water a bit more, ergo less drag, and overall the boat rode more level. Exhaust noise went up to because the box was further out of the water, noticably louder, not obnoxious, just louder. The guys at Hydromotive were very patient with my questions and told me exactly what I could expect. The 7mph cruise increase was just great. Went from 47 to 53. Much quicker up on plane, effortless, and stronger midrange punch. Couldn't be happier......

Formula Outlaw- What were your cruise and WOT rpm with the 23 mirage (non plus?) and 24 hydromotives? With that change you went up quite a bit in pitch. I would have thought that you would have gone to a 22 or maybe a 23 hydromotive but would have never guessed a 24 pitch. My understanding is that a 24 hydromotive would be theoretically similar to a 26 mirage prop, not close to a 23.

As a comparison our power is the same but the weight of a 336 is much higher than a 311 which might affect my prop choice.

I'm running 23" labbed mirage (non-plus) props on my 336 with hp500's and 1.36 drives. We just got the boat last year and haven't tried any other props. One engine is in getting a refresh now, so I'll be able to do some better testing later in the spring. The Hydromotives sound like a pretty good choice.

Powerguy, you are completely correct in the theory that when you go to a four blade as opposed to a three blade, the "ratio" changes. The rule of thumb is that if your running "X" pitch three blade, then switch to a 4 blade, then you should downsize an inch or two to be equal. HOWEVER, here is what happened. Like I said, the Hydromotives are designed to add stern lift, and my boat is real ass heavy. Once up on plane, the Quad IV's lifted the stern of my boat, I'm guessing here, probably at least two inches maybe three. It was basically the same as reducing the "X" demension on drive position. Kind of like installing a set of 2 inch shorter IMCO lower cases. There is where I got such less drag, and was able to gain rpm. On boats that are not as ass heavy as mine, you would not see the same increase, it some instances it might actually cause too much lift and you could lose speed by the increase prop slippage. The guys at Hydromotive explained this VERY thoroughly to me before I decided to give the props a try. They told me if they were not real real close with their estimates,
they would fully refund me the money for their props. I noticed the difference as soon as the boat started to accelerate to pop up on plane, much quicker, much easier, not as much throttle required. Once up on plane, I could feel the boat was "freed up". Every aspect of running on plane was so much easier. Stayed on plane at lower rpms than with the Mirages. Overall, those props did exactly what Hydromotive said they would. Hope this explains what and how I gained the rpms.

With the Mirage's I was running around 4850 wot, with the Hydromotives I'm right at 5000. I use 3400/3500 as my cruise speeds, sometimes a little higher. From 3300 up to 3650 or so the speed difference stayed right at 6/7 mph. Once I got above 3700, the speed difference started to diminsh, down to about 3mph at wot.

Hope this helps. Any other questions please ask. Russ

p.s. If you call Hydromotive, ask about the new five blades........

I would guess that my 336 is as ass heavy or maybe a little more so than Formula Outlaw. It does make sense that the more boat out of the water the more speed. It sounds like a swich to a 4 blade prop is the logical step forward.

Has anyone tried Bravo 1 4 blade props on their older Formula as it is my understanding that new boats come with Bravo 1 4 blade props. I have read that the Bravo 1 prop is better out of the hole and midrange than the hydromotive for similar applications but they are cut differently so the prop sizes will be different.

I talked to Hydromotive about this, and they said that the plain Quad IV provides stern lift for rear heavy boats (similiar to a Mirage), while the Quad IV-X is very similiar to the Bravo 1 props, which provide bow lift. Bow lift is typically needed on newer stepped hull designs. According to Hydromotive, Mercury does not have an answer for boater who want stern lift in a 4 blade. I also talked to Mercury Racing labs about this, and they in a round about way said that the Bravo probably wouldn't be the best choice, but who knows, give it try they said.

Powerguy, how much does your 336 weigh? A 311 weighs 7400 dry, with most of that in the rear with engines, trannies, and drives.

I am going to try a set of Bravo's on my 311, but probably won't get a chance until late May or June sometime. I am thinking that at higher speeds, the bow may start to plow, but I'll have to wait and see myself.

Jaybird, I don't know what you are running for power, but I can assure you I don't have ANY trouble with the bow "plowing".

Just out of curosity, if your 311 is already stern heavy, (like they all are) why do you want to add more bow lift with the Bravo 1's????????

When I was running the Mirage, at WOT "Outlaw" always seems a little high in the nose. With the Quad IV's the boat rides more level, just higher out of the water. This was visually confirmed by a buddy who was running along side me. For whatever it's worth, that's my experience.

Outlaw,

I am only trying the B1's because a friend has a set to lend me, so why not? I was saying that I don't think the B1's are the right prop, but because I have access to set I am going to experiment.

I actually like what I've heard from you and the tech at Hydromotive that the Q-IV would probably work nicely. I am running about 550 hp motors in my 311.

Well that certainly makes sense. dduuuhhhhh.......
What kind of speed you get with those 550's? I'm looking to repower Outlaw in the not real real distant future. Looking for around 600 a side, naturally aspirated. Would love any suggestions. Russ