SkiDoc

iTrader: (4)

I added a single assist to a single engine 25' vee, it added a margin of safety, but it was not easy to deal with for the same reason I'll mention later. My current twin 27 cat came with an assist system as well. As for the problem.....especially with twins, when you want to quickly initiate a turn, you meet with a lot of resistance.....you are mechanically havining to initiate movement of the stern drive.......once the stern drive starts to move it feels alright......you think well if its just with quick movements I can handle it for the cost and hassle difference. I could not, this made putting the boat on the trailer much more difficult and avoiding drift was very fatiquing. And I'm not an expert on cables, but I can tell you there is a lot of stress on the cable to initiate movent of the stern drive and the cable will wear much faster than the stock set up. I put a hydraulic helm on my twin and can tell you that it was the best thing I've done to the boat. My wife before I put it on was very nervous that she could handle the boat, now no sweat. Eric

Whiteknuckle

So are we saying that the extra strain on the cable is from steering wheel input to "energize" the valve direction and not from forces outside the boat? It appears to me that there should be some solution to this. I am not trying to be convinced, I just want to understand.

Falcon

Full hydraulic has the most capability for maximum steering loads. "External" cylinder assist is next and is much better than the stock cable "internal" cylinder assist.
As for the wheel effort at the dock, that has a lot to do with pump rpm at idle when compared to cylinder volume. The "brazil" valve also can cause some extra problems with this at idle, usually helped by increasing the pump rpm. That valve was sized for the needs of that small internal cylinder.

Scarab28

How do increase the pump speed, by putting a smaller pulley on it? Does this significantly help?

nauti-buoy

I think full hydraulic steering is the only way to go. I installed a full hydraulic dual cylinder system on my 28' single engine scarab last year. There is absolutely no play in the drive. I can now let go of the wheel while cruising and it roles right along in a straight line. Also i can now steer the boat with my pinky finger. It cost more but I think every performance boat should have hydraulic steering

Whiteknuckle

Nauti,
Yeah, I'm glad you like it and I'm sure that its great, but the question is why is it better and "safer" than the cable actuated system. I want to know why full hydraulic is safer. There are many people that just repeat what others say about everything without knowing the mechanical reason why. Thats what I'm asking for, and Falcon is trying. Break it down and make it simple to understand.

Falcon

Scarab
Look at your current pulley ratio. Some older stuff had pulley ratios of about 2:1, pump turning about half of engine speed. You want about 700-800rpm pump speed at idle in gear. That's close to 1:1. The pump maximum rpm should be kept below 5600 for sure. So 1:1 works out ok on most engines. I think the peak output of the pump is before 2000rpm, so turning faster than 2000 doesn't really help, but is necessary to get the slow speed and idle to work. That's the pump stuff in a nutshell.
Whiteknuckle
I prefer full hydraulic, but I understand the cost effectiveness and "mechanical" hookup as being strong advantages of the cable setup. An improperly installed full hydraulic is probably worse than a well done cable system, but I still prefer the full system overall. Like most things in life there are pro's and con's to both.

boatn70

this is great input, anyone have some installation drawings to further show how all this gets hooked up and used???

Whiteknuckle

Falcon,
Here is a really really dumb question. On a car with variable power steering assist where the faster the engine turns the less power steering assist you get, how does that work? Is it on some kind of a clutch that turns the pump faster at low RPM? It would seem that could be what we are looking for at low engine speeds at idle for more assist!

nauti-buoy

Sorry I didn't help on my last post let me try again. If you were to go out and grab the cavatation plate on a cable system and jerk it back and forth with your hand you would have about a two to three inch movement(back and forth/slop) in the drive. if you are running down the river/lake and hit a wave or set of boat wakes in any other position than perpendicular to the wave; the boat has a tendency to jerk to one side. Hydraulic steering helps tremendously in this situation. There is absolutely no play in the drive with hydraulic steering, which helps with the tracking of your boat in rough water situations and hitting waves on an angle. Also if your boat chine walks at high speeds it can be dangerous with a drive that has steering play in it. Hope this post helped better.