Problems with a J25 2001 3 cyl.

[daselbee]

J25TEL3SIE. This is a three cyl 2001 Johnson looper with optical ignition.

First, compressions are: 1---90, 2---95, 3---80.
Does anyone know if this engine should have higher compression than this? It sure seems to turn over by hand way, way to easy.
I cannot feel any resistance as a piston comes up in the cyl...it just seems as if the plugs are out it is so easy to turn.

Second, I am having a fit with the ignition. The sensor under the flywheel is clean, the encoder ring is not broken, but I cannot retard the timing back down to 4 degrees ATDC (spec) for idle. It will not idle, slows down way to slow, and dies.
So, trying to do a link and sync is almost impossible...it only runs when timing is at about 6deg BTDC. Ten degree difference.

My question...can a bad sensor still provide good strong spark, but just way off...like ten degrees?

Carbs are spotless. Owner has a spare pack we will try tomorrow.

But this timing being way out......weird. Anyone with J25 3 cyl experience?

 

[hidef]

Re: Problems with a J25 2001 3 cyl.

The engine has Quikstart and it needs to be disabled before you can set the timing. I don't have my manual with me this is from a post of mine to another member.

At idle the timing should be 4 degrees ATDC and at full throttle it should be 20 degrees +or- 1 degree BTDC. You really need to get a service manual if you have to set the timing. When checking or setting the idle timing make sure the QuikStart is disabled by disconnecting the temperature switch black and white lead connector (located between cylinder 1 and 2 on head) and use a jumper to connect the black and white wire to clean ground. Wait about ten seconds for QuikStart to return the timing to normal. Make sure the throttle arm is against the stop. The engine timing pointer should align with the correct degree mark of the flywheel. The boat has to be in the water and moving to accurately check the timing.

If the engine you are working on still has the OMS system get rid of it. The check valves in it are prone to failure. The oil tank will fill with gasoline eventually causing a lean condition.

 

[boobie]

Re: Problems with a J25 2001 3 cyl.

As said above if the mtr still has the OMS system on it, get rid of it and start mixing your fuel 50:1. Other wise you may be looking at a blown mtr.

 

[daselbee]

Re: Problems with a J25 2001 3 cyl.

Thanks guys. Yes, I have a factory manual. I was starting the engine, and waiting for QS to drop out, then looking at timing. But, this thing is so erratic, maybe I have not actually had QS to drop out.
I will disable it by the white/black wire tomorrow and re-check timing.

As I slowly retard the timing with the idle stop screw, I get to 6BTDC which is where it runs the best...maybe 900 rpms. I know this is incorrect. As I retard more, toward the 4ATDC goal, engine runs slower and slower, and then cannot run anymore and quits. No lean sneeze...just stops.

I was wondering if this was designed as a much higher compression engine...like 120 or so.....anyone have real measured compression numbers?

I just cannot think of why or how the timing just will not adjust to the spec'ed goal of 4ATDC. Book says to turn the carb idle mix screws out to 0.39" length from the carb body. NOT "X" turns out, etc, but measure the gap between the head of the screw and the body of the carb...crap...what will they come up with next? But I have done so on all three carbs, and I have also tried different turns both in and out of the idle screw...it just will not idle that slow. Butterflies are absolutely closed, and the idle circuits are spotless. No clogs anywhere.

I wonder why I can never get an engine in here that is a simple fix? You know, an obvoius issue, and fixed right up....I always get the problem children....

Anyway, compressions? Just so I can compare....

Thanks...

 

[hidef]

Re: Problems with a J25 2001 3 cyl.

Sorry I don't have compression numbers for you I have never checked mine. I know my engine idles at about 850 or so in neutral but in gear it is just over 600. I have never mucked with my timing other than to check it. You do have to ground out the wire it is the only way to make sure the Quikstart behaves itself. Even after grounding it out it takes 10 seconds or so for it deactivate.

Have you checked to make sure the timing pointer hasn't been moved? If some one played with it that could be giving you headaches too.

 

[daselbee]

Re: Problems with a J25 2001 3 cyl.

Yes, timing pointer is dead accurate. I checked it with a piston stop tool.

OK...plan is....disable QS and re-check timing. Double check temp sensor.

Thanks again.