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.
