Mercury Jet 25 Manual Download Page 28 | Manualshive

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TROUBLESHOOTING

24

Engine Over‑Speed (Excessive RPM)

POSSIBLE CAUSES

• Outboard mounted too high on the transom.
• Worn jet pump impeller or liner.
• Incorrect jet pump impeller clearance adjustment.
• Tilting the outboard out beyond a vertical position.
• Cavitation of the impeller due to rough water or obstruction in

the boat hull.

• Blockage of the water intake.

Performance Loss

POSSIBLE CAUSES

• Throttle not fully open.
• Damaged impeller.
• Incorrect engine timing, adjustments, or setup.
• Boat overloaded or load improperly distributed.
• Excessive water in bilge.
• Boat bottom is dirty or damaged.

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Summary of Contents for Jet 25

Page 1: ...i 2008 Mercury Marine 25 Jet 2 Stroke Supplement 90 10257081 507...

Page 2: ...ii...

Page 3: ...g In Freezing Temperatures 11 Pre Starting Check List 11 Operating In Salt Water Or Polluted Water 12 Operating In Shallow Water 12 How the Jet Drive Operates 13 Stopping the Boat in an Emergency 14 S...

Page 4: ...TABLE OF CONTENTS iv TROUBLESHOOTING Engine Over Speed Excessive RPM 24 Performance Loss 24 ENGINE INSTALLATION Determining the Mounting Height of the Outboard 25 Water Testing 26...

Page 5: ...is only occasionally used for such purposes The repair or replacement of parts or the performance of service under this warranty does not extend the life of this warranty beyond its original expirati...

Page 6: ...ty service Warranty claims shall be made by delivering the product for inspection to a Mercury dealer authorized to service the product If purchaser cannot deliver the product to such a dealer written...

Page 7: ...g system by a foreign body running the engine out of water mounting the engine too high on the transom or running the boat with the engine trimmed out too far Use of the product for racing or other co...

Page 8: ...IMITED IN DURATION TO THE LIFE OF THE EXPRESS WARRANTY INCIDENTAL AND CONSEQUENTIAL DAMAGES ARE EXCLUDED FROM COVERAGE UNDER THIS WARRANTY SOME STATES COUNTRIES DO NOT ALLOW FOR THE DISCLAIMERS LIMITA...

Page 9: ...nd reverse thrust will minimize boat movement the boat may tend to move slowly forward or backward This is normal for a direct drive jet driven boat The operator should be aware of this and use cautio...

Page 10: ...in the understanding of a particular step or action Protecting People In The Water WHILE YOU ARE CRUISING It is very difficult for a person standing or floating in the water to take quick action to av...

Page 11: ...wing suggestions Use flotation devices Have an approved personal flotation device of suitable size for each person aboard it is the law and have it readily accessible Do not overload your boat Most bo...

Page 12: ...as sand shells seaweed grass tree branches etc can be pulled in by the pump This may not only block the water flow and cause lost of steering control but can be expelled from the rear of the pump as...

Page 13: ...cement Specifications Model Jet 25 Jet power 19 kW 25 hp Horsepower 22 kW 30 hp Engine idle RPM 950 25 RPM Full Throttle RPM range 5150 5850 RPM Number of cylinders 2 Piston displacement 429 cc 26 3 c...

Page 14: ...29515 a Top cowl b Manual start handle c Throttle grip d Gear shift e Lanyard cord f Reverse lock lever g Tilt pin h Jet drive housing i Water intake housing j Reverse gate k Water outlet l Driveshaft...

Page 15: ...e is clear Pre Starting Check List Operator knows safe navigation boating and operating procedures An approved personal flotation device of suitable size for each person aboard and readily accessible...

Page 16: ...ter intake can be greatly increased by avoiding the intake of sand and gravel The intake suction will act like a dredge when the water intake comes close to the bottom It is better to stop the engine...

Page 17: ...moves over the outlet nozzle to direct the water in the opposite direction a c b 29022 a Water intake b Water outlet nozzle c Reverse gate When the jet drive is in neutral the impeller continues to ro...

Page 18: ...stopping capability unique to this form of propulsion WARNING Using the emergency stopping capability of a jet drive unit will slow down the boat in an emergency However sudden stopping may cause the...

Page 19: ...ch or plugging the water intake to the jet pump Use caution when maneuvering at high speeds in areas where debris weeds logs gravel etc could be picked up into the jet drive The ability to take evasiv...

Page 20: ...e the engine must be shut off and debris physically removed from the grate Clearing A Lodged Impeller WARNING Rotating the flywheel to free a lodged impeller can accidentally start the engine resultin...

Page 21: ...arpen or alter the top side lifting angle Check the impeller blades occasionally for damage Use a flat file to resharpen the leading edges Sharpen to a 0 8 mm 1 32 in radius by removing material from...

Page 22: ...Check the impeller clearance by sliding a feeler gauge through the intake grate and measure the clearance between the impeller edge and liner If adjustment is required refer to Impeller Removal and In...

Page 23: ...peller always turn the ignition key or lanyard stop switch to the OFF position and remove the spark plug leads from the spark plugs while servicing the impeller 1 Shift the outboard to the neutral pos...

Page 24: ...se on the shaft until the keyway is directly above the flat on the shaft This will free the jammed key and allow removal Shift Link Rod Adjustment WARNING Pressurized water hitting the reverse gate ma...

Page 25: ...tral Pull on the reverse gate by hand to verify a b c d 29084 a Shift link rod b Shift cam c Roller d Reverse gate ADJUSTING SHIFT LINK ROD 1 Place the shift handle into full forward shift position 2...

Page 26: ...e Driveshaft Bearing Lubricate the driveshaft bearing before each use Tube Ref No Description Where Used Part No 95 2 4 C with Teflon Driveshaft bearing 92 802859A 1 IMPORTANT It is important not to u...

Page 27: ...re Visually inspecting the purged grease at this time will give an indication of conditions inside the bearing housing A gradual increase in moisture content indicates seal wear If the grease begins t...

Page 28: ...ent Tilting the outboard out beyond a vertical position Cavitation of the impeller due to rough water or obstruction in the boat hull Blockage of the water intake Performance Loss POSSIBLE CAUSES Thro...

Page 29: ...ondition should be avoided by proper height setting Installing the outboard too low on the transom will allow excessive drag BOATS WITH A V BOTTOM HULL 1 Measure the width of the leading edge on the w...

Page 30: ...revent cavitation at running speeds When operating the boat the outboard driveshaft housing should be vertical or tilted toward the boat when planing to provide a scooping angle on the water intake Ti...

Page 31: ...a rough water plate A rough water plate may be helpful in reducing cavitation when running in windy rough water conditions where air is sucked into the water intake when jumping waves Install a 0 8 m...

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