Hydraulic steering system too small ??

[Vronsky]

I have a 20 feet motorboat (Jeanneau Merry Fisher 605) with a Suzuki DF115A OB (max size).
I replaced the original cable steering with a Mavi Mare hydraulic kit GF150BRT with a pump flow rate of 17cc (hd/hd turns: 4.5) and a steering cylinder of 83cc. This kit was advertised to handle max 150HP engines, so more than enough for a 115HP.

After installation I noticed stiff heavy steering and squeaking noises from the pump, which hasn't gone away since. Mavi Mare claims this squeaking noise is normal..The former cable steerin actually has turned out more agreeable....

Comparing this Mavi Mare kit with eg. Baystar HK4300, also max 150HP, this Baystar offers a pump of 23cc (hd/hd turns: 5.3) flow rate and a cilinder capacity of 120cc >> a significant difference in specifications.

I'm wondering if the Mavi Mare system might be too small after all.

Any thoughts??

Thanks,
V

 

[kapnD]

Hoses too small?

 

[Vronsky]

Thanks.
5/16" hoses, a step up from the 1/4" size, should be good.
Contacted the dealer, but I'm out of warranty period.

 

[baeckmo]

That steering should be adequate for normal use, it works with higher pressure and lower flows than the Baystar.
First, before anything else: detach steering bolt in engine's tiller arm. That allows you to check if it is the engine swiveling or the steering that causes stiffness. If both move easily when separated, then there is something jamming the tiller link movement. The noise is a sign that there is air in the oil; read manual for de-aerating procedure.

Hose dia is normally only a problem in cold climate, when oil viscosity increases, but if a hose is damaged by a sharp fold (happens when installed with too small radii), there is an increase in resistance.

 

[fallguy]

I don’t know the specifics of the Mavi Mare system. Baeckmo gives lots of good advice. I had a problem with my original design (Dometic), and the issue was my reservoir tube was too short for adequate supply and ease of bleeding. Bleeding is critical and I purchased a bleeding system sold put of Florida and resolved my reservoir issue by moving the intake to a higher location on the helm station and repurposing the hole for a phone holder.

it may not apply to you, but may help others landing this thread in searches

 

[Vronsky]

That steering should be adequate for normal use, it works with higher pressure and lower flows than the Baystar.
First, before anything else: detach steering bolt in engine's tiller arm. That allows you to check if it is the engine swiveling or the steering that causes stiffness. If both move easily when separated, then there is something jamming the tiller link movement. The noise is a sign that there is air in the oil; read manual for de-aerating procedure.

Hose dia is normally only a problem in cold climate, when oil viscosity increases, but if a hose is damaged by a sharp fold (happens when installed with too small radii), there is an increase in resistance.

Thank you. Indeed checked engine swivel detached from the cylinder: movement was easy, as well as wheel turning.
System has an 83cc cylinder, and a 17cc pump. Other brands with similar configs -like Ultraflex- specify a max HP rate of 115, not 150.
Bled the system many times following procedure in manual.

Here's a link to a video clip of the noise (hope it works) >
Dropbox https://www.dropbox.com/scl/fi/nzol3vcq3tupk6c0qvavf/PXL_20250718_145509865-kopie.mp4?rlkey=s75q8by0oakixu8x9cow2fbr1&st=n3umm0et&dl=0

V.

 

[baeckmo]

Was that clip recorded with the cylinder connected to the engine tiller arm? Please add a photo of engine side showing cylinder and linkage.

 

[Barry]

While the volume of the cylinder divided by the displacement of the pump per revolution gives the number of turns for the full stroke of the ram, it does not relate directly to the force that
the cylinder will put out.

The diameter/area of the cylinder (less the ram diameter/area) determines (for a given input pressure) what the output force results.

Not sure how you would find this specification out.

Also, if input torque to the wheel, ie what you feel you have to put out to get a comfortable feel for a turn is too much. You could increase the diameter of the steering wheel.
Additionally, the addition of a "suicide knob" makes a big difference as well.

 

[baeckmo]

Difficult to hear, but the squeeking sound when you rotate the wheel sounds like rubber "rubbing" dry against a metal surface. Try to give the wheel shaft and the cylinder ram a few drops of hydraulic oil. The rattling when you rock the wheel is the locking valves in the pump outlet; they normally give a click when a steering manouver is ended; your rocking habit is not "normal procedure".

As I stated in note 4 above, and better explained by Barry, the cylinder and pump displacements are NOT per se related to the steering capacity, as referring to engine size. You can come up with smaller or larger units as well; it is only a question of correct mechanical dimensioning. That said, and your statement that the engine and hydraulics move easily when separated tells me that there is an installation fault that causes jamming. This is why I want to see what the setup looks like IRW.

 

[Vronsky]

Thanks.
Here are some pictures of the engine side, all work smoothly, no noises.
Dropbox https://www.dropbox.com/scl/fi/efehtwpr5wx52gfxexpkx/PXL_20220915_103712261.jpg?rlkey=v4k2ete1vjnv9o0ktnoo71pgv&st=ttw2saiz&dl=0
Dropbox https://www.dropbox.com/scl/fi/0uloc8juzchc7dt5j0ye8/PXL_20220915_103704478.MP.jpg?rlkey=eykxay0fsm47o0xk4ree3sq7n&st=u12xsj5k&dl=0
Dropbox https://www.dropbox.com/scl/fi/4beyc6wlwq9z0nlz5enui/PXL_20220915_103730905.MP.jpg?rlkey=evuafb3gqu2t1y3a40ewqf4au&st=vddl1fxh&dl=0

For comparison, here's a video of a Seastar pump, a bigger capacity but otherwise mechanically identical to my Mavi Mare: sure wish I had this one on board >
Dropbox https://www.dropbox.com/scl/fi/xhggon3pjak3q6u750zc9/Pompa-idraulica-Seastar.mp4?rlkey=35s7gmp44dtywn8ja0z6znmtv&st=p2mripub&dl=0

Oiling the wheel shaft is a good idea.
Current wheel is 14"; a bigger one would surely help but not much room available at the steering position for a bigger one.

The bore of the MM cilinder is 27mm, same as many other competitive cilinders, but the rod of the MM is 16mm which is twice as thick as others, and this significantly reduces the cilinder capacity, and so explains the smaller capacity pump.

 

[baeckmo]

Ok, next level: is the link between cylinder and tiller arm moving freely when attached (asking because I've seen them bolted tight...). Does the cylinder rotate freely in the engine bracket tube, when changing engine trim? Is the stiffness equally stiff while engine idling as when speeding, and is it equally stiff both ways?

 

[Vronsky]

Thank you.