im MartinB

I am going to add to my lower lifting strakes this week and I thought I would see if anyone has done this to a 31 sonic before? I was planning to start with 12" and see how the boat likes it. It's not a terrible amount of work but if someone has done it and already spent a little time it would be great information.

Rookie

iTrader: (4)

I don't believe you will notice any difference with adding 12". I added 52" to my Panther going 12" at a time and then testing. That's a lot of work for only 12".

JaniH

Did you gain anything with the 52"? Been considering this to my 26 stinger.

Rookie

iTrader: (4)

Yes, the boat handling characteristics improved and the balance is better. My Panther was a good boat in rough water, but it immensely helped the angle of attack. Less trim and carries the bow better.

JaniH

How the boat rides? what are you trying to fix? I always get excited whe i see someone trying to get improvements by blueprinting the hull, instead of adding power. Not a good comparison, but years ago i had small 22 ft chris craft hull with approx 400hp 383cid, that had too much transom lift, i shortened the lower lifting strakes 3ft starting from the transom, this improved the bow lift without any il effects. Now i have problems with 26ft stinger, twin sbc converted to single bbc wich is porpoising at wot, so something needs to be done.

JaniH

Single or twin engine? my 26ft single with rised X is porpoising at wot, only at wot.

Rookie

iTrader: (4)

30' twin. I wouldn't be playing around with strakes. I'd try different style of props and drive spacers before adding strake length. My boat loosened up.

im MartinB

Well I've blue printed a lot of boats over the years, mostly boats running 80+ mph. My boat was running 86 when I did the blue print.. and gained a whopping 1mph or probably a little less. I went back through my pile of cut strakes that I've collected over the past 30 or so years and realized that almost all the blue printing with the good gains were on stepped bottom boats. The one exception was a 32 Active Thunder and on that boat we cut off 18" of the strakes and he gained almost 6 mph. I couldn't find anyone out there with any info on the 31 SS so I didn't want to cut them off, even though I can put them back on, but I hate putting them back on it takes so much more time. This boat has a serious brake pedal and I'm struggling to find out how to release it a little. I've switched every damn part in the engine compartment to aluminum and then got rid of the slid out filler cushion to keep things balanced.. that gain was damn near 0. I'm pretty darn determined to get to 90 NA, but I'm running out of options. As near as I can tell I need to either notch the transom... BIG job and no way to know for sure. Cut the strakes easy job but if it's bad it takes longer to put them back. I'm gonna do a temporary strake extension on the lower strakes.. I don't think to the transom would be good because the would def add a lot of transom lift.. This boat stays really hooked up and nothing I've done thus far has had any negative effects so I think I just need to keep trying. One thing I find interesting is the high slip with Bravo ones, usually 22% and yet in the rough water I stay hooked up unless I'm in the air... Running alongside a friends 38 Sonic I can hear his drives breaking loose quite a bit and he runs with lower slip numbers... and same props. His boat has the notched transom.

im MartinB

I've never had this issue at wot on a boat before... On my 26 Sonic that I had for a while it would bounce if you trimmed to soon. As soon as you got on the throttle though it went away or put the drive back down. My guess is if you added 500lbs to the bilge the problem would go away... so you need to get ride of some transom lift somehow. I'd be trying 3 4 and 5 blade props first because it's so much easier. I fixed a horrible 280 Velocity that was scary above 70 just by going to a P5X prop. Boat runs 85 now and my wife can drive it too.

Rookie

iTrader: (4)

If you've done it before then you know the work it takes. I'd try to get a video of the boat running in calm water and see where the water breaks at.