Maximum Hydraulic Pressures
 

I know we have some experts here so here we go!

What is the maximum pressures developed or used in the three hydraulic system of boats?

Trim (Bravo w/ Prestolite pump)-?

Steering w/Mercruiser Power steering pump w/Latham steering?

K-Planes with Mercruiser tab pump?

I am building some replacement lines & need to know the pressures involved.
Thanks!:)

I think the power steering is 1200 psi.

I think the power steering is 1200 psi. I don`t know why, but for some reason Mercruiser decided to pur 600 psi hose on mine! That lasted for a while but ruptured while I was out on Lake Michigan. I took it off and had a local Hydraulic repair shop make a good one to replace it with.

Never really worried about it. -4 and -6 S/S lines are rated at 1500psi or above. Never blew one.
I do know my aftermarket steering rating from the relief valve was 1100 psi.
Gary

I belive the k-plane and trim system are around 600psi.

Thanks Guys, That is about what I thought the pressures were. I just hated to have hoses built & like above, have one burst where it is secured UNDER the engines!. I now feel I can avoid that with certainty.:)

Trim I/O cylinder and trim tabs are 400 PSI. When replacing the tab hoses last year I could not find any in the 400 to 600 psi range. The rating jumped from 250 to 1200 or 1500.

From Boston Rubber I learned that hose burst pressue is 4 times the working pressure. So the 250 psi hose had an unstated 1000 psi burst pressure. Using 250 psi hose at 400 was at less than 50% burst of burst. With those margins I felt 250 was a safe way to go.

With the known pressures now, has anyone ever built there own hoses using Earls or JIC type fittings???
Is this practical?

For stock Mercruiswer stuff the steering is 1200 PSI on the high side, 100 PSI on the return. Oildyne pump is set at 2200-2600 PSI high side (up on drive, down on tab- blue wire hot) and 400-600 PSI on the low side. The older Prestolite pump was higher.

The Bennet type tabs have a much lower working pressure, not sure what it is.

I don't like stainless hose for steering as 1 nick in the braid and the pressure capacity is gone, and as far as I know the stainless/teflon hose is the only one with the proper rating, the regular stuff with anodized fittings is not rated that high.

For steering you want a hose with an SAE rating, I can't remember the number but your favorite hose supplier will know, 100R rings a bell.

use any SAE R1 hose its rated at 2200 psi working psi and 8000 burst psi,its also coast gaurd approved for hydraulic use

BAM & Alf of pressure. I guess thats why the steering hoses are so big. Both the Bravo trim & K-Plane pumps appear to be the same except for the reservoirs... one is plastic & one is a "tincan". The motors and pump assy seem just alike. Where is the pressure difference generated????

The psi differance is controlled by the relief valve in the pump,and is set by cylinder size,and by thepsi the cylinder can safely work at.