Hey everyone, new to the forum and figured this is the place to ask after trying various things to get rid of a porpoising problem. Boat is a 1978 Tahiti super tiger with hook removed and pump set back at -4* . Berkeley pump, split bowl, inducer, A-impeller, manual diverter, modern style place diverter nozzle. Has a ride plate and back cut shoe. Blown 427 on mild boost. Seems to be spinning about 5400rpm at almost full throttle before having to let out, but havent gotten a true good run for accurate numbers. Boat ran 88mph at its fastest once in rough water but is consistently limited around 70-75 max due to a porpoise that starts around 50 ish and just gets worse the more you lay into it, to the point of eventually hopping so bad it will lift the rear end out and cavitate. I have tried the following with no obvious  changes for better or worse in the ride and it still wont take a good set:
~Stock rock grate (with and without ride plate and shoe).
~Loader (with ride plate and shoe).
~Ride plate adjusted from slightly negative all the way up to about +5* and at various angles between.
~Droop +7* pin angle
~HTP Straight snoot 0* pin angle
~Wedges on both snoots adjusted from -1* up to +5* of wedge.

I understand this is not a race hull and not designed for speed but I want to make the most of it. The boat started off with the intention of being a cheap project boat to just go screw around with on the lake when I was 17 and I ended up doing more with the paint job than originally planned and have too much time invested into this hull already at this point so I figure something can be done even if more significant modification or hull work is needed to help get rid of the porpoising. My thoughts from here and plans of next things to try are:

~Extend the strakes that die off just before the pump intake and bring them back to the transom. (Not sure if this would give it an inconsistent ride surface by coming on/off of the strakes at all then creating inconsistent lift)

~Life the boat and hang it. Take a straight edge to the bottom and see if there is any rocker or level issues in the hull that Im unaware of when unsupported by the trailer and with engine weight in it.

~Figure out the weight distribution of the motor in that hull and see how the current balance point or COG compares to an ideal percentage forward from the transom. It is a heavier thicker hull compared to some of the lighter faster hulls but looks similar in shape and profile. Not sure if engine placement would/could differ that drastically from other hulls or if it would be having such an effect on balance and ride. I wouldnt say its abnormally far back or out of place by any means but Im thinking it could potentially come forward and may be something to try.

Im open to any suggestions, ideas, or questions from anyone thats had this issue or has any experience with different hull patterns, measurements, or mods that could be of benefit. Ive messed with pump/ride plate angles, and thrust height quite a bit like I said with no real significant changes for better or worse so at this point Im kind of narrowing my mind around it being a balance problem or hull shape/design. Curious to hear any thoughts. Thanks! The pics of it running are at about 60mph and show the high and low side of the hop because it wont let me upload a video. It does even get drier than that sometimes. This behavior has been consistent with starting around 45-50 regardless of adjustments.

The loader mounting point looks like a brick bolted to the intake housing. Could be an optical illusion? The transition from the hull to the intake housing looks to be uphill, or downhill being right side up?
The texture of the hull forward of the intake housing seems quite course?
Not an expert by any means, just something I noticed in your pics.
I have set my own intake housing before, and the transition doesn't look ideal.
But mines an SBC and 55 mph, and not a hot rod, either.
Trim-a-step on mine were ~2/3? down and had a terrible hop.
Even with the hull solved that problem.
Impressed with the hardware that has been tried.
Rather than lifting it and straight edging it, measure it in the lake, divers mask and all...real world conditions.
Best of luck, post changes and performance.

Dan'l

I did end up playing with some more testing including swapping the loader for a stock rock grate again for a baseline and went straight snoot, droop, adjusted snoot wedging, moved the ride plate up and down, etc. Nothing seemed to really have any significant effect. I finally had a longer slip yolk driveline made using some of the parts from my current 1310 driveline that was an overall length of 8.25in, basically just replacing the factory H-joint with a 4in slip section that gives 2in of travel. The new one has ability to adjust from about 14-16in overall. This will allow for some weight balance testing by moving the motor forward to changing the center of gravity and compensate for the pump being set back then land it wherever it performs best. The porpoise seems to have been caused or at least worsened by setting the pump back which was moved just enough to get the inspection cap outside the transom (about 6in out from original position). I started by moving the motor forward 5.75in which is what this driveline would push it to at full collapse. It helped big time. Still feels like its on the verge of porpoising at certain points but it took a way better set and rode at speed much more like what I have been aiming for. High in the water and flatter without being bow high. Seemed to like the diverter in its most neutral position which with my setup is 1* up from keel, anything higher was seeming to create too much bow lift and provoke some porpoising again. Ride plate was set for that run at 3* up from keel. It also felt like it wanted to chine walk a little more than it did in the past but thats somewhat to be expected flying it lighter and actually getting it to hold position like that. Will need a bit more testing and didnt have an opportunity to get as many hits as I wouldve liked, too many people on the lake limited brief windows of decent water, but I will be moving the motor forward another 2in because like I said it still almost feels a little bouncy or on the verge of porpoising at a certain speed range and kind of drove through it but curious to see if a bit more movement does much. I think its very close to where it needs to be and could be about on the teeter totter point of ending up further forward than necessary but only more testing will decide that and where its happy spot is. Havent found much info on anyone discussing similar issues and even less that have actually documented consistent solutions other than putting cav plates or tabs on which seems to just be a bit of a bandaid and that wasnt something I was interested in doing if I didnt absolutely have to.  I have made some temporary extended rails off the quarter stringers and cross braced the rails to the floor. They are pretty freakin solid for a temporary testing setup and working well so far but again temporary and will
Probably have a few sets of holes until the best location is decided. My plan is to go full stringer in the future, have a beefier solid 1350 driveline made that wont slip and build new permanent rails once we find the right spot to land her. A dolly trailer will also be in the works at some point! I added some pics of the driveline and location of the motor now as mounted for visual.