Rough Idle?

M

maldoro

Seaman
Joined
Jul 24, 2002
Messages
57
Hi all, I have a 2006 Johnson 115. My motor sound like it is running on 3 Cylinders. Here is what I've done so far.

Rebuilt Carbs with new kits - I've been through them 3 times.
Checked spark - Strong makes the 7/16 jump with no issues. Also verified with inductive timing light.
Replaced Intake manifold gaskets - Motor would stall before this was completed, gaskets were bad. Replaced Fuel lines and inline filter. Drained tank and replaced with fresh gas.
Decarb motor using BRP engine tune.
Replaced Ignition switch
Verified Primer solinoid is functioning properly.
Compression is between 125 -130 on all cylinders

When I pull the #4 wire, there is no change in motor. When I pull #3, very slight change, #2 is noticible and #1 kills motor. I swapped coil packs and wires no change.

The boat runs very good at WOT, just idles crappy. My Mechanic is coming back out on Wednesday, he mentioned he is going to swap out the OIS sensor. Sorry this post is so long, but I wanted to provide as much information as possible. Any other thoughts?
 
C

chubcobear

Seaman Apprentice
Joined
Apr 21, 2009
Messages
41
Re: Rough Idle?

Is it possible that the plug wire of #4 is grounding on the upper latch bolt of the engine cover? A crack in the plug insulation can permit this. This was a sometime problem with earlier model crossflow V4 engines. It happened to me.
New plug wire (without cracked insulation) solved the problem. It began running on all four cylinders again.
 
B

BCorn

Cadet
Joined
May 26, 2009
Messages
19
Re: Rough Idle?

i have similar problems,.......it is in shop having new reed plate gaskets installed...we shall see this weekend if that fixes the problem.
 
M

maldoro

Seaman
Joined
Jul 24, 2002
Messages
57
Re: Rough Idle?

BCorn said:
i have similar problems,.......it is in shop having new reed plate gaskets installed...we shall see this weekend if that fixes the problem.
Click to expand...

My manifold gaskets were wasted. I thought for sure that was my issue. I know it was part of the problem because it wouldn't stay running. Now at least it running but running rough. I'm starting to think it's something with the optical ignition system. We shall see.
 
M

maldoro

Seaman
Joined
Jul 24, 2002
Messages
57
Re: Rough Idle?

chubcobear said:
Is it possible that the plug wire of #4 is grounding on the upper latch bolt of the engine cover? A crack in the plug insulation can permit this. This was a sometime problem with earlier model crossflow V4 engines. It happened to me.
New plug wire (without cracked insulation) solved the problem. It began running on all four cylinders again.
Click to expand...


I've been running without the cover (not in the water of course). I also swapped my plug wires around. I had a 1995 Rude several years ago and never had any issues until the motor was older then 5 years old. I've had this boat for 2.5 years and bought new. I'm really stumped as to what is going on.
 
C

cdoliver

Petty Officer 1st Class
Joined
Mar 18, 2008
Messages
211
Re: Rough Idle?

Well if you have compression and spark, it must be fuel related. How does the plug look? Wet or dry? Have you sprayed premix down the carb throat that services that cylinder to see if it picks up?
 
LubeDude

LubeDude

Admiral
Joined
Oct 8, 2003
Messages
6,945
Re: Rough Idle?

It could very likely be a linc and sync problem! Even if you checked it, it could still be off! Make sure your carbs are completely closed at Idle!
 
M

maldoro

Seaman
Joined
Jul 24, 2002
Messages
57
Re: Rough Idle?

plugs are wet. I sprayed fuel into the carb and it choked it out. Didn't pick up. My mechanic is coming over in the morning. He thinks the lower crank seal may be leaking. I have this thick goop coming out of the prop, so he might be right..not sure. That will be the last resort. He is going to double check the timing and he has a spare powerpack, OIS sensor and fuel pump that we can try. We may be pulling the powerhead. I will post our results.
 
M

maldoro

Seaman
Joined
Jul 24, 2002
Messages
57
Rough Idle Solved

Rough Idle Solved

We traced it back to a bad fuel pump. I have issues in the past on other motors with the VRO. I know they are much better now, but I decided to go with kit #438402 which is the factory fuel pump without oil. I'm already adding ethenol treatment so adding oil is not a big deal plus I have piece of mind that my motor is properly lubricated. I plan on rebuilding the bad pump for future use. Thanks all for your help with this and recommending the factory manual. I received the manual yesterday and today the boat is ready to go.
 
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