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Question

i have a 19 ft bayliner with (1998)mercury engine, when u give it full power, it idles from high to low, changing speed on its own. Any idea what''s wrong.

Submitted: 635 days and 10 hours ago.
Category: Boat
Value: $9
Status: CLOSED
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Posted by Larry B. 635 days and 10 hours ago.

Info Request

Imart, is the motor "surging" at full throttle? (r.p.m.s rise and fall quickly) What horse power motor do you have?Larry B.39621.5076560532

Accepted Answer

Imart, This sounds like an ignition problem to me. The stator generates ac voltage and it is rectified and becomes dc voltage that is stored in a capacitor in the switch box, a voltage signal from the trigger(also under the flywheel) triggers a switch in the box to release the voltage from the capacitor thru the primary coil wire at the proper time to cause the coil to fire the spark plug. The trigger and charge coils can become open or shorted causing a missfire. This will show up more on the top end of throttle range because the demand is greater. Or the ignition coil can be leaking spark or just not be holding up to the increased demand. If you need more info, just ask me I will respond.

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Expert: Larry B.
Pos. Feedback: 100.0 %
Accepts: 532
Answered: 6/22/2008

Marine Mechanic

Mercury/ Mercruiser Certified/Verado/DTS Yamaha Two and Fourstroke Certified 26 years experience

635 days and 9 hours ago.

Reply

so u think repacing the ignition might fix the problem

Posted by Larry B. 635 days and 9 hours ago.

Info Request

First you would have to see what component is bad instead of replacing all the parts. This done using a voltmeter with a peakreading attachment. Then you can pinpoint the problem. The only other thing I would suggest is hooking up a 6 gallon fuel tank and hose to the motor to eliminate the boat tank and your fuel hose and run the boat, if the problem goes away then it was the fuel system in the boat. if not then have someone troubleshoot the ignition system for you. Try Changing Spark plugs too.Larry B.39621.534981713

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