Porpoising questions...

I have a 68 mustang, dad bought it new. It's always porpoised above 3800 rpm. WOT was never an option unless there were 3 people in the front seat and nobody else on board. Since a recent rebuild with engine change (351) and prop change (12x14 cupped), the porpoising starts at the usual 3800, but then at WOT the hull seems to nose-down & 'stick' to the water. Steering becomes almost unresponsive until you back off on the throttle and push the wheel hard either left or right - the hull 'pops' loose and you're in control of the steering again. What gives???

Robert,
I tried to email you at veasybottom@aol.com and the address is 'undeliverable'. Is it spelled correctly?

I appreciate the offer - it's very kind and generous. I have some questions before I accept: I don't like the idea of making hull penetrations for the sake of experimentation, so I would like to know a little more.
- How and where were these wedges mounted?
- Were these designed for this purpose or are the 'homemade'?
- How did they impact your wake pattern?

My Mustang will porpoise at 25 or 30 mph if I have 2 or 3 passengers in the rear. It's frustrating because we often load up the family or friends for a cruise around the lake and I can't go fast, but of course everybody wants to! It's got a 351 in it now and it sure can move when you want it to, but there is a lot of top-end that I can't use. Hole-shots are great though.

Jamie,
I'll be in Nashua this weekend for a wedding. Where is your boat located in relation?

Ken, our boat is on Merrymeeting Lake in New Durham, NH.

Kenny, well, as to the water logged foam situation, I replaced the wet exhaust tubes and found very little in the way of saturated foam. There was a small amount of water evident, but only the very bottom half inch of foam. I did some checking under the seats and found no moisture under there to warrant such an odd handling situation. Thing is, why would the boat just do this on right hand turns? Odd...

Just throwing this out, no facts or science offered!

Is it possible that CC spent so much effort on the hull design of these early models to make them track well through a slalom course that they sacrificed (or lost) some steerage?

-OR- Is it possible that the repowering with the 351 is pushing so much water past the rudder that it seems 'frozen' until you back off? Are the rudders for a 302 and 351 boat the same size? The added hp may have something to do with the porpoise issue?

Like I said, no science here, just thoughts.

YellowDog: I'm pretty sure that part of my problem is because the boat is overpowered. I never thought that I would admit that ANY vehicle could be OVER-powered; never enough horsepower, you know. But this might be the case with my Mustang. The prop (12x14) is pushing a lot more water than before when it originally had a 12x12 prop. I was going to throw the 12x12 back on and experiment a little, but I'm afraid of over-reving.

KennyG: It sounds like Jamie and I are having the same 'hull sticking' issue. The boat will be porpoising and then suddenly 'stick' to the water. Bouncing of course stops and the boat goes like hell. But it does have a right-hand pull (I would never let go of the wheel at this point because of the intense pressure I feel on the rudder). As I back off the throttle, the boat pulls down even harder until the 'pop' occurs and the boat returns to a normal plain. It's not a comforting feeling at all when it's sticking.

I think I'll try Roberts wedges and see what happens.

Kenny G: The 'reids rides' discussion started someplace else...what did we miss?

What is "rake"? They mentioned it a few times when talking about their props.

None the less, what I'm getting out of all this is: by oversizing the powerplant and screwing with prop sizes, we are pushing these hulls beyond their design capability. These boats were not designed to go much over 40 mph and aren't supposed to be speed-boats. By trying to make them such, we are only looking for trouble.

With that said, I guess it's time to admit to myself that my little Mustang will never be the same as having one of Reggie Fountains 47' Lightnings.

Woe is me.

I'm jumpin in! Most all of what Ken is experiencing with his 68 Mustang I've been thru for 5+ years and still go thru with my 70 Mustang (Diaries, light blue 1970). I've come to sadly accept and agree with Ken that it's the result of pushing this hull faster than it was designed to go in its current bottom configuration. This hull has significant hook designed in it to keep the nose down and attempt to limit the porpoising. The term Ken used for the hull to "stick", I also know too well. I've seen this in two of our boats and yet never felt it in any other boats below +/- 50mph. You throttle up and hit a certain higher speed and the forward hull portion instantly, not gradually, sucks down to the water surface, and you immediately feel the extra drag. Decelerating in my 70 from higher speeds with a boat load can be uncomfortable also with a tendancy to pull and lean to starboard. My 73 Mustang, while stock and not nearly as fast, still on occasion will nicely and gently reach top speed only to have the nose instantly drop down slightly and actually lose a mph and 100 rpm and for several years I thought I had a slight high rpm engine problem until finally realizing what it was doing. With a bit or weight in the back seat it doesn't do it. And the 73 doesn't exhibit any of the unusual handling characteristics of the 70, but they are two different hull designs. Ken, if you'd give me a call sometime at 704-451-5080 I'd like to hear more about your boat and how it handles. Thanks.      

Kenny G: I gotta' party with you!
Old Correct Craft = chick magnet

regarding the wedges: I think you're right. THey will provide more hook and only intensify my high-speed hook problem. However, if I want the boat to cruise around the lake nicely at 35 mph with 2 or 3 people in the back seat, then I think I have to add more hook (via the wedges) to keep the boat from bouncing.

Do I have it right or do I have it backwards?

When I bought my boat last year it had some steering problems similar to those mentioned. I found and fixed all of the "play" in the steering linkages and the problem disappeared. Now my boat does ~50mph and handles PERFECTLY!

My 77 leaked at the bow eye during idle speeds. I removed the eye and reinstalled with plenty of 3m dealent. Hasne leaked since.

I'm thinking the bow eye also as it appears to be damp around the base of it when I look up in there wiht a flashlight. Odd thing though is like this weekend I idled around for maybe an hour or so total and never got any moisture at all in the boat.
I'll pull it this winter and recaulk it.
Thanks