260 sonic porpising
 

hello,
new to forum,i have a sonic 260 prowler,just purchased in summer of 08,496 mag 22 bravo 1 4 blade. i have a problem with the boat porpising at all speeds but wot unless i use the trim tabs. any thoughts ideas would be greatly appricated,thanks

My old sonic did the same thing. Had to use the tabs or it would do it. I have been told there was no fix it was a design problem. I loved the boat just not real fast but rode great in rough water. Nice user name.

i guess your prowler was a 2003 did u do any performance mods i was thinking about a supercharger but was concerned about the porpising. yes nice name.

porpising
 

I do not own a sonic however have been in and owned many boats. One boat in particular had simular thing going on. My problem wound up being the drive height position. The drive was actually installed from the factory about a 1/2 inch higher than other makes. An experiment from the factory I'm pretty certain. What at least helped noticably was an intimidator 3 blade prop. It's similar to a clever type prop. At least see if you can try one before purchasing one as I would hate to see you waste the money if it didn't solve your problem.
http://www.hydromotive.com/int_3.html

Good luck and be sure and keep me posted.

John

i tried a mirage plus 23p 3 blade which helped but seemed to list the boat to the port side not sure why it would do that. i could run without tabs but could only trim drive very little before i would need to use the tabs,thanks for posting

porpising
 

Sounds like you might be on to something though. The mirage is what I noticed my problem with the most. If you are able to try an Intimidator get the 24 pitch. You'll lose a little speed at lower RPM's as your mirage however it will pull harder and probably a little more top end. They are not as efficient as a mirage.
John

i will start my search for that prop worth a try thanks

prop search
 

No problem. I hope this helps for you. Don't worry about it though just go have fun. I am not looking at your first post at the moment however does this still happen if you have your drive tucked in?
Regardless I'm certain you'll see some results with the right prop.

Take care and good luck.

John

I haven't tried it on a sonic, but sometimes a nose cone on the drive can settle down a loose boat. It turned a chine walking 25 checkmate convincer into a boat with perfect manners, and it was only a 55mph boat, which is well below the speeds nose cones are recommended for. Perhaps you can swap drives with someone for a day to try it. As you've discovered, different props can help too.

Call Brett at BBlades. He can help with the problem. You may need to try and add some lead ballast to the farthest forward compartment. I use 150# of lead in my Spectre to calm the porpoise. Maybe you could test by getting a buddy to ride up in the v-berth as far forward as possible. http://www.bblades.com/

That is a very good point that I missed also. Definately do the wight thing also. Balancing a boat is important. Plus be sure and get your best buddy up front and lock the cabin door. Been there before. Make sure you at least get him out in 3 to 4's for a few minutes anyway. :evilb:

just tell your buddy the beer is all the way up front.lol:ernaehrung004:

Stick a 1inch shorty on it and it will stop !!

not sure what the 1" shorty is
i will be ready for boating in may i am intrested in trying the weight transfer i know just the friend for the job

Whoah! Lots of chefs in the kitchen!!

Here's my recipe though!

You can try these different setups mentioned above. Some may help. Some my hurt. I wouldn't bother with a 3 blade on that boat.
I had a 1999 with an HP500EFI and ran a labbed 24B1 prop.

The notched transom is the root cause of the issue. The design of the notch is to fool the prop into thinking its on an extension box to put the prop in cleaner water for more bite and performance. However, its a finely balanced double edge sword.

As you get the boat up on plane, it naturally wants to continue to bow lift itself out of the water with the more thrust you put into the prop. As the boat continues to "rock/lift" back to the end of the hull and lift the bow, the running surface runs out of hull. This is where the notch would have been. Essentially, the boat "falls" "off plane" sorta, to where the hull right in front of the notch begins to hold the boat up again. This cycle of stretching out and then "falling" becomes known as a porpoise.

Some Sonics, depending on setup, trim, prop, fuel load, passenger loading, drive height, driver style--will porpoise; at times. The 28 was known for bad issues with this, as was some of the 35s/358s. The big boats like the 386 and up don't have this issue, but you will find it on a few of the smaller (26/28) hulls, on particular boats--depending on who monkeyed with the setup over the years trying to squeak that last .00000257881789 mph out of it.


My advice; take it or leave it:

Tuck the drive a bit. Many folks run with WAY too much trim, especially on a straight bottom boat.

Lower the tabs until the trailing edge is even with the bottom of the boat. Get extended tabs if you can to give the boat some more "hull" to run on. If you have the Bennett tabs, the extended tabs swap right in place of the 12" long ones. www.bennetttrimtabs.com


Also, you can talk to Brett at BBlades. He knows his stuff.
As does Julie and team at Throttle-Up.

The rocker bottom doesn't help either. I'm running 630 hp with 690 lbs of torque. I have a 26 B1 and a 25 revolution 4. The boats get on plan easier with the revolution prop. It also settles down pretty good at 50 mph cruse. I've called Sonic to see if they every did any R & D with a shorty. They didn't. Thats one thing I want to try this summer.

03sonic Lisen to every word in sydwayzs post!!!
I also have 260 prowler 2001. When I purchased the boat I
thought something was wrong with and to find out I didnt know how to drive it. Put the tabs down with the flat edge of the boat, and trim in a little more. Thats all it takes. Do your self a faver and leave the 4-blade on. If you still want to trim up then do it at wide open throttle. The boat can take alot of trim but you have to have it moving 50+mph. Do you have the 425ho mag? I just put a new raylar 525 in mine with cmi sport tubes.

What kind of wot speeds are you getting?
Mike

1/2 fuel,two people,all supplies and a little chop 71-72. its not a fast boat but very solid. These are heavy boats for there size
I think around 6000lbs loaded.

engine

wow some great info thanks for everyones input,sydwayz i like what u are saying great info on the hull. i will try your suggestions first and will look into larger tabs maybe k-planes?

with 2 people and full tank it will run between 64-66 mph on gps.would like to pick up some more speed but wanted to figure out tis porpising issue first.

this is my second boat my first was a 88 baja force 235 which i never touched the tabs and was able to trim the drive alot, so i guess i thought this boat would be the same. but this is a diffrent animal. on the sonic i dont trim the drive alot,not as much as i thought i would be able too.

again thanks too everyone
john

noise pollution what is the rocker bottom?

Rocker means the bottom has somewhat of a banana shape to it; front to back.

Your boat and motor looks nice. :ernaehrung004: I have the same paint and colors. My boat weighed in at 6200 lbs. Best speed 71.6

http://i448.photobucket.com/albums/q...0/DSC04566.jpg

http://i448.photobucket.com/albums/q...0/DSCF0041.jpg