Re: Steering (cable pully)
Those cable and pulley systems were used for years on motors 50HP and less. It is a good idea to make sure the mounting hardware is secure to the hull. One spring only is advised to keep the motor from a possibility of fishtailing.
True on engine size. Back then 35 hp was about tops till the OMC "Fat 50" arrived. Don't know what that they used with that. I certainly wouldn't hook up a hot mill of today to it, but with a 15' boat you aren't going to be going over 50, or not much, maybe a 70 triple and I wouldn't have a problem with that.....unless it proved to me to think otherwise.
We ran wires down both sides if you had a front deck, hence forward mounted helm with springs on both sides, or if a side mounted console wires went down the side with the helm with one cable crossing the transom under the engine, being secured with a pulley and returned to the engine for another pulley and back to the same side for termination. We always used, and I always saw 2 springs used.
Fishtailing (vibration of the engine back and forth) could be a possibility but apparently we had enough tension on the engine/engine bracket tensioner, and adequate tension on the springs. Never saw nor heard of it........but if it didn't happen why would you (Chris) mention it!
Mark