Motor missing at WOT

Bosunsmate

Admiral
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Apr 7, 2012
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6,129
No still don't agree. That high voltage pulse in the spark plug wire is there, no matter if the plug is wet or not. If it is WET with gas, it may not make a spark, but that HV pulse that triggers the light still occurred.


If theres no spark, im not sure the HV pulse would be there, itd just be like a battery with some cables but them not touching ground, no electrons flowing.
I will test this out another time i have my boat near my shed
 

wili

Seaman Apprentice
Joined
Apr 5, 2002
Messages
35
Ok, finally got out of the deep freeze here in Indy. Started checking for fuel problems. Changed fuel hose, squeeze bulb and all fittings from tank to motor. Checked tank dip tube and screen, tube was loose so I reseated it in the fitting. Inspected VRO fuel pump and diaphragms all look good. I took it out and still had the same symptoms but this time I hit the choke constantly and the miss went away but did not get to full RPM's. So I pulled the carbs and cleaned, reinstalled. Took out for another test and the miss is gone but will only go to 4200 RPM when I used to get 5200 at WOT. Do you think I need to pull carbs and clean again?
 

wili

Seaman Apprentice
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Apr 5, 2002
Messages
35
Should i do the drop test at wot or idle? I did it at idle and didnt notice a change. I did perform a high speed shutdown and the middle cyl plug was oily with other two dry and gray on the tip. I replaced plugs and did another high speed shutdown and this time the middle plug looked brand new ( nice and bright). The other two were the same as before. What could this indicate?
 

Bosunsmate

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Apr 7, 2012
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Should i do the drop test at wot or idle? I did it at idle and didnt notice a change. I did perform a high speed shutdown and the middle cyl plug was oily with other two dry and gray on the tip. I replaced plugs and did another high speed shutdown and this time the middle plug looked brand new ( nice and bright). The other two were the same as before. What could this indicate?


Hook a timing light up, it might be intermittent firing.
Sounds like id concentrate on that cylinder. You could swap a carb on to that cylinder and see if what you notice stayed with that cylinder or moved with the carb
 

wili

Seaman Apprentice
Joined
Apr 5, 2002
Messages
35
I took the boat out and did a full throttle drop test by pulling spark plug wires. Found middle cyl not firing. Swopped ignition coil with top and middle cyl. Middle cyl continued to not fire. Swapped spark plug wire with top cyl. Middle cyl still not firing. I did check the middle carb to ensure the float was filling the bowl by taking the plug out and pumping the squeeze bulb. Where do I go from here?
 

Boat Doctor1

Petty Officer 2nd Class
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Sep 29, 2012
Messages
123
1st thing id do is check the spark plugs?? then plug wires for arcing @ night -run @ night & have someone look!
 

Bosunsmate

Admiral
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Apr 7, 2012
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6,129
Put your hand over the carb, are you getting suction into it or is it blowing back indicating reeds are stuffed?
Check with a timing light, see if its firing and therefore its not getting fuel or its firing out of time
 

racerone

Supreme Mariner
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Dec 28, 2013
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What are the results of a compression test.--------Motor should be running at about 5500 RPM so something is wrong here.
 

Fed

Commander
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Apr 1, 2010
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After everything you've said I'd re-visit the middle carby.
 

boobie

Supreme Mariner
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Nov 5, 2009
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There may be something in the high speed jet in the middle carb.
 

wili

Seaman Apprentice
Joined
Apr 5, 2002
Messages
35
I took the boat back out and checked all cylinders with a timing light. All cylinders are firing, no miss on any cylinder. I believe the miss went away after I cleaned the carbs the second time, this is when it started running better just no power to get above 4200 rpm. I checked the DVA readings going to all ignition coils on the orange wires. All three readings were 230V. I checked fuel coming into the throat of the carbs, the middle seemed to be a little less than the other two but it is hard to tell, not that much difference. Last test was to cover the throat on the carbs, top cyl dropped rpms a lot, middle cyl dropped a little but when I released my hand the motor took off for a second or two, the bottom cyl dropped rpm a lot not the same as top cyl but more than middle cyl.

The reason I havnt swapped the carbs is because I read somewhere to not mix the carbs because they may be jetted or setup differnt for each cyl. Is this not true? I just do not want to cause damage to the powerhead.
 

racerone

Supreme Mariner
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Dec 28, 2013
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When was the compression test done ?----Obviously something wrong with cylinder # 2 ----reed valves / carburetor / cylinder compression.---Should not be hard to figure out.
 

pn

Petty Officer 1st Class
Joined
Apr 20, 2013
Messages
374
this may be off subject but when you prime your bulb does it stay hard for a couple minutes, or does it leak thru your VRO diaphram, down into your pulse line, down into your crankcase...down into low rpms.
 
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