Added weight and started porpoising

I added two #350 fat sacks in the engine storage areas and #300 lead to the front of my 98 centurion elite v-drive this weekend. The boat has no stock ballast so this was the total weight plus about about #800 worth of people. It sure improved the wake but at anything over 30 MPH it started porpoising. As I added speed it got realy bad.

Has anyone had this experience? What did you do to correct it? One person suggested I lower my cavitation plate?

I believe if you add more weight to the front you can correct this problem. If you are driving 30+, maybe just empty the back sacks and leave the lead up front.

Yeah, my Super Air Nautique will do the same thing if I fill the rear tanks. I added a couple hundred pounds of lead in the very bow and it helped a lot

rod

Maybe a stupid question, but what the heck are you doing driving 30 mph with ballast and a crew? You're like 500 pounds over the certified weight and driving at slalom speeds - at least, you should expect some wierd handling issues; at worst, you're looking for trouble (chine lock, etc).

Then again, my boat porpoises without ballast when over 30, and feels chine lockie about 35, so I got no room to talk.

I think you might be on to something Derek. Loading up your boat's ass end and driving fast sounds like a bit of trouble to me.

Derek

First time out with the ballest. I filled at the houseboat and drove 10 min up to good water. Next time I'm going to the good water and then spend the time to fill. Whats chine lock?

Brad

My i/o has porpoised from the day I got it. Light boat, 350 engine, back bench seat. All the weight in the boat is behind the driver. I put a few hundred pounds of lead int eh frint and it settled down a lot. Most boats have a rear weight bias, so putting some up front will help handling charecteristcs.

My boat does the same thing... I just ask people to sit up front... then it drives nice!

I don't know the textbook definition of chine lock, or the dynamics behind it, but think it's basically the boat entering a turn it can't recover from. Steering effectiveness goes to zero. I get the impression that it's affected by one of the usual design challenges like stable vs. responsive or quick planing vs. smooth ride - each boat or car or plane will pick a different spot along the line. Of course any boat that comes from the factory with excessive chine lock is a lawsuit waiting to happen (Toyota recalled a whole stack of 21's because a mold had gotten warped - replaced all the potentially tweaked boats with brand new ones).

I feel it when I'm mid thirties and higher, but not when the water's smooth. Just feels a little squirrely, like the dead band around the rudder increases or something. Not a real comforting feeling, but I haven't driven a lot of boats at those speeds so have little to compare to. Do know there's usually no good reason to be driving that fast, but that twitchy feeling just nags a little.

Unless the water's really smooth, I don't think you should be heavy and driving over like 25, but that's just IMHO. Even if your riding area is ten miles from the houseboat, slowing from 35 to 25 would only cost you 7 minutes.

I had to keep it at 30 and that was fine. when I emptied the sacks and just had the lead in front it ran smooth all the way to full throttle.

I run my SANTE at full speed 45-50 MPH while all my tanks are full with five adults in the boat. I have never experienced bad handling except for the porpoising, which is solved with additional people up front, or dumping the rear tanks only.

I would say it has to do with the placement of weight in the boat more than the amount of weight in there.

You can also add a hydraulic wake-plate, and it will stop your porpoising entirely.

I assume that what I call my cavitation plate is the same as a wake plate. how much should I lower it below the level of the hull. I was going to start with about an 1/2 inch.

1/2 inch is probably more than you think. Try half that.