Drives not working evenly
 

We recently bought this '98 353, and I noticed an evolving problem of the drives not moving up/down equally. The port drive would move more briskly than the starboard, and the starboard pump motor just sounded anemic by comparison. After visually inspecting the pumps and cylinders and doing lots of searching, I had decided it was most likely a weakening pump motor. So I figured I would order a motor and swap it in and see if that had an impact. But before I could get it ordered, we were at the lake and after accidentally selecting the port batery switch for starting, the engine wouldn't crank. Dead battery. Then it dawned on me that the failing battery might possibly also be the trim culprit. It was. I replaced the battery and the drives work 1:1 as they should. I'm posting this for future reference given I didn't find anything like this when I searched.

Jim

As near as I can tell, OilDyne (pump manufacturer) has never built two identical pumps. In all fairness, there are a number of high-pressure and return valve adjustments that can be made, but it's tricky, and you can screw things up pretty quickly if you're not familiar with them.