Concept Speeds?
 

A recent post by 288sunny had some replies that got me wondering a little :readinghelp:. My 04' 30 SF with cabin has 225 Opti's and runs 59.x MPH pretty much every time out. It has seen 60.x just a handful of times. I have stock 22 pitch bravo 1's turning out and the motors are mounted in the center hole. At top speed I am right at the limiter and the times its been 60.x I was hearing some beeps.

It seems others(at least 1 - low_psi) are getting more MPH than me with what seems to be the same hull and motors. I have tried every trim and tab position there is. I have also raised the motors 1 hole with no additional speed. The bottom is clean, the props look perfect etc.

I know everyone likes to bench race....so lets hear it. How fast is your concept? A descriptions of your setup would be good to. I prefer more of a daily average speed not all stars aligned one time it happened speed. but hey ill take both.

Let the racing begin !:boat:

John

I am hitting 65 on the GPS 2000 Concept 30 w/2006 Opti 225s. Mounted on top hole with a little trim left. Spinning props out. Showtime83 has sportmaster lowers and a different bracket (higher motors) spinning props in and he is a little bit faster than me. You can squeeze more out of it with the 3 blade 23s but from what I am told it is a wild ride.

What Props do you have? Also, buy top hole do you mean the motors are mounted as low as they will go(lowest X dimension)? When I had my motors one hole higher(raised x dim.) it seems like it got a lot more prop slip, enough that while cruising 35-40 going over waves(not jumping or anything) you could hear the motors changing RPMs.

I need to take an actual measurement of my X dimension.

I am running stock 22p Bravo Props. My motors are mounted as high as they will go, they are close to surfacing. When trimmed out I would say they are right at the surface of the water.

Thanks for the info. Interesting in deed. It would seem I have more prop slip or my props aren't actually stock 22p(or should I say our stock 22p Bravo props are not the same). At 60.x mph I am hitting the limiter some, so there is no way I am getting 3-4 more MPH with this setup.

John

I've yet to hit my limiter... While in the water, that is...

Jadento, where you at the Detroit opa races? I gave a ride back to one of the drivers on my concept while low_psi towed the boat, he said he also had a 30 concept. Mine is stripped down and light, only 2 batteries, no big stereo (yet). I swapped brackets and spent a lot to time playing with it. Alot could be in the setup, what bracket you have, props.

How fast is a 30 w/300 Verados?

Probably not much faster. Verados are heavy ;-) Just kidding. I don't think there are any non-stepped 30s out ther with 300 Verados.

I was at the Detroit OPA race in 14'. I was crewing for the an SVL team. But it was not me that you talked to. I did see you guys out there on the course.

John

My buddy has a stepped 36 with 250 Verado's he said 60mph.

I had a 36' with twin 275's - 23pitch 4 blade Merc's -- ran 63mph consistently.

I had a stepped 30 with twin 300 Verados, top speed was 74 with 25 Mirages.

Hello all! I have a 97 Concept 28/30, Im running 97 t200 Evinrudes with 4 blade 19p PowerTechs. Fully trimmed, Im only getting 51.x mph at 5600 rpms. There has to be more in my setup. I dont thi,k these are the right props for my boat. Any suggestions on props to get my top speed up?

A quick google search shows the peak RPM for your motors to be 5600/5700. So it seems your at the right RPM. Do you know your gear ratio? I did another quick google search and found 1.86. If that is true and your RPM and Speed stated are correct your at 5% slip. Seems like a really low slip number. My first thought is one of the numbers I used is wrong. I do think you should be going a couple MPH faster. So long story short check your efficiency with a prop slip calculator and accurate numbers...then go from there. Another question is...Are you easily on the limiter with throttle left or is it just making it there?

The gear ratio is 1:75 and max RPM range is 5800-6400

if you calculate this on a prop calc.

Pitch: 23 - Gear: 1:75 - Eng. RPM: 6200 - Actual speed: 63mph - Slip: 18%

http://www.mercuryracing.com/prop-slip-calculator/

https://www.mercurymarine.com/en/us/...specifications

phil_p999, I am a little confused. I quoted and was replying to davlan88's question about his 1997 30' CC with twin 97 Evinrude 200's. I am not sure why you quoted my response to davlan88 in your response.

I have no doubt that your previous 36 with 275's ran 63 and your numbers add up as one would expect.

John

sorry John, I only read your reply to his quote. Regardless you are right, 5% slip is too low as you can see in my comparison.

Its a lot of tweaking to get it to 5600 and throttles are buried. Even though rpms go up, mph does not. I can get to 51mph fairly easily, no trimming, at 5000-5200 rpms. If I tweak and play, ill get my 5600, but mph stays at 51.x and thats all I get. Also, I never hit the limiter. Just doesnt seem right to gain rpm, but not mph. This is gps mph also.

Gaining RPM and no MPH is not what you want. So at 5000-5200rpm you are at 51 and trimming to get 5600rpm yields no MPH gain? There seems to be a x-dimension/CG problem or prop problem or both. The only way you gain RPM and no MPH is to increase prop slip, which is no benefit to anyone...except the gas station. Does the boat feel tight/stuck or bouncy/loose trimmed out? I am not familiar with the brand prop your running I would suggest that since you are only 50hp down from me, that you try and find/borrow a set of 20 or maybe 21 pitch Mercury Bravo 1's. Bravo 1's seem to generally be the best prop for our boats.

John

From 5000rpm to 5600rpm, I may gain 1 mph. 51.x though is all I get. 49/50/51 mph and 5200 rpm is obtained fairly easily. 5600 rpms is working trim, tabs, all while controlling porpoising. Once I get my 5600 rpms, mph never goes up. I dont know what x dimension or CG is.....

I was thinking more along the lines of a 3 blade 20/21p prop, but then again I dont really know anything about prop voodoo which is why Im here. The boat feels stuck, almost like it never frees up and is straining to get that 5600rpm number. Bow never really lifts like Id expect and as with all Concepts, porpoising.

If the boat feels stuck or your not getting the lift you need now, I would not go to a 3 blade. I suggest you find a set of 20" or 21" Bravo 1's and see what happens.

John

I dont mind dropping a grand on a new set of props, but if they dont work it seems to always be a hassle returning them.

Never used it, but seems like a fit for your problem.

BBlades Test Program

John

I read through their contract and I guess what is left up to interpretation is whether the props work or not. They dont say if youre satisfied theyll charge you for the props. Kind of leaves it open to their interpretation of whether the props work or not. Also, theres a 15 day turn around time ship time included and then a $10 per prop per day fee, tester pays shipping both ways, plus $100 to test. All fees do not go toward purchase.

I wonder if having my PT 4 blades worked over to a 20p might be the route.

http://bblades.com/shipping-props-to-bblades/

Fill this form out and they will point you in the right direction. I did this with my last cat I had and it worked wonders. (saved a lot of F'in around, time & money) make sure you scroll the entire page, it's not just a shipping form......


Phil

Bottom line is you have to experiment with props and check your drive height, you gotta have some prop shops around Tampa that will let you try a Mirage or Bravo prop.

I have a nice pair of 21P Mirage if your interested in starting your experiment, $550 shipped to Tampa!

Pete280 - are they Mirage or Mirage Plus? Also, would you sell just the LH rotation prop?

There plus but I dont really want to sell one, i am really looking to trade for some 19 Mirage plus,

My buddy has a 2010 27' w 250 verado flashed runs 63. Runs a 22 pitch bravo fs