Hello,
I'm new to the Active Thunder camp. I've had a few other offshore boats in the past: Scarab 29, two Donzi 28 ZX's but I wanted a great running offshore hull with a single engine for simplicity. The Tantrum I purchased is a 2000 Model with an HP500 and Bravo XR drive. It has steering dampeners on it but not hydraulic steering.

The boat seems to handle the rough water here in Atlantic Canada very well however as the boat approaches 70 mph on the GPS it begins to oscillate (chine walk) and it eventually gets so bad I can't control the boat and I need to slow down and gather it back up. I've tried running with the tabs at neutral (cuts a lot of speed) and I'm not trimming the drive past neutral at any time. I've tried two props a Bravo 1 26P and a Bravo 1 28P. I would assume I should be able to trim past neutral for a little more speed with this hull. I'm wondering do I need to upgrade to hydraulic steering to be able to steer through the chine walking on the boat or is there something else I should be looking for? I can't seem to find any threads that pertain to this so I'm wondering if there's something I'm missing. I appreciate any help you may be able to give me.

1) Disconnect the stabilizers, and wiggle the drive back and forth. How much does it move? Stabilizers often hide gimble wear issues.
2) You need hydraulic steering. IMHO anything with a "blue" motor's power needs hydraulic steering, ESPECIALLY in this size boat. That is usually conventional thinking as well.

Thank you for your thoughts,
I disconnected the stabilizer bars and there is about 1-1 1/4 inches of play total (1/2-5/8 each way) at the back of the drive. Will that be enough in these boats to cause a bad chine walk? I also noticed the the drive isn't aligned perfectly in the center of the point of the V. Do they offset this slightly to compensate for torque or should that also be aligned?

That kind of play is definitely your primary issue. Your gimbal ring and steering pin likely need replaced. And while you are at it, go ahead and install at least a single ram hydraulic steering system as your winter upgrade project. I'd suggest Imco.

our tantrum has no steps and runs very hard with total control ,we can overtrim to throw a rooster tail with no ill handling we do run the 380 tabs a 26 p bravo prop and an XR

Thank you for your reply, Do you have hydraulic steering on your boat?

you need to check the side to side play with engine running, probably be less

If you lift up on your drive is there movement then? I have the IMCO hydraulic system and it works great. No left to right unwanted movement at all. They sell a 1/2 kit that connects to your Brazilian(?) valve and then out to your new hydraulic ram(s) and you keep the cable from the helm to that valve but if you have a lot of movement in the steering wheel while driving that kit probably won't fix that. You'd have to go full hydraulic for that.

If you have that much movement, you need a new or rebuilt Gimbal Ring and steering pin aka swivel shaft https://jrmarine.com/
Hydraulic steering won't fix your problem, but it will help prevent it from happening again.

Okay, I’ll check the gimble ring for damage and change the pin.

Will a single hydraulic ram kit do the job well with this boat or do I need to spend the extra for the dual ram kit?

Once the gimble is tight and the hydraulic steering is installed would you expect the chine walk will be remedied?

I bought the Tantrum based on owners belief in this hull and it’s capabilities compared to other offshore single engine boats this size. I don’t mind making the investments to make it run properly if it’s going to run really well when I’m done.