What the difference between a hydraulic helm for an IO vs an OB? Found a used SeaStar SKU:HH5779-3 / UPC:HH57793. It's listed as OB some places and universal others. I want to add external steering to an IO. Any help is greatly appreciated.

Typically an I/O is going to have a power steering pump mounted to the engine whereas an OB will not. The OB helm acts as the pump whereas the I/O does not.

This may help.

you need to match the volume/flow of the helm with the cylinders and there are a lot of variables... you could get it right or end up with too many turns lock to lock and insensitive vague steering or not enough and twitchy steering.

That's what I was thinking. I can get everything needed thru our shop customers except a helm. I'll have to check volume of the cylinders and go from there.
Thanks Guys

I have a hydraulic helm on my 30' Cobalt with power steering pump. My Arnesons had no provisions for cable. For high speed testing I had the rams in parallel, slowing the steering remarkably. I never did bother going back to series plumbing because the extra few turns didn't really bother me. Never missed the steering on the I/O TR's.