Logo
FULL SITE MENU

Mercury 50 2-stroke 1989 ignition problem continues after component renewal

D

DIY

New member
My mercury had relatively old electrical system components. On the end it burned the Power pack.

I replaced ignition high voltage cables to spark plugs, all coils, stator and the power pack. In addition I maintained all earthing points of the ignition system and wire connections. The flywheel magnets are visually very fine.

After few hours of driving it burned the power pack again. I was able to drive to my harbour at idle. Thus, I replaced the recitifier and ignition timing ring. Of course I renewed the power pack, again. The remote control unit of this outboard is almost new.

At revolution higher than about 1500 RPM the engine runs very smoothly. The engine is both powerfull and accelerating well. Normal cruising speed is nice to drive and high, nominal RPMs can be reched well.

However at idle the engine has clear and relatively strong misfiring. It might be on multiple cylinders as the misfiring shakes the engine. Almost as if the earthing point that earthes all wires from coils would be loosen - it is not loosen because I maintained it well. Faulty set up of the timing is not the cause, I checked.

Due to misfiring at idle I have the feeling that although massive renewal of components, the root cause of the failing power pack is still not found and fixed. Could the forum readers help me furhter with this mysteriously hidden root cause. What should I try next?
 
If the "power pack" is burned out it won't run at all you'll have no spark, have you set the low speed needles to approximately 1 1/4 turns out in F gear while underway?
1,500 rpm is the transition point when the motor starts to run on the hi-speed circuit so the low speed doesn't affect it.
 
Test ignition maximum output.-----Does spark jump a gap of at least 1 cm on all leads ?---Water pump impeller replaced?----Post compression test results as well.
 
faztbullet said:
Describe symptom of burnt pack
Click to expand...

When the power pack burned last time, the symptoms were:
at first at cruising speed few strong misfirings. Then the power was lost and the engine revolutions went down to almost idle.
It did not respond to throttle opening anymore, and too much throttle opening was bad as the engine was not able to burn the ecess fuel.
The engine barely run at idle, and the ignition system did not give higher revolutions. Thus I placed the throttle almost to position idle.
By doing this I was able to curuise at idle the remaining 7 miles to my harbour. The ignition had many interruptions during the last mileages, but did not stop.

After replacing additional components as described in my previous post, I can drive again, but I'm wondering due to misfiring at idle weather the root cause for burning power pack was truly found. I would rather not burn the power pack again....
 
What brand of powerpack (Switchbox) did you install? Quicksilver, Sierra, CDI are trustworthy...and cost a couple $100. I noticed that on ebay and Amazon, other brands (Chinese knock-off?) sell for $30-$40 and I suspect these may not perform as well.
Also, have you checked all the grounds on the powerhead and switchbox?
 
Back
Top