MerCruiser 350 MAG User Manual (English)

Questions and Answers:

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Briana WilliamsAug 13, 2025
Why my MerCruiser 350 MAG will not start?
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  Jeremiah MorrisonAug 13, 2025
  If your MerCruiser Engine won't start or is hard to start, consider the following: * Check the lanyard stop switch. * Review the correct starting procedure. * Ensure there's sufficient fuel supply by filling the tank or opening the valve. * If you suspect a faulty ignition system component, service the ignition system. * Replace the fuel filter if it's clogged. * Drain and replace stale or contaminated fuel with fresh fuel. * Inspect fuel lines and the tank vent line for kinks or clogs; replace kinked lines or clear obstructions with compressed air. * Check wire connections. * For EFI system faults, have it checked by an authorized Mercury MerCruiser dealer.
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Jennifer ElliottAug 17, 2025
What to do if MerCruiser Engine runs rough?
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  Candice McconnellAug 17, 2025
  If your MerCruiser Engine runs rough, misses, or backfires, consider these potential issues: * Replace the fuel filter if it's clogged. * If the fuel is stale or contaminated, drain the tank and refill with fresh fuel. * Check for kinked or clogged fuel lines or the fuel tank vent line; replace kinked lines or clear obstructions with compressed air. * Clean the flame arrestor if it's dirty. * If there's a faulty ignition system component, service the ignition system. * For idle speed issues or EFI System faults, have the EFI system checked by an authorized Mercury MerCruiser dealer.
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Ryan BrownAug 21, 2025
How to troubleshoot a MerCruiser 350 MAG Engine that is not recharging?
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  Troy BarnesAug 21, 2025
  If your MerCruiser Engine is not recharging, here are a few things to inspect: * Turn off any non-essential accessories to reduce the current draw from the battery. * Replace and/or adjust the alternator drive belt if it's loose or in poor condition. * Test the battery and replace if necessary. * Check all associated electrical connections and wires (especially battery cables) for looseness, dirt, or damage; clean and tighten faulty connections, and repair or replace any damaged wiring. * Test the alternator output and replace if necessary.
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Elizabeth Mueller MDAug 28, 2025
What causes an oil pressure issue in a MerCruiser 350 MAG?
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  Tammy PughAug 28, 2025
  If you're experiencing an oil pressure issue with your MerCruiser Engine, consider these points: * Check and add oil if there is insufficient oil in the crankcase. * If there's excessive oil in the crankcase (causing it to become aerated), check and remove the required amount of oil, and identify the cause of the excessive oil (such as improper filling). * If the oil is diluted or of improper viscosity, change the oil and oil filter using the correct grade and viscosity oil, and determine the cause for dilution (such as excessive idling).
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James MillerSep 1, 2025
What to do if my MerCruiser 350 MAG Engine starter motor will not crank or cranks slow?
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  Mrs. Vanessa ShortSep 1, 2025
  If the MerCruiser Engine starter motor won't crank the engine or cranks slowly, here's what to check: * Ensure the battery switch is turned on. * Confirm the remote control is in the neutral position. * Inspect for any open circuit breakers or blown fuses and reset or replace them. * Examine all electrical connections and wires, especially battery cables, for looseness, dirt, or damage; clean and tighten faulty connections. * Test the battery and charge it if necessary, or replace it if it's bad. * Verify the lanyard stop switch is not activated.
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Brian LewisSep 4, 2025
What to do if the power trim motor does not operate on my MerCruiser 350 MAG?
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  Anthony PattersonSep 4, 2025
  If the power trim on your MerCruiser Engine does not operate and the motor doesn't run, check for these possible causes: * Replace the fuse if it's blown. Fuses may be located near the dash trim switch, at the trim pump, in the positive (red) power trim battery lead near the battery switch, or a combination of these. * Inspect all associated electrical connections and wires (especially battery cables) for looseness, dirt, or damage; clean and tighten faulty connections, and repair or replace any damaged wiring.
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Edward JonesSep 8, 2025
What to do if MerCruiser 350 MAG power trim motor operates but sterndrive unit does not move?
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  Jeffery ChapmanSep 9, 2025
  If the power trim motor operates but the sterndrive unit does not move on your MerCruiser Engine, consider the following: * Fill the trim pump with oil if the oil level is low. * Check for any obstructions if the drive unit is binding in the gimbal ring.

MerCruiser 350 MAG Specifications

General

Engine Type	V8
Horsepower	300 hp
Ignition	Electronic
Alternator	65 amp
Compression Ratio	9.4:1
Torque	330 lb-ft
Alternator Output	65 amp
Displacement	5.7L
Fuel System	Multi-port fuel injection
Cooling System	Closed cooling
Bore x Stroke	4.00 in x 3.48 in