boat getting "loose" at speed...

[Sandahl]

I moved recently and now that I'm boating on a smooth lake with room to run fast and straight instead of a rough ocean, I've run into a new boat handling phenomenon.

The boat is a heavy old 1970's Cigarette 36, weighing 11,000+ and it has a 9-1/2' beam, Hydromotive Q-IV's turning inward on TRS drives, and a pair of 600 hp BBC's. It's got a single sidewinder stabilizer at the moment but otherwise standard power steering.

Around 65mph on gps the boat starts to feel likes it is very light and it could walk side-to-side at any instant. It will pull past this speed by a few mph but I always end up backing off to get it feeling solid again. Trim is usually ~2 out from straight on the indicators (4 out from fully tucked under).

Is it possible to drive through this and learn the handling?

Or does every given hull and setup/weight have a speed where it gets loose - with this being such an old, heavy and wide boat maybe I've reach what is my top safe speed?

Other comments?

[jpclear]

I just can't imagine that much boat getting that "loose" at 65 mph. Seems to me that you MUST have steering or hull issues. --- Jer

[Dave M]

I just can't imagine that much boat getting that "loose" at 65 mph. Seems to me that you MUST have steering or hull issues. --- Jer

I agree. Is your steering as old as the boat? Get a better quality steering system. I don't think those sidewinder stabilizers are adequate for big heavy boat.

[Sandahl]

Steering - good place to start. I didn't really know if it wasn't just normal. First I'll get the other sidewinder back on and see if that helps, otherwise look at external steering. Thanks for your replies!