HPJunkie

I have a dual ram single drive imco steering set up on a boat that I purchased used. The problem is that the steering is not as responsive as my single ram Wpm unit on my last boat. My wpm unit felt tight and responsive like a tight outboard setup and was relativly quiet, the Imco on the otherhand feels like an old car Kinda of sloppy and spongy and it does make some squishing sounds at the helm that sound like maybe some air is in the lines. Do I need a reservoir for 2 rams? My helm unit is a 120cc do I need a 160 cc. unit? I have drilled out the orfice in the pump, that did help (15%) i'd say. It is the same pump just a different boat. Any insightwould be helpfull. Greg

Falcon

You have air in the system and it needs to be bled out. There are several methods to do it, but I would give IMCO a call about the procedure they recommend. The extra cylinder volume and extra lines (if you went from a cable system to a helm) entraps a lot more air. There isn't enough cylinder stroke to push all the air back to the helm where it would get routed back to the reservoir line to purge out, so there is the potential that some air will never get out of the right and/or left lines which causes the softness in your steering. You can tell if you have a fair amount of air in the system if your reservoir level rises significantly after the engine is shut off. When the pump is running it compresses the air in the lines so the level drops. A slight level change is normal because of the expansion of the hoses under pressure (I know it seems like a small amount, but there is a lot of line in a helm system).
The ITS now has bleeder valves on the R & L line connection block to make it easier to bleed. They even have a new procedure which details how the system can be prefilled to prevent foaming of the oil. Foaming is difficult to prevent if you don't have a reservoir large enough to fill the lines when you first start the engine on a new installation. The pump goes dry before you can get more fluid into it and it starts to pump air into the oil (foam!). Once you have foamed oil, bleeding doesn't work until the air has a chance to settle out.
Well, enough rambling on! Good Luck!

HPJunkie

Falcon,
Thanks for the reply. That makes sense. Do you think that adding a reservoir will solve the problem by itself?Greg

Falcon

No, although it can make it easier to keep the oil from foaming on the initial fill and run. It is simplest to think of a hydraulic helm power steering system this way:

1)There are 2 main hydraulic circuits

a) The supply circuit, reservoir > pump > helm > cooler > reservoir, which is always circulating oil (well, except at steering lock!). This circuit can self bleed because the air pushes back to the reservoir. A larger reservoir "can" help this self bleed because you "may" have enough fluid on initial startup to avoid running the reservoir dry and pump air back into the system and foaming the oil. If the system is filled and bled properly, a larger reservoir is not necessary unless your steering system geometry is affected by trim angle (twin ram, twin drive, one drive up, the other down, not recommended, will usually break one of the plastic thrust pads off when it enters the gimbal ring!).

b) The steering circuit, Port(L) < helm > (R)Stbd, which only moves oil when the helm turns.

2) Now, when you turn the wheel to stbd, ports change in the helm to allow feed from the supply circuit (pump) to route to the steering circuit through the g-rotor in the helm to the stbd(R) line and to the appropriate cylinder port(s). When the drive starts turning, oil is returned from the other cylinder port(s) to the port(L) line at the helm. This oil is routed through the helm to the reservoir(T) port, through the oil cooler and back to the reservoir.

3) If there is air in the steering circuit, some will probably get back to the helm and get pushed back to the reservoir to burp out. The problem is that on most boats, there is enough line length and cylinder volume that you will probably just have an air "slug" moving back and forth somewhere in each right and left steering line/cylinder. This slug of air is what I said "compresses" when the pump is running, lowering the fluid level, which then rises again when the pump stops turning. Without getting too much more technical, this happens between the 2 circuits because there is some slight leakage between the 2 circuits in any helm.

4) What most bleeding procedures try to accomplish is pushing oil out each steering line until there is solid oil. The Merc ITS does this through little brake bleeder style valves on the steering line connections. These bleeders are inside the boat and you can connect a line to them and run them back to the reservoir, no lost fluid, very little mess. Some of the other manufacturers have you turn the wheel (engine off) until the cylinder is bottomed, remove the external line connection closest to the piston, then turn the wheel slowly in the opposite direction until you have solid oil coming out that line, watching the reservoir level. Reconnect the line. Repeat for the other lines and steering direction. Because the cylinder is bottomed, very little air can be in the cylinder on that end of the cylinder. When you get solid oil in the line, most of the air is removed, for that line/cylinder direction.

5) Helm displacement size: The amount of fluid displacement per revolution. This determines the number of turns lock to lock for a given steering cylinder setup. Most systems are setup for 3-4 turns lock-lock.

6) Orifice Size This controls pump flow, mainly improving things at slow pump speeds. It can only help so much, don't go too far. RPM helps more (pulley size). Remember how the steering circuit connects to the pump output?. If there isn't enough pump pressure/flow, it will only let you turn the wheel as fast as the pump can supply fluid (well, it does switch to "manual bypass" in the helm, but it's so hard to turn, it feels like you hit a steering input limit). If engine speed drastically helps steering at the dock, you have a supply problem. Check the filter, if there is one!

Now that I have written a book on the subject, let me know what you find.

US1 Fountain

iTrader: (1)

Last yr I had to disconnect one of my lines for engine removal. Now whenever I go to full lock, the helm sounds like it is aireated. No sound comes from it during any other time. A friends boat makes no noise at full lock. I had to removal the motors right after I bought it, so I don't know if the sound was there before hand. Does these sound like air or is it normal? Seems to work fine otherwise.
Thanks

Payton

A few companies do recomend that you have a resivior with a dual ram system. You simply mount it above the pump and have a line fedd down to the pump cap.

Cord

iTrader: (2)

I also have a dual ram system. I found that the stock reservoir did not have enough capacity and would overflow when burped.

Falcon

I think the extra reservoir is a plus and may be necessary with most dual ram, twin drives, but I have seen systems work fine without it (you must get it bled out properly). One thing to keep in mind with the extra reservoir, if the main reservoir isn't full and you put the extra one in, it can leave an air bubble in the main reservoir. The small lines used to connect between the cap and the extra reservoir will not let oil and air pass by each other thru the hose. To fix this, just loosen the cap on the main reservoir and let the air out. Tighten the cap up when full.
Cord, when you say "burped" do mean air returning to the reservoir or just hitting the steering stops and getting that quick volume change when the lines expand and contract from the high pressure spike? How much this spike changes volume can depend on the type of high pressure lines used, the stiffer the better.
When the air is fully bled out of the steering, the reservoir level should stay fairly constant. You can tell when the system is bled out. With the engine(s) off, you should have very little movement side to side when you push on the drives. With the engine(s) running, there is some pressure in the system which can make things feel solid outside even with air in the system. Cable systems may have a little extra with the movement of the internal valve.

Cord

iTrader: (2)

I could not bleed the system. When the engine was running the level would fall and suck air. You fill it and when the engine was shut off it would overflow. The reservoir solved that problem.

Falcon

It can be done without, but I know it is better to have the extra capacity.

Getting back to his original post, I don't think the extra reservoir is the main problem. The reservoir could help, but he has to bleed the air out. I have heard way too many think that they can get away with just filling and turning the wheel back and forth. Cable system lines from the cylinders are relatively short and it may work on them to get most of the air out just by cycling back and forth, but full hydraulic helm setups require a bleeding procedure of some type.

There are methods to fill and bleed the hydraulics without running the engine(s) which can keep from running the reservoir dry. I prefer these methods, wether you have an extra reservoir or not.