Prop question on a 20'

[Bushwacker]

Originally Posted by Sceptre20

I have a 20' Sceptre that is powered by a Yamaha f100 four stroke.I am running a four blade prop on it and find that the boat is unresponsive at slow speeds,it requires constant adjustments at the helm to stay on course and when docking or loading onto the trailer it is very slow to respond,the steering is a brand new baystar hydraulic unit and seems very tight.I was wondering if the four bladed prop could have anything to do with the problem and if others had experienced the same problem.any input would be helpful.

Sounds like you're simply talking about a slow steering ratio. The prop has nothing to do with that, and Gillie's right, if anything a 4B prop will improve response.

I'm not familiar with Baystar, but I think it's just a cheaper version of the Seastar system, which has 3 different size (displacement) helm pumps. If you have the small size pump, it'll take about 5 1/2 turns of the wheel to move a Seastar hydraulic cylinder lock to lock, and that's pretty slow, especially if you were used to a push-pull cable system, which is typically around 3-3.5 turns. I went with the medium size helm pump, and mine is about 4.5 turns for full stroke of the cylinder, which is still pretty slow but it turns real easy. I'd suggest you disconnect hydraulic cylinder from tiller bar on motor and try turning motor by hand to make sure the bearings in steering shaft aren't dry or binding. Also check the hydraulic lines to make sure a line isn't pinched somewhere, because that would restrict flow and make the helm hard to turn. Those hydraulic helms normally are very easy to turn.

Low speed wander and slow steering response is normal behavior for all planing hulls at low speed, although the "multiple keels" of the VDH makes a SeaCraft track better than most; it just takes some getting used to. You may be over correcting due to the slow response; if you just turn the wheel a small amount and then wait for it to respond, you may find it easier to hold a steady course. Trimming the motor down will also improve steering response.