22275073 Pump Piston | Genuine Volvo Penta Part

🔧 Product Description

The strength required to steer a boat with a hydraulic steering system is inversely proportional to the number of turns of the wheel lock-to-lock. Wheel turns are determined by the ratio between the cylinder volume, the pump displacement and the free movement of the steering device. A large cylinder volume with a small pump displacement gives more wheel turns; a small cylinder volume with a large pump displacement gives fewer. Fewer wheel turns means quicker steering response but more effort; more wheel turns means slower response but less effort. The helm pumps are available in three displacement sizes - 28 cc, 33 cc and 39 cc - each in three mountings: front mount, rear mount and tilt mount. This is the 28 cc rear mount pump, with 5 pistons, a 70 bar relief valve setting and a maximum wheel diameter of 711 mm.

⚙️ Key Features

• 28 cc displacement per wheel revolution
• Rear mount
• Five piston pump
• 70 bar relief valve setting
• For steering wheels up to 711 mm in diameter
• 5.879 kg
• Replaces 21639573
• Rear mount helm pump
• 5 pistons
• Maximum wheel diameter 711 mm
• 5 kg
• Displacement per rev: 28 cc
• Max wheel diameter: 711 mm
• Pistons: 5
• Mounting: Rear mount helm pump
• Relief valve setting: 70 bar
• Weight: 5.879 kg
• Fits: Volvo Penta hydraulic steering systems

🔌 Function

Converts steering wheel rotation into pressurised hydraulic oil flow to the steering cylinder.

⚠️ Common Signs of Failure

• Heavy, notchy or inconsistent steering
• Wheel turning without the drive following, from internal bypass
• Hydraulic oil weeping at the shaft seal or the port fittings
• Air drawn into the circuit giving a spongy helm

🛠️ Service Notes

• Mounting is the first thing to match: 22275070 is the same 28 cc pump in front mount and 22275076 in tilt mount
• The nine pumps in this range differ only by displacement and mounting, so order by those two figures rather than by appearance
• Bleed the circuit fully after fitting and check the level with the steering held hard over each way
• Displacement and mounting together are the product: the same 28 cc displacement is also listed as 22275070 and 22275076, and the other rear mount pumps are 22275074 and 22275075
• Tilt mount pumps are rated to a 508 mm wheel against 711 mm for the front and rear mount pumps
• Cylinder volume and pump displacement together set how many turns the wheel takes lock to lock

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 22275073 → Supersedes 21639573 → Supersedes 21135048

OEM / Related Numbers

• 21639573 earlier number superseded by this part
• 21135048 earlier number superseded by this part

📦 Condition

• Genuine Volvo Penta part
• Brand new
• Supplied in original or equivalent packaging