Oh oh!

[Squirtcha?]

Well ran the boat up to the lake tonight. A couple buddies are boat sitting it until I can get back up there tomorrow night to begin my holiday weekend.
It's the first time I've had it out since repairing and straightening the bottom. I have a really really nasty porpoise for the first time in the boat's life.
Once on plane it's happening at all speeds (although it gets worse as speeds increase). I can't adjust it out with the diverter either.
I knew I should've taken it out prior to the holiday weekend. Looks like I've got some tuning to do now. Didn't really wanna have to mess with it while my girlfriend and the kids are all there. It's so bad I'd almost call it undriveable right now, so I reckon I don't have much choice.
I know I can take some of the wedge out of it and drop the plate some (currently 4.5 degrees of up wedge and 4.5 up on the plate). Hopefully getting some of that up angle out of it will be enough to settle it down. I'll also take some shoe shims along to try as long as I'm at it.
Any tuning ideas would be appreciated.
No racing for me this weekend, unless I can figure this thing out.

[stashtrey]

Stick a few cases of Budweiser up front.... that should help weight it down. :D

[Squirtcha?]

Not a bad idea except for the fact the porpoise problem would mysteriously (and progressively) return after a few hours.

[stashtrey]

Okay.... scratch the 3 cases and come by my pad... I have a keg in the garage. That should work!

[squirt]

Dan, After the bottom was done on mine I picked up one hell of a porpoise. I've played around with the plate, shoe, loader, wedge and pretty much have it under arrest but it's still there lurking. The lighter my boat gets the more it appears. With passengers it almost never happens. Sometimes I just have to back out of it and try again, other times I'm able to drop the hammer and blow right past it. It's always worse in smooth water, and can porpoise to the point of scuking air in the pump. Don't let it ruin your boating weekend with the family, have fun at the lake!
Don

[GunninGopher]

If you can't tune it out I have a suggestion. I sometimes will give the wheel a slow wiggle, to set the boat on a side a little. That seems to get the porpoise out of it for a little while. I seldomly give it full throttle, so I don't know how that would work going over 40 or so.
Otherwise I have to back off it for a sec and then get back on it. I've never had a really fast jet, or a dirverter, so that's about all I have to correct it.

[UBFJ #454]

Dan -
If I remember correctly, the hook you took out was one that would have caused a fair amount of lift in the back of your boat forcing the nose down ... having taken it out, it, the lift, may not be there now and, your right, 4.5 up may be too much up wedge now ... the bow now may be riding too high and you may not haxe enough range in your diverter to force it over enough.
Like you said, try taking some wedge out of it (I'd start by taking 2 degrees out) and see if it gets better ... if it does keep taking wedge out in 1/2 degree increments until you get the nozzle diverter into its proper range ... remember its principally about nozzle & ride plate angles to start with ... shoe depth may come into play for fine tuning once you start to settle the boat down.
You and Yours have a Good & Safe Holiday up at the Lake.
Jak

[Squirtcha?]

You did the bottom on that boat a year ago, I think? Funny how every boat acts different to various hardware and adjustments, even if the boats are identical. Just shows you had it working perfect once and then you touched it/repaired it and things changed... Am I right you had it working well I thought?
I blueprinted the middle section last year (from the center out two strakes). This year I had some delamination in the area outboard from there, so I did that over the winter. Repaired and strenghtened the bottom and straightened/blueprinted it. I think what this is telling me is that the hook in that area was still greatly affecting the handling of the boat. Even though most would say that the outboard area isn't important because it's not in the water while at top speed apparently mine was.
Like you said, try taking some wedge out of it (I'd start by taking 2 degrees out) and see if it gets better ... if it does keep taking wedge out in 1/2 degree increments until you get the nozzle diverter into its proper range ... remember its principally about nozzle & ride plate angles to start with ... shoe depth may come into play for fine tuning once you start to settle the boat down.
You and Yours have a Good & Safe Holiday up at the Lake.
Jak
Thanks for the input Jak. I've got lots of wedges and hope to be able to hit a combination that works.
I didn't figure the shoe to help out the problem, but as long as I'm crawling around under the boat................I might as well try it again. I haven't tried giving it more shoe since I did the bottom work. It didn't like/need it before and that could likely be the case again, but what the heck. I'll give it a go.

[LakesOnly]

Dan,
My boat took a nice set at 70 mph or so when I first acquired it. After my motor rebuild and getting the boat to 85 gps, the porposing was very prominent (does this sound familar?). Trimming it out with my diverter (by dropping the bow) reduced the porposing but slowed the boat down big time (sound familiar? :D )
I believe that you and I have essentially identical hulls bottoms on our boats, and both boats have about the same top speed.
Well, I called MPD about 10 days ago, to price the cost of a shoe and ride-plate for my boat...cost of the hardware and/or cost of hardware + install (I just ain't got the time). We spoke for a bit and Jack said that he is well aware of the way these hulls behave above the speeds we are at and that--in my case--a shoe & rideplate isn't necessarily going to eliminiate my (and perhaps your) porposing problem. He said that in a very similar boat, adding the shoe and rideplate got the boat to about 92 mph (as I recall), but with the increased speed came ever more WILD porposing.
So they added trim tabs to the transom. This smoothed the ride, boat took a good set and now hit (as I recall) 96 mph...dead flat set.
The other nice advantage to the trim tabs is that our hull design incorporates a rather deep V (compared to, say, a Sanger Jet) and the addition of trim tabs hold the hull firmly in the water. This prevents the boat from riding too high, which in turn helps reduce the chance of chine-walking...something I'm sure you and I are both aware of as we are on the brink of this based on the speeds we are pushing our particular hulls.
Call Jack and discuss this with him; hope this helps.
LO

[olbiezer]

dan if u remember i had the same problem with the old biesemeyer at all speeds......dropped the plate 4 turns on the turnbuckles and dam if it didnt stop porposing......then i sold it lol wish i had it back now lol

[78Southwind]

Dan,
My boat took a nice set at 70 mph or so when I first acquired it. After my motor rebuild and getting the boat to 85 gps, the porposing was very prominent (does this sound familar?). Trimming it out with my diverter (by dropping the bow) reduced the porposing but slowed the boat down big time (sound familiar? :D )
I believe that you and I have essentially identical hulls bottoms on our boats, and both boats have about the same top speed.
Well, I called MPD about 10 days ago, to price the cost of a shoe and ride-plate for my boat...cost of the hardware and/or cost of hardware + install (I just ain't got the time). We spoke for a bit and Jack said that he is well aware of the way these hulls behave above the speeds we are at and that--in my case--a shoe & rideplate isn't necessarily going to eliminiate my (and perhaps your) porposing problem. He said that in a very similar boat, adding the shoe and rideplate got the boat to about 92 mph (as I recall), but with the increased speed came ever more WILD porposing.
So they added trim tabs to the transom. This smoothed the ride, boat took a good set and now hit (as I recall) 96 mph...dead flat set.
The other nice advantage to the trim tabs is that our hull design incorporates a rather deep V (compared to, say, a Sanger Jet) and the addition of trim tabs hold the hull firmly in the water. This prevents the boat from riding too high, which in turn helps reduce the chance of chine-walking...something I'm sure you and I are both aware of as we are on the brink of this based on the speeds we are pushing our particular hulls.
Call Jack and discuss this with him; hope this helps.
LO
Paul
Sounds like your talking about this boat.
http://www.***boat.com/image_center/data/520/1676BN_Southwind_Rear-med.jpg

[tahitijet]

Dan,
My boat took a nice set at 70 mph or so when I first acquired it. After my motor rebuild and getting the boat to 85 gps, the porposing was very prominent (does this sound familar?). Trimming it out with my diverter (by dropping the bow) reduced the porposing but slowed the boat down big time (sound familiar? :D )
I believe that you and I have essentially identical hulls bottoms on our boats, and both boats have about the same top speed.
Well, I called MPD about 10 days ago, to price the cost of a shoe and ride-plate for my boat...cost of the hardware and/or cost of hardware + install (I just ain't got the time). We spoke for a bit and Jack said that he is well aware of the way these hulls behave above the speeds we are at and that--in my case--a shoe & rideplate isn't necessarily going to eliminiate my (and perhaps your) porposing problem. He said that in a very similar boat, adding the shoe and rideplate got the boat to about 92 mph (as I recall), but with the increased speed came ever more WILD porposing.
So they added trim tabs to the transom. This smoothed the ride, boat took a good set and now hit (as I recall) 96 mph...dead flat set.
The other nice advantage to the trim tabs is that our hull design incorporates a rather deep V (compared to, say, a Sanger Jet) and the addition of trim tabs hold the hull firmly in the water. This prevents the boat from riding too high, which in turn helps reduce the chance of chine-walking...something I'm sure you and I are both aware of as we are on the brink of this based on the speeds we are pushing our particular hulls.
Call Jack and discuss this with him; hope this helps.
LO
I've had the same conversation about my boat wtih jack.. and also with the owner of the boat jerry posted above. The owner posts on here or use to under i believe the name BN... Very nice guy with lots of info.. If i rember correctly he had a ride plate,shoe,loader , and a diverter, no droop. He said they tried everything and the instant the put the trim tabs on the problem was solved.

[Ken F]

Dan,
If you decide you want to try trim-tabs, let me know. I've got a set from the old Omega I'll send you.
ken F

[Danhercules]

"The Man" aka , Futs' Dad, who built the Southwinds, warned me about doing the bottom of my boat. I now know why. I would take Pauls (Lakesonly) advice.

[Squirtcha?]

Thanks for all the replies guys.
I ended up taking 2 degrees of wedge out. That put me at 2.5 degrees up wedge. I also took out 2 degrees of rideplate up angle which ended up around 3 degrees up. I think these settings are more typical for a semi-V with a straight bottom. Apparently my old setup (4.5 up wedge and 4.5 up plate) was just compensating for the messed up bottom. I always kinda suspected that and this whole deal would seem to prove it out.
It settled down very nicely with the new settings, and I could run it WOT off the bottle without any porpoise. I didn't gps it but I think I may have picked up a little speed too.
It was so rough yesterday, I didn't squeeze it until last night. Still pretty rough even that night and I had some trouble staying hooked up. Might be able to put some shim into the shoe now.
Also noticed that along with the increased speed from the juice, a little of the porpoise came back too. Probably take out another degree of up on the plate. Possibly take some more wedge out too, but I'll try just the plate first.
Anxious to take a test and tune day at the lake. After that I can pretty much rest assured that I'm optimized and can just go thump on it.
It's always difficult to tell by the seat of the pants, but I think it might be a little faster than it was last year once I get it dialed in.

[Ken F]

Good deal Dan! Glad that you got it worked out.
You know, you have sure learned a lot since we started on here. I know I have.
Ken F

[Nucking futs]

I had a real bad porpose problem in my southwind 20 and HAD to put tabs on it. After all the work I did this year ( reset intake new shoe and new engine) I took it out last weekend and noticed right away what a differance all that made. The lake was to rough to actually tell if the porpose went away but I went out yesterday and really put my foot in it and its all gone. My tabs are not even plumbed right now and at about 70 it started to hop just a tad but the diverter took it right out. It never made a diffeance before. I plan on still running the tabs for real rough water but im so stoked that i finally figured out the hop. The intake was set @ 6* and loading like a mo fo. I will take out about 2* of wedge and that should get me in the ball park.
Glad you got yours figured out Dan. I too picked up "ALOT" of speed.

[Duane HTP]

Put your ride plate down 2 or 3 degrees. Your boat doesn't have anything to ride on with it up that high.

[Squirtcha?]

Remember this setup Duane?
http://jetboat.homestead.com/5.5_degrees_cr.jpg
This was when I first made the switch from PD droop to the Snoot. All this angle (5.5 degrees) was needed to overcome the messed up bottom. Any less angle slowed it way down........any more made it porpoise like mad.
After doing the blueprint on the center section I was able to take one degree out of the wedge and plate (then at 4.5 degrees on both).
Now after doing the rest of it, 2 more degrees. That puts me at 2.5 degrees up on the wedge and approximately 3 degrees on the plate. Since it still porpoises when on the nitrous, I think I need to drop it down so it ends up at 2 degrees like you said. Hopefully that will settle it down.
Thanks for the offer on the trim tabs Ken. Hopefully it won't come to that. Very cool of you to offer it.
Dan

[Duane HTP]

Well, there's no definite answer. Each one is different. But, it sure sounds like less wedge and less plate angle is in order to try. It will take some playing around with the angles just like it did when you first put the Snoot on. What shoe are you running? Flat, Back cut, or Tapered?

[Squirtcha?]

Well, there's no definite answer. Each one is different. But, it sure sounds like less wedge and less plate angle is in order to try. It will take some playing around with the angles just like it did when you first put the Snoot on. What shoe are you running? Flat, Back cut, or Tapered?
It's a backcut with the leading edge approximately 1/8" up in the hole. Before doing any of the repairs/blueprinting, shimming it down made it way violent on shutdown and didn't do anything for top end (or anything else for that matter).
I didn't notice any difference when I made the change from a flat shoe to the backcut, but I made the change prior to doing any of the bottom work and the wavy bottom was probably counteracting everything else anyway. Seems to me that with a hook, the bottom and the backcut shoe would be fighting one another? Just a theory on my part.

[Duane HTP]

Before doing any of the repairs/blueprinting, shimming it down made it way violent on shutdown and didn't do anything for top end (or anything else for that matter).
That's exactly the point. What you did before, don't matter now. Start over. You have a different boat now.

[PC Rat]

What actually causes a boat to porpoise?

[396_WAYS_TO_SPIT]

Dan, Im glad you getting her worked out. I asked tom papp what the plate angle is supposed to be and he told me it should be about 2* up from the shoe. If your running more then you are fighting hardware. He said the intake charge is too high. I sure and the hell hope mine dont act like that:eek:

[Sanger Jet]

turn over one of the wedges so there zero then drop your plate a little till it's happy but not to wet........Thats what worked for me