1999 Johnson 115 Poor Idle and Stalling

[Captain Jeff]

1999 Johnson 115 60 deg V4 J115PXEEM
Hi, I have never really been able to get a good idle on this engine. Last season I rebuilt all 4 carbs including new bowls and floats. Rebuilt the vapor separator and primer solenoid. Installed a new water separating fuel filter and primer bulb. Also a brand new VRO unit. I'm pretty confident I rebuilt the carbs well. This was probably the third time I rebuilt them and I am very careful during the process. Also cleaned the optical sensor and timing wheel and I checked spark on all 4 cylinders and had a good blue spark jumping the gap on the tester. I also checked compression and had around 115-120 on each cylinder. I also cleaned the oil tank and replaced the oil line and bulb last season. New spark plugs too.

I just did a link and sync today with the OMC ignition analyzer and there was a noticeable improvement in idle quality. It idles smoother but still not perfect. The main issue I have is that it stalls and seems to idle high (800-900 RPMs on earmuffs). It may seem to idle fine and then suddenly stall. It doesn't gradually die out as if it had a fuel restriction and it will restart instantly with a turn of the key.

Here is an example of what it does, you'll notice the idle starts out ok and then gets a little rough and stalls at the end. The engine is already warm and out of fast start in this video.
https://www.youtube.com/watch?v=qTfyr9tSQc0

Here is one time when it stalled and actually had a flame come out of the prop.
https://www.youtube.com/watch?v=8kAdhjxv5q4

The next thing I was going to try would be to adjust the idle screws on the throttle bodies. I thought it could be a lean sneeze but I'm not sure. I noticed the hex key idle screws seem to have a little play in them so maybe they vibrated lose. Does anyone know how many turns to adjust them? My Clymers manual doesn't have the setting. Any ideas of what else I can try? Thank you!

 

[Faztbullet]

Your wasting your time as that motor has to be in a barrel or the lake to do any adjustments .It has to have back pressure and get rid of the Clymer. Running with cowl off the sunlight can confuse the optical eye and that will cause idle and sudden stops.

 

[Bosunsmate]

Have you inspected your plugs? Might help narrow it down to a specific cylinder, if thats the problem

 

[Chris1956]

You did all that work with a clymer? I would recommend a OEM service manual.

The initial carb settings for a '98 Johnny 115HP 60*V4 is 5-3/4 turns open. I expect your motor to be the same.

Spark plugs are QL78YC?

 

[Captain Jeff]

You did all that work with a clymer? I would recommend a OEM service manual.

Yep, pretty impressive right? lol Some of the stuff in the Clymer doesn't even make sense or is wrong. I should have gotten an OEM manual a long time ago. Trying to order one today. Yes, I'm using the QL78YC plugs. Thanks Chris. They all look about the same so I can't really identify a problem cylinder.

Thanks for the info Faztbullet, I'll try a barrel today or getting to the lake.

 

[Captain Jeff]

Well I'm pretty much at my wit's end. So the boat is in the water now. I replaced the primer bulb because I was having issues holding a prime. It would lose prime if running at idle.

Now it will idle fine during the fast start, as soon as fast start ends it will only idle for 10-20 seconds before stalling. If I rev the engine in neutral it will stall. In both cases I can keep it running by pushing the key for the primer solenoid or by manually playing with the red primer lever on the engine.

These issues cropped up at the end of last season when the boat sat for a month before being winterized. Last spring I went through the whole fuel system as noted above and it ran good for the season. When I went to winterize I could barely keep the engine running long enough to fog it. When I got it running this year, it ran ok on earmuffs but not great. I did a link n sync and it ran better. Now that it is in the water it doesn't stay running. I fixed a leaky float valve in one of the lower carbs and checked the on engine fuel strainer and it was clean.

I know the fuel primer can keep the engine running but is it really a fuel issue or is dumping fuel in the engine just masking another issue?

I have the OEM Manual now but there are a million possibilities of where to start. It would take me weeks to go through every item. Any ideas on common issues or where I should start? Thank you.

 

[Captain Jeff]

I have some good news and bad news. The good news is that I fixed part of the problem. I checked the water separator and found one of the fittings slightly loose. I also removed the filter canister and found the gasket had swelled from the gas and was slightly larger than the canister groove. I was able to re-seat it and oil it up and tighten it on to the bracket. The engine runs better now and seems to run well above idle speed! The VRO must have been sucking in a little air and didn't have adequate fuel pressure.

The bad news... it still stalls at idle. It runs good during QuickStart but a couple seconds after the timing goes to normal, it stalls. The primer doesn't seem to help keep it running either. This is leading me to believe that it could be a timing/ignition issue. Bowls seem full of gas and I cleaned the air bleed orifices. I tried 1.5 turns on the idle screws but it would only run for a second. Went back out to 5 3/4 turns per manual and it runs fine in QuickStart.

Hopefully a clue: I checked the timing with a timing light at dusk during idle. During QuickStart the timing seems to be running at 4 deg. (before?) Top Dead Center. When the QuickStart deactivates, the timing goes to -6 degrees (I'm assuming the - means after top dead center?). Is this the correct timing for this engine? I did set the idle timing with the OMC ignition analyzer but I was using the Clymer manual at that point. I moved the tabs one notch aft and it changed to -5 degrees but still stalled. Any ideas? Thank you

 

[Chris1956]

Te OEM Service Manual cites 4* ATDC for the V4 idle timing. Sounds like you need 1 more degree. The next step is to adjust the spark/throttle pickup point.

 

[Bosunsmate]

I personally wouldnt think 1 deg will be causing much grief, a you trying cylinder drop tests?

 

[Captain Jeff]

Te OEM Service Manual cites 4* ATDC for the V4 idle timing. Sounds like you need 1 more degree. The next step is to adjust the spark/throttle pickup point.

Thanks Chris, I turned the idle jets out another 1/2 turn. Since I found the timing was 6* with the timing gun, I moved the idle tab two notches aft which brought the idle timing to exactly 4* ATDC. After these changes I started her up. It sneezed and stalled once or twice the first couple times I started it. After that it ran like a champ. I adjusted the throttle cable and timing lever tonight so the timing roller is touching the timing cam and the throttle cam is touching the throttle roller. They both move at the same time.

It idles in neutral and in gear (~850RPM) without stalling. Throttle response seems good. WOT is 5,600 RPM (14.8 x 17 prop on an 18' center console)

 

[Rustywrench]

Glad you have it for now. Next time you are out in the lake running stop & with the motor idling in gear trim up into the tilt range. Turn the engine full right (or left) and leave it that way. Be sure you have enough room to go around in circles. Run that way for several minutes. See if the idle gets rough or starts to sneeze & die? Keep up with which way you are turned.
Trim down & run the boat on plane.
Now do it again turned the other way. Remember it tales a while for the problem to show up. If you have a problem one way vs the other you have a recirculation valve blown open. They are found in the intake manifold. You can test them with a piece of small fuel hose. They should check in one direction & flow in the other. If they are blown open then they become intake leaks. Replace as needed. You can try flushing with brake clean. If they don't seat well, replace.
This test is good for 60* V-4/V-6 90hp thru 175hp.

 

[Captain Jeff]

Rustywrench, thats a great tip. I have always wondered about those recirculation valves but didn't want to tinker with them and create a new problem. That is a good non invasive way to test them. I'll try that out.