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CDMA
04-29-2002, 11:19 PM
Now I know the difference and but why do we use one or the other. I see all these I/O boats running around with power steering ( either full hydraulic or partial) yet all these outboard guys just run with a helm that is a pump. I know a few Donzi's have been done like this as well. What are the advantages of either and why?

Chris

By hydraulic I am referring to a non engine assisted system like a teleflex sea star.

PaulO
04-30-2002, 08:37 AM
Torque steer is just as big a problem with outboards as it is with IOs. The reason you don't see power assisted hydraulic steering on outboards is that there is nowhere to mount the pump. OMC V8s had an engine mounted power steering pump for awhile but, no one else ever did it.
PaulO

CDMA
04-30-2002, 08:50 AM
Why not just use a helm pump on an I/O as opposed to the more complicated engine driven powersteering.

Chris

Kent Perroux
04-30-2002, 10:24 AM
I do use a pump for my helm. From the helm I have two hydraulic hoses going to a hydraulic (internal to the transom) ram. I am converting this to an external ram on the Bravo.

To add power assist is an option, but you also add additional weight and more things for the motor to turn.

The best is a Power Assisted Hydraulic helm, (three hoses), power steering pump, and external rams. This setup can run around $4,000.

There are many alternatives in-between.

CDMA
04-30-2002, 10:46 AM
Kent,

What you have is exactly what I am referring to. How does it / did it work and why don't more boats use it?

Chris

I really like the simplicity factor.

AVickers
04-30-2002, 04:47 PM
You wouldn't use it 'cause you wouldn't need it...You can steer an 18' Classic without power assist. What you need help with is the reactive torque steer that occurs when you quickly change the throttle position up or down -- which we tend to do often.

Power assisted steering can do one or both of two things: make the steering wheel easier to turn or make the steering quicker.

The Mercruiser system is power assisted and the system gets its original "I want to turn" signal via a cable just like the Teleflex deal. The control box -- mounted on the transom has a spool valve in it that will shunt fluid under pressure to one side or the other depending on the steering input. As long as it senses an off-center situation, it'll pump fluid until the ram "catches up" and it doesn't sense any need for more left or right motion. These systems do give you a sense of what's going on in that you can "feel" resistance and motion through the helm. This is a system that provides the captain with feedback.

Hydraulic helms are typically zero feedback... That means that you don't get that "rip-it-out-of-your-hands" feeling when you goose your small block in a 16' or, in your case, an 18' Classic. It takes the same power (or steering input), no matter what's going on back there and the helm WILL NOT MOVE if the drive is pushed side to side (if you really push it hard, there's a pressure relief valve in the helm that will pop off). You move the helm to the left, the pump moves some oil in an appropriate line that then pushes the ram to one side or the other. That ram is connected directly to the drive (in the case of an external system) or to the tiller (in the case of an internal system). As I said, if there is too much resistance to the motion of the helm, there is a pressure relief valve built in that pops off. If I remember correctly, this occurs at 5000psi on the Teleflex helms. Evidence that the system has "popped off" is that the steering wheel will change its position relative to the original setup (for instance, if you have the wheel centered when running straight and, after a pop-off, the wheel is 1/4 turn left when running straight...) If you need more "push" from the ram for a given pressure, you use a larger diameter ram -- same pressure distributed over a larger area gives more thrust. This will also give a slower response to the helm -- the ram will move less distance for a given number of turns of the wheel. After I installed my system and got the wheel centered, it never did change from this position -- thus, there was no over-pressurization of the steering system due to the forces generated by the drive trying to overcome the steering inputs.

Helm pumps are rated by the volume of oil, in CCs, they will move over one revolution of the wheel. Rams are rated by their overall travel and their diameter (which will determine the movement per CC of fluid being introduced to them...as well as the number of turns, lock-to-lock)

All this works into a formula that produces a system that has the power to move the outdrive back and forth at a speed that will allow the boat to be "responsive."

My Volvo needed a ram with a 7.5" throw. I picked up a 1.25" cylinder that had this throw and installed it with the low-volume helm from Teleflex -- at the time I was very worried about overcoming the thrust of torque steer. Turns out that it had plenty of thrust to control the outdrive -- known for its "rip-the-wheel-out-of-your-hands" torque steer. Unfortunately, although it was ok, I didn't consider it to be as responsive, or quick, as I would have liked... (The native Teleflex system was about 4.5 turns lock to lock. The Hydraulic Teleflex setup was just over 6.5 turns.)

Had I to do it over again, I'd install the highest-volume helm offered by Teleflex (about 25% more volume per wheel rotation, as I remember...). It still had the same pop-off pressure, so the drive wouldn't be able to move around on its own and it would be almost as quick as the original system.

GEOO
04-30-2002, 04:51 PM
Chris,
Most Hydraulic systems are made up of one of two Helms. A power helm or a manual helm (Char-Lyn, Campinalla)( spelling is Way Wrong). The Power Helms are better for high horse power and inbaords when a pump is easy to install. The manual helms are good for outboards and low horsepower inboards. The only problem is they are slow. 4-6 turns Lock to Lock.
I had a Latham manual full hydraulic system on my Volvo.
I drove a Twin Outboard Cat with an electric pump Hydralic system. Pretty Neat!! GEOO

Kent Perroux
05-01-2002, 09:36 AM
GEO, the reason you had 4-6 turns lock to lock is you were manually filling two large rams.

The internal rams are single, and are somewhat smaller. I have 3.5 turns lock to lock.

I really like the full power hydraulic systems. I have driven several high power boats with it. For an 18, a manual hydraulic is fine for most instances. I will stay with manual hydraulic on my upgrade, but a single external ram.

To answer the original question, most people like the feel of power steering and Mercruiser, along with the other stern drive manufacturers are trying to please the majority instead of the few with one system.

With hydraulic, you can take your hand off of the steering wheel at 60 mph in 3' chop without the boat trying to find it's own way. I would like to have the full power hydraulic (that Geo was talking about) but can't justify the price on an 18' boat. I'll save that for the race boat.

Craig
05-01-2002, 11:40 AM
Irecently put a hydraulic system on my boat (16' with Volvo 270) and it works great. With regard to price, I got one that I don't think anybody here has mentioned, a "Uflex" system. It is very much like what I think Teleflex calls their "Sea star" system. It truly is not lower quality, but I got all the stuff I needed for around $600.00 (maybe a tad more). The # of turns from lock to lock was a concern. I think that was a fuction of the cylinder length you requested. The manufacturers suggested, if the distance (3 of turns) was too high, to consider drilling a hole at a different position on the tiller (in the case of an older Volvo drive - like my 270). I actually ended up doing that and it's pretty comfortable now. Had to have a new mounting bracket made for the cylinder. Turned out pretty cool and the steering benefit is great. My wife and kids can drive the boat now without any trouble. It was previously very hard turning back to the left. The inherent torque steer problem of the old Volvo combined with aged manual steering cables had made it real bad prior to the conversion. Now its super.

Craig
05-01-2002, 11:46 AM
Oops! Previous reply has a confusing typo. Where I wrote "(3 of turns)" it should say "(# of turns)" Bad place for a typo!!

Donzified
05-01-2002, 08:27 PM
I went with Nynauntic pump and external ram.My internal tiller/steering fork on the volvol was worn out. If you have a volvol I suggest you go external ram. Make sure you match your pump with the ram, 3 to 4 turns lock to lock is good.The first time I mis matched and had 9 turn lock to lock . With the steering knob it was dock intertainment.It tracks true,leave it straight going down the canal and you can steer with the throttle,gas it go starboard ,let up, drift port.

AVickers
05-02-2002, 11:18 AM
My main concern w/ the purely hydraulic systems is that there is NO BACKUP! If a fitting or a line or ram seal gives out, you simply can't steer... What would an 18 w/a Small Block running full out be like if you suddenly and completely lost control of the steering???? eek! eek! eek!

At least with the MerCruiser system you have the cable... If you lose hydraulic power, steering would be very stiff, but it would still work.

Anybody else worry about this? :confused: :confused:

GEOO
05-02-2002, 05:33 PM
AVickers,
What happens if the cable breaks??? GEOO

Kent Perroux
05-02-2002, 06:36 PM
I did control systems for over 16 years in my past life...Hydraulics are much more reliable that cables, also more precise. I'll take Hydraulic before cable any day.

tailwind
05-03-2002, 10:08 PM
Hey Guys:

Interesting topic here. Am I correct in assuming my 91 "18" with the OMC King Cobra 350 has power assisted steering? I have a power steering pump on the front of the engine, with dual rams connected to the drive. If so, this system seems very adequate, as I can turn the drive with the wheel even when the engine is not running.

As for the fluid, Madpoodle is on the money - most any fluid will certainly work, even when mixed! Having towed sailplanes up to altitude with Piper 150 & 180 HP Super Cubs, and most favorite: Piper Pawnee 235HP, (Ag Plane), for over 20 years, we would routinely use Dextron automatic transmission fluid for the brakes etc., and not the mil spec AC stuff, no problems. Most of our tail dragger pilots only use the brakes for run-up only, as we were operating on a grass strip. For that matter, instead of running 100 octane AV gas, we would run 87 octane car pump gas from 5 gallon cans, and it really wouldn't make a difference. I could tow a fully loaded 2 seat sailplane up to say 2000 ft agl, and be back on the ground in position for another within say 5 minutes or so. That old Lycoming O-540 was and still is a great engine!

Best regards to all
Randy