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3.8 Running Rough

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Chris Lucas
New member
Username: dyaustech

Post Number: 1
Registered: 04-2008
Posted on Friday, April 25, 2008 - 05:33 pm:   Edit Post Delete Post View Post/Check IP

During the end of last season, my port motor started to mis fire.. ran rough.. and eventually wouldnt get above 3000 RPM or so.

I changed the Points, Condenser, Rotor, Cap, Plugs, Oil & Filter... Still same issue. I checked for a vaccume leak and I dont think I have one. I am pretty darn sure its not a fuel issue, I am leaning towards electrical or timing.. somewhere like that.

The boat starts okay. Idles a little rough.. you can hear it miss... see it on the tach too.. its not steady like it used to be.

Ideas would be much appreciated. This is my first boat. Been on Submarines a long time.. know how to fix damn near anything on one of those but come to my own boat and I feel like a darn fool. LOL
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Bob Hill
Advanced Member
Username: boatin_bob

Post Number: 542
Registered: 07-2006


Posted on Friday, April 25, 2008 - 06:01 pm:   Edit Post Delete Post View Post/Check IP

Probably want to do a compression test but one of the primitive type tests I do is using a pair of plug wire pliers pull them off one at a time while idling and listen for a drop in RPM's as well as listening for the spark jumping to the plug.
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Chris Lucas
New member
Username: dyaustech

Post Number: 2
Registered: 04-2008
Posted on Friday, April 25, 2008 - 06:28 pm:   Edit Post Delete Post View Post/Check IP

Bob, thanks for the info. I just found the + terminal on the coil was a little loose so I tightened it. Now it starts even better.. seems to idle just fine.. but when I push up to around 3000 rpm it bogs down. I am suspecting a timing issue now, since I replaced the Points. I am going to check that here in a few. Will keep you posted. Thanks!
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Chris Lucas
New member
Username: dyaustech

Post Number: 3
Registered: 04-2008
Posted on Friday, April 25, 2008 - 08:42 pm:   Edit Post Delete Post View Post/Check IP

So lessons learned on this one. When I changed the points I neglected to attach the spring, only the condenser was attached.. so at low RPM it ran fine, but once you revved it up, the condenser spring didnt have enough "ummph" to close the gap quick enough, thus causing the timeing to go out of whack, causing stumble. Phew. So now everything is back in order, both engines running like a champ! Will test waterborn tomorrow. :-) :-)

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