'94 Merc 9.9

[Backlash]

A friend brought over a 9.9 Merc with the following symptoms:<br />Starts right up....first pull.<br />Idles smoothly BUT occasionally "stutters" and when it does there's a click sound coming from the lower part of the powerhead.<br />When throttle is advanced beyond idle, the "stutter" increases and there is little power. At full throttle, the power does not increase (just the noise, a loud wooshing sound of air intake).<br />There is air coming out of the throat of the carburater (you can feel it) but no evidence of fuel spray coming out.<br />Compression is 100 psi in both cylinders. Strong crisp spark to both cylinders. Have pulled one plug wire at a time at all speeds and noted an equal loss of power with each. Pumping fuel bulb has no effect (bulb remains hard). Have de-carbed the engine, disassembled & cleaned the carb (to include fuel pump), checked the reeds (I thought this might be the problem but they appear to be OK), and there's no improvement. Have used two different fuel tanks, both with fresh fuel.<br />What am I missing? Help please.<br />Backlash

 

[FlyBoyMark]

Re: '94 Merc 9.9

Have you tried a different fuel hose? Also sounds like ignition breaking up under load. To verify fuel problem one way or the other, simply spray some fuel in carb while running to see if engine speed increases.

 

[Backlash]

Re: '94 Merc 9.9

Thanks for the response FlyBoyMark. I've tried two different tanks/hoses. Haven't sprayed any fuel mix directly into the carb.....will try it tonight. Any other ideas out there?<br />Backlash

 

[btwitche]

Re: '94 Merc 9.9

Hey Backlash. I have seen in the past a bad plug wire or connection cause the clicking sound you have mentioned. When a plug wire's insulation is damaged or there is any place where the output of the coil can arc to ground it will cause the engine to stutter since the plug will not fire. The arcing will also cause a loud clicking sound. Many times it will arc a couple of times and fire a couple of times- hit or miss at random. Try running the motor at night with the cover off and see if you see any arcing between the coil and the plugs... good luck

 

[Backlash]

Re: '94 Merc 9.9

Tried spraying fuel mix into the carb with no difference noted. Also ran at night with no evidence of arcing. Could a stator beginning to fail cause these symptoms? <br />Thanks for your help.<br />Backlash

 

[rickdb1boat]

Re: '94 Merc 9.9

Might have a broken reed valve. Pull the carb off and have a look. Also, use a length of small hose held to your ear(Stethoscope) to find the ticking noise.

 

[graddy]

Re: '94 Merc 9.9

You said that you inspected the reeds for cracks or chips. Did you inspect them for pre-load. Pre-load is a condition where the reed will be fully in tack but have a slight bend upwards in the middile. The tip of the reed would still be flat.

 

[Backlash]

Re: '94 Merc 9.9

Thanks for the quick responses Rick & DTS. I did check for pre-load on the reeds and they were completely flat against the reed block. What do you guys think about the stator starting to fail? <br />Backlash

 

[Backlash]

Re: '94 Merc 9.9

bump

 

[FlyBoyMark]

Re: '94 Merc 9.9

Ignition problem then under load...

 

[btwitche]

Re: '94 Merc 9.9

Hmm.. the clicking in unison with the misfires definitly says something. I have had the same symptoms with other engines and it was always traced to bad plug wires, or boots. Maybe the arcing is inside of the boot or within one of the power packs. The voltages within the stator are too low to cause any arcing or noise...Just guessing here. Good luck. Is the clicking frequency proportional to the engine speed?

 

[Backlash]

Re: '94 Merc 9.9

Hey B_B,<br />The clicking is proportional to the engine speed (in as much as it increases in frequency as the engine speed increases). However, it is erratic and unpredictable. <br />The reason I ask about the stator beginning to fail is the high speed winding tests a little on the low side (outside specs).<br />Thanks for your continued interest.<br />Backlash

 

[Paul Moir]

Re: '94 Merc 9.9

Bring a radio set to AM with you. If clicks come from the radio as well (set for a low band w/ no station) then you know it's arcing.

 

[rickdb1boat]

Re: '94 Merc 9.9

Paul, I gotta say, that's a great idea!!

 

[Backlash]

Re: '94 Merc 9.9

Thanks Paul,<br />I'll give it a try. Won't be able to try it 'till this weekend.<br />Backlash

 

[Backlash]

Re: '94 Merc 9.9

Thanks to all who responded earlier. Finally pulled the power head and found there's a pipe with a 1" ID that scavenges the exhaust from the powerhead through the midsection to the prop exhaust port. The pipe was nearly completely packed with carbon (maybe a 1/8" passage at the most). There was also a chunk of "hard as steel" carbon rattling around in the exhaust port of the powerhead. I suspect that piece caused the clicking sound. Removed the chunk, cleaned the pipe out, problem solved. Had me scratching my head but have since heard this is not uncommon with these small Mercs used primarily for low speed trolling. <br />Backlash

 

[AndyL]

Re: '94 Merc 9.9

Have you tried running it up in the dark.? May find the arcing easier. Certainly has all the makings of a tracking problem.