MST MST Steering & Control Systems 2 — Questions and Answers
Question 1: When installing a new mechanical steering cable, the cable must be lubricated with what type of grease?
- Marine-grade grease compatible with the cable conduit material (Correct answer)
- Engine oil only
- Dry PTFE spray only
- No lubrication — cables must run dry
Correct answer: Marine-grade grease compatible with the cable conduit material
Marine-grade grease should be applied to the cable at the helm and cylinder ends to reduce friction and prevent corrosion.
Question 2: What is the correct method for measuring the helm effort (steering force) to verify compliance with ABYC P-17?
- Use a torque wrench or spring scale at the rim of the steering wheel with the engine running at rated RPM (Correct answer)
- Pull the cable at the engine and measure with a scale
- Measure amperage draw on the power-assisted helm motor
- No measurement is required — visual inspection is sufficient
Correct answer: Use a torque wrench or spring scale at the rim of the steering wheel with the engine running at rated RPM
ABYC P-17 specifies maximum allowable rim pull force at the steering wheel, measured while the engine is running at rated speed in forward gear.
Question 3: A boat equipped with Sea Star hydraulic steering has a cylinder that drifts off center when the helm is held steady. This symptom indicates:
- An internal leak past the cylinder piston seals or a leaking helm valve (Correct answer)
- Low oil in the trim reservoir
- A throttle cable misalignment
- Normal operation for hydraulic steering
Correct answer: An internal leak past the cylinder piston seals or a leaking helm valve
Cylinder drift (the engine slowly steering itself off-center) is caused by internal bypass past worn piston seals or a leaking helm steering valve.
Question 4: What type of fluid is used in most marine hydraulic steering systems?
- Automatic transmission fluid (ATF) or dedicated marine hydraulic steering fluid (Correct answer)
- Power steering fluid only
- Motor oil SAE 10W-30
- Brake fluid (DOT 3)
Correct answer: Automatic transmission fluid (ATF) or dedicated marine hydraulic steering fluid
Most marine hydraulic steering systems use ATF or a manufacturer-specified hydraulic steering fluid — consult the OEM manual for the correct specification.
Question 5: What is the function of the helm check valves in a hydraulic steering system?
- To prevent reverse flow from the cylinder back through the helm pump (Correct answer)
- To relieve excess pressure above system rated limits
- To filter contaminants from the hydraulic fluid
- To set the maximum lock-to-lock turns of the steering wheel
Correct answer: To prevent reverse flow from the cylinder back through the helm pump
Helm check valves block reverse flow from the steering cylinder to the pump, maintaining steering position when hydraulic pressure fluctuates.
Question 6: During a throttle and shift cable adjustment on an outboard, where should the cable end pin be positioned when the shift is in neutral?
- Centered in the shift lever slot with no tension on either end of the cable (Correct answer)
- Pulled to the forward stop
- Pushed to the reverse stop
- Position does not matter — only forward engagement matters
Correct answer: Centered in the shift lever slot with no tension on either end of the cable
In neutral, the shift cable end pin must be centered with no pre-load so the engine can fully engage both forward and reverse without binding.
MST MST Steering & Control Systems 2
When installing a new mechanical steering cable, the cable must be lubricated with what type of grease?