my boss just bought a '78 vector

[brian1570]

So what exactly causes porpoising in these boats? Conventional knowledge really doesn't seem to apply to these hulls.

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[transomstand]

So what exactly causes porpoising in these boats? Conventional knowledge really doesn't seem to apply to these hulls.

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A VERY complex question, but it all comes down to angle of attack. As the hull "pushes" through the water, a wave builds in front of it, as the boat "climbs" it, the hull rises, as it "falls off" the other side, the hull drops.

[brian1570]

Haha ok I know that much. I guess should have asked how does one go about solving the problem?

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[transomstand]

Haha ok I know that much. I guess should have asked how does one go about solving the problem?

[ Post made via iPhone ]

That's the $64,000 question. This is where experience plays such a big part, you need to feel what the thing wants, not so easy when you don't know what your feeling.

Most likely, it will not be a single change, and be extremely sceptical of "all purpose" answers like "just raise the motor", or "move the battery", etc.

The first order of business, is to decide exactly what we want this boat to do for us. Do we want a fun boat to bang around on weekends, with a top speed of 65 or 70, or do we want the most killer fast thing on the water?

Either way, we need to start from scratch, and examine the hull, engine and setup from the beginning, to insure we have what we need to make it all work. Wish I had a better, easier, and less costly answer, but that's the "fun" of performance boating.

[brian1570]

65-70 mph with no porpoising is the goal. We just installed the jack plate this morning. Which has 5.5" of set back and we are going to start level with the pad and go from there. Prop is still a 24p chopper. I think he also has a set of solid motor mounts waiting to go on as well.

Oh and I meant to mention the whale tale. Not sure if it's hurting us or helping.

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[Surface Scratcher]

Just like chine walking, porpoising is a cycle. It starts and if not corrected, it gets worse. Once you make a correction, it can change the cycle and things start to level out. What I'm trying to say is, as you get to know the boat, you will anticipate a cycle. Make your correction early, whether it is a trim adjustment, acceleration, etc., and then check to see if it is getting better. If so, don't make more adjustments, let the cycle finish.

Of course, moving weight forward may help but is a speed killer. Motor height and prop selection could also help. This is all part of fun of getting it set up.

[transomstand]

65-70 mph with no porpoising is the goal. We just installed the jack plate this morning. Which has 5.5" of set back and we are going to start level with the pad and go from there. Prop is still a 24p chopper. I think he also has a set of solid motor mounts waiting to go on as well.

Oh and I meant to mention the whale tale. Not sure if it's hurting us or helping.

[ Post made via iPhone ]

Try it with the plate and see how it changes it.