OE Hydraulic Steering No Assist
 

Circa 1996 OEM cable actuated hydraulic rack via helm and hydraulic PS Pump on 7.4 LX MPI twins in front of B1's.

From one outing to the next the steering felt as if it had no power assist. I spoke to my mechanic about it and after sending him a video of the fluid in the PS reservoir he noted there wasn't enough "disturbance" and the pump was bad. I replaced and bled the pump as per the repair manual, the reservoir required about and inch of top off which to me signals the pump is moving fluid. Today on the water the steering doesn't feel any better. It's generally hard to steer in either direction the past two outings but the below is what really grabbed my attention and alarm for concern.

While on plane the assist feels great turning left, but when turning right (to straighten from) a left hand turn I have to grab the wheel with two hands and yank it back to middle. When turning right and then steering left (to straighten out) there is "normal" assist feel. The manual reads "hard steering to starboard- cable too long or restricted", "hard steering to port-cable too short or restricted."

Is it a matter of the internal cable workings simply binding between outings due to age or should I be looking to the rack and or helm as well?

Thanks for any help you can lend!

Keith

Marine/boat power assist steering is not the same as auto power steering, It will only assist when a load is applied to the actuator normally when on plain. If it's stiff when docking/going slow it would tend to be the cable or helm. Disconnect the pin from the actuator to the drive arm linkage and see if the drive moves free.

The cable moves a shuttle valve in the rack (control valve). The valve doesn't move much, but this movement causes the hydraulic pressure into one side or the other of the piston. If the cable is loose or the slots are not vertical (item d in top right pic) then flow is restricted

https://cimg1.ibsrv.net/gimg/www.off...3724c049b8.jpg

While not on plain the steering feels tight (compared to all outings before last 2) when going slow and docking but not nearly as bad as I mentioned above about being on plain and turning right.

So disconnect the pin between the rack and drives to take the drives out of the equation? Fire the engine and work the steering while on the trailer to see if it feels more free? If it feels the same I'm looking at rack, cable or helm?

Keith

Thanks I'll check the cable for being tight and properly aligned. For what its worth I did nothing with nor near the cable to change its orientation since the issue started.

Keith

The cable was tight; however, the (D) Cable Guide Tube slots were positioned at 1 o'clock (toward the transom) in relation to the rack. I loosened the steering cable nut and oriented the Cable Guide Tube to 12 o'clock. I guess it's time for a test drive.

I did notice the Cable Guide Tube moves about 3/4" within the rack when changing direction from left to right and right to left steering at the helm. Is this motion normal?

Thanks for your insight
Keith

if you can get to it, disconnect the cable from valve at transom, see how it turns not running, should be smooth both ways. If sticky and binds replace the cable, if not the valve is bad(which I'm betting form how you described

PM sent

I converted my steering to full hydraulic, so I have a perfectly good shuttle valve sitting on my workbench. If you're interested make me an offer, it's not doing me any good.

1. Did the above and the steering wheel moves without issue (both directions) so we can rule out the cable and helm.

2. Started the boat yesterday (on trailer, steering system fully connected) with the cable guide tube slots vertical and the steering is still overly stiff to starboard.

I still haven't removed the pin to the tiller arm to rule out drives binding but as stated above, with the engine off the steering wheel moves equally and freely in both directions. The issue only seems to present itself when the power steering system is in operation while the engine is running and again only when steering to starboard.

At this point and as most mention above, the issue most likely lies in the Control Valve Assembly on the rack.

Keith

I'm leaning your way, but could also be the pump. If you can let go of the wheel and it doesn't immediately start turning to port, then probably the rack, but if it does then might be the pump. If you have some hydraulic gaguges you could check the pump

Thanks, as described above the pump is new and the steering behaves the same as with the old unit.

The boat tracks straight on plane and off when I let go of the wheel while on the water. On plane the steering wheel has to be wrestled right, idle speed and on trailer much heavier steering to the right.

Would the control valve be the only failure point of the rack or can the steering cable tube come into play as well? I ask as a member above mentioned they have a control valve and figure that would be much easier to replace than the entire rack.

Keith

The control is a shuttle valve which slides one side or the other as the cable is moved. If the valve moves easy and there are no internal leaks, then it should slide either way easy. I have not tried to replace just the control, think its easier (for me) to replace the rack.

https://cimg3.ibsrv.net/gimg/www.off...c9e0f4c376.jpg

Thanks for the schooling!!!

I purchased an entire new rack. No reason to take a chance. I only have the Merc. Manual #1 and Claymer which are both engine and stops with the PS pump.

Is there a dang pivot bolt attaching the rack at the bottom as well as the one staring me in the face on the top? I sure hope not :(

​​​​​​​Keith

Your correct only the one.
The hardest part to remove/install the rack is the tabs that keep the top and bottom bolts in place. Those tabs need to be beny clear to remove, and bent back in place to secure. The pivot bolts do not go clear thru

Keith, Look at a paint can opener about a buck ($1.00) and I think you can get the tab started. Once it is started it is fairly easy to finish opening it up, laying it flat. The bolt is not tight no worry there.

Keith, did you pick up the Teague take off?

Got one, Home Depot gives them free with paint now!

Mechanic buddy didn't help today as it rained all day. Hesitant to call the boat mechanic because he makes a huge grease mess for me to clean each time and will probably just let the power steering fluid drain in the bilge, ugh!!


I don't have alot of SAE tools as all of my previous wrenching experience has been with metric.
Does anyone know the size socket needed for the pivot bolt heads.

Steering
 

1 inch just backed out lower bolt e nuff to pull unit it was ruff but doable

Held off on doing the rack this weekend as I wanted be sure the re-man pump I installed wasn't the issue. It wasn't; therefore, next weekend NOS rack it is, as I feel I've ruled out everything else. After 3 pumps including the original, all the below has stayed the same after the bleeding process in the manual and with the steering tube slots on the rack properly orientated. The rack is also moving freely on the pivots with all linkage removed.

1. Drives disconnected from tiller arm = I can move both with my thumb using the tiller arm!! Definitely not a problem in the gimbals.
2. Drives disconnected from tiller arm, engine running, on trailer= the steering feels the same as OP, harder in general much more so to right.
3. Everything connected, engine running, on trailer= same as #2 above.
4. Everything connected, engine running, on water at idle or plowing= same as #2 above.
5. Everything connected, engine running, on water, on plane, at 3k rpm= same as #2 above and have to yank the wheel hard to the right to turn, left is "normal".
6. Steering cable disconnected from rack, engine off, boat on trailer= free steering.

In speaking with the mechanic I use (has 30 yrs. experience), he's never seen an issue like this be the rack and is why I went with a known good second hand pump from him. The only rack failures he's seen is leaking seals. Now the manual does read, "Hard steering/no assist= Actuator spool valve (shuttle valve in post #13 above) sticking and/or control valve leakage (piston in post #13 above)." That's what I'm banking on, fingers crossed. The good thing is only one bolt retention tab is bent against the bolt and it's the easiest to access.

Keith

FIXED!!

It seems the NOS rack (actuator) fixed the original no assist issue. Today on the water was the first time I've seen the PS fluid churning in the reservoir on any of the three pumps I tried. I had full assist in both directions, no hangups as originally posted. I also noticed when turning the wheel on the trailer the steering cable tube slots on the new rack stayed put in the 12 O'clock position. On the original rack the tube would turn toward the bow and the slots would wind up at 11 O'clock.

The return fitting at the rack broke and I fixed with a brake hose flare fitting and bend which would probably be fine but I only had 3/8" coolant hose on hand. There's also a clamped connection at the flair as well as a 3/8" mender and I'd rather run as little mends as possible. I found a used OE fitting and line that I'll replace it with when it arrives.

Hope this update helps someone in the future!!

No back to my regularly scheduled program of trying to find why the SB engine surges intermittently off idle.
https://www.offshoreonly.com/forums/...-please-5.html

Keith