Aggressive Yaw/Roll on Ocean 66SS with following seas

Where are your fuel tanks located? Why would you only carrying 20% fuel? Is this the same boat that has a bad starboard fuel tank and you're only using the port fuel tank? A jersey style and Ocean hull will be squirelly in following seas to start with (look at the beam of the hull at the front of the house and how narrow the beam is at the stern). Having a dinghy on the bow and waverunner is definately adding to that, as does the weight of an enclosed bridge up top, and having very little fuel (weight down low) is only going to make matters much worse. My recommendation would be to keep the boat full of fuel and when it get's down to 1/2 tank top it off again. It will also help keep condensation (moisture) out of your fuel. It will help on the ride. Also move any weight that you can to the stern of the boat.

In addition, I'd carry full water tanks as well, you have a top heavy boat, that notoriously is not a good down sea boat, and have done your best to exasperate the problem. Also when you're out for the day get rid of the fore deck weight...leave the toys on the dock.

I used to run a 43 up and down to Florida. Notoriously bad in a quartering sea. It's a trade-off. That narrow transom helps you get more speed on a flat sea and better economy.
Two stories I often tell about oceans:
One was coming into Ocean City, Md. having to go from full throttle forward to full reverse, and using the wheel, gears and trim tabs to keep it straight.
The other was when we followed another 43 out of Hilton Head in about 12' seas. He was on autopilot. First I'd be looking at his transom; next the front of his bow rail, and so on. His mate was hanging off the stern chumming. If I didn't tell him to get off autopilot he'd have probably rolled it.

Yep that's an Ocean. But the tade-off is for speed and good fuel numbers. We ran at 29 kts., and burned something like 21 gph with Yanmars.

P.S. We started every day with full tanks. It's just the way they run.

You left Hilton Head in 12' seas in a 43' Ocean instead of taking the ICW??? Are you nuts? LOLOLOL

We were running for St. Augustine. Inside we'd have only made Fernandina. That's transporting with a boss on board who says 'Go for it'. LOL. We did Fire Island to Miami in 5 days, stopping every night. Second fastest boat I've run down the coast.

Welcome to Ocean Yachts, do as suggested above, but that is the nature of the beast. I remember running back in a 48' viking with a similar Ocean Yacht in 4-6' following sea, I was sitting in my chair steering gently with my feet and the other Capt. was working his a** off trying to keep the Ocean strait, and he was failing miserably!

Does anyone have any experience with the trim tabs hat have turned down edges? Will this help with a following sea? Maybe help prevent surfing? Probably not enough surface area to make a difference. Probably get bent or ripped off?

Do you mean the blade type that just extends straight down a few inches below the hull made by Quick, I believe. Cabo started using them and they were very effective at trimming the boat. I don't know how they would be in a following sea. Basically the issue with Oceans and the narrow transom is the foward area of the hull has a lot more drag than the stern, so the bow slows down yet the stern doesn't have as much drag and it tries to keep moving foward and ends up spinning one way or the other.

DK about getting ripped off or bent, but I doubt they'd have a big effect in a following sea on an Ocean, except for a little when you're using them to help steer with. That's really not what they're designed to do.
P.S. one thing I'll add about that 43 is that I once took the run from Fire Island to Atlantic City and found myself in probably 18' seas (only way to see sky was to poke my head out from the bridge and look up. I was working so hard I couldn't let go of the wheel long enough to put a PFD on, which is when I began wearing it every time I break out an inlet. However, we made it. So the boat and I did our jobs. It's also when I learned about Dial-A-Buoy, because the forecast was for 4'-6' but neglected to mention they were atop a 10'-12'swell.

I believe they were designed to make the tab more efficient in lifting the stern, thought maybe it might help keep the stern from "spinning one way or the other". Kind of like a keel except not.

would big oversized rudders help?

I agree with the posts in this thread, You have to keep the weight off the bow, zero tabs, and weight in the stern (fuel, water, whatever)

Would increasing rudder size help in any way? Intuitively I would have thought that a narrower transom presented a smaller surface to a following sea? Snowed in again in NY....

SMR

This is a traditional SF with an enclosed bridge, but no aft cabin, etc? What kind of sea state are you running in? Just hard to understand (for me at least), that even with improper weight distribution, how a 66 footer gets pushed around in recreational seas? BTW, what happened to the OP?

Yes, large rudders would help.

Actually I doubt larger rudders would have much effect. Remember, rudders need water moving past them to have effect. In serious following or quartering seas you're surfing more than running. It's the water catching up with you that causes the yaw. It's like being in reverse.

They still have water running over them, also the larger rudders create more resistance or drag to side movement. Is it a cure all, no. But it will help.

I think the key is to accept the boat's personality. If you want a battle wagon get a Viking or such. If you want a boat that'll get you to the fishing grounds fast, ecconomically and backs down good get an Ocean.