Boating Discussion Thread, Spark Question in Boats; I have a '92 Yamaha 50hp 2-stroke outboard with a weak spark on the third cylinder. The spark plug is ...  | | 
Feb-03-2008, 12:58 AM
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#1 | | Registered User
Name: Al Vessel: 18.5', Gregor CC Location: SGV Job:Fish Whisperer
Posts: 301
| Spark Question
I have a '92 Yamaha 50hp 2-stroke outboard with a weak spark on the third cylinder. The spark plug is not wet and it does not seem like its burning any fuel in that cylinder. The compression on that cylinder is reading about 110PSI and the other two cylinders at 120 PSI. I changed the spark plug with two new plugs and no change.
What may be causing a weak spark on the third cylinder?
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Feb-03-2008, 01:23 AM
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#2 | | TEAM EPIC FAIL
Name: Jason Age: 24 Vessel: 27, Seaway, Yank n Crank Location: Yorba Linda (Sucks), Ca Job:Logistics Bio: Love to fish, hunt and ride dirt bikes..
Posts: 2,673
| Quote:
Originally Posted by SeaHawk IV  I have a '92 Yamaha 50hp 2-stroke outboard with a weak spark on the third cylinder. The spark plug is not wet and it does not seem like its burning any fuel in that cylinder. The compression on that cylinder is reading about 110PSI and the other two cylinders at 120 PSI. I changed the spark plug with two new plugs and no change.
What may be causing a weak spark on the third cylinder? | Could be as simple as a bad plug wire...
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Feb-03-2008, 06:44 AM
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#3 | | Captain
Name: Gary Age: 62 Vessel: 28' Aquasport "Reel Adventure II" Location: Poway Ca Job:Mobility Vehicles & Modifications, W/C Lifts , Repairs etc
Posts: 1,801
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bad plug wire , bad coil.....
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Feb-03-2008, 12:41 PM
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#4 | | Registered User
Name: Al Vessel: 18.5', Gregor CC Location: SGV Job:Fish Whisperer
Posts: 301
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I'll check the plug wire and coil.
Thanks
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Feb-03-2008, 04:08 PM
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#5 | | Registered User
Name: Al Vessel: 18.5', Gregor CC Location: SGV Job:Fish Whisperer
Posts: 301
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I replaced the coil and plug and nothing has changed.
Any other possibilities?
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Feb-03-2008, 04:38 PM
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#6 | | Registered User
Name: kedd Age: 43 Vessel: 23' center console Location: CT Job:Marina Mgr.
Posts: 7
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How do you know it's a weak spark?
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Feb-04-2008, 03:49 PM
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#7 | | BORN TO FISH NOT CATCH
Name: RICH-E-RICH Age: 32 Vessel: 22' GRADY WHITE JUST-IN-TIME Location: SF BAY AREA Job:CERTIFIED MARINE TECHNICIAN Bio: I LOVE TO FISH AND WORK ON BOATS!! SEE U GUYS ON THE WATER
Posts: 503
| sparky
u need a meter and a dva
check the grounds also
__________________  HUMAN BUILT = HUMAN FIXED | |
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Feb-04-2008, 04:29 PM
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#8 | | Captain
Name: Art Age: 39 Vessel: 40' Luhrs Convertible, Luhr'd Away Location: San Pedro/ Victorville Job:Elevator Service/Repair
Posts: 2,888
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Bad mag? I'm in the same boat as you, just a different issue
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Feb-04-2008, 04:33 PM
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#9 | | Village idiot
Name: Steve Vessel: 17' Invader, Bottom Line & crew on 26' Blackman - Zarco Location: Santee, Bahia de Los Angeles Job:Yes, still at it
Posts: 3,054
| Quote:
Originally Posted by Luhr'd Away Bad mag? I'm in the same boat as you, just a different issue | Pretty sure those engines use a CDI ignition, so no mag...
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Feb-04-2008, 04:49 PM
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#10 | | Registered User
Name: RICK Age: 48 Vessel: 22' Shamrock Predator "MATTANZA" & Boston Whaler 25' Outrage "MATTANZA II" Location: TIERRASANTA Job:Mortgage biz. I sell money... want some?
Posts: 1,179
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Bad wire, maybe charge coil. Try swapping the ????? bad wire with a known good wire. If the problem goes away, then you know it's the wire.
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Feb-04-2008, 06:02 PM
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#11 | | Registered User
Name: Al Vessel: 18.5', Gregor CC Location: SGV Job:Fish Whisperer
Posts: 301
| Quote:
Originally Posted by kedd How do you know it's a weak spark? |
When I pull each spark plug cap off with the motor running, I can see, hear and feel the difference in each plug.
Any additional thoughts?
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Feb-04-2008, 06:03 PM
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#12 | | Registered User
Name: Al Vessel: 18.5', Gregor CC Location: SGV Job:Fish Whisperer
Posts: 301
| Quote:
Originally Posted by Bottom Line Pretty sure those engines use a CDI ignition, so no mag... | Your right, it has a CDI Ignition.
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