Is a Float Height Gauge needed?

[BassFish]

1989 Johnson GT 150

I recently rebuilt the carburetors and set the float height level with the carb body. The float drop was set at 1" which is the middle of the specification.

The engine is still smoking like it is on fire. I am running it on a remote tank with a known ratio of 50:1. I checked the primer solenoid/enrichner to see if it was leaking. I also checked the VRO pulse fitting by pulling 15 in/Hg vacuum and it did not leak. How can this engine be running so rich? Do I really need the OMC gauge to set the correct float height? It seems like that is the only thing that it could be.

Thanks

 

[jonesg]

Re: Is a Float Height Gauge needed?

Well oil smokes, gas doesn't.
So wheres it coming from?

You have good spark?

Have you tested it?
Is the VRO disconnected?

Float is set with bowl upside down, level with mounting flange.
You didn't say HOW you set it.

Do you have the factory service book?
www.outboardbooks.com

 

[jtexas]

Re: Is a Float Height Gauge needed?

From your description, sounds like you're running 50:1 premix gasoline along with the VRO pump, which is double-oiling the motor.

But you sound surprised about the smoke, so I'll assume the oil pump side of the VRO is disconnected.

You also didn't mention any symptoms other than excessive smoke. Cold start, warm start, idle, acceleration, low-speed, hi-speed operation all ok?

I'll also assume you're experienced enough with 2-strokes to know what constitutes "excessive".

Go over to the "Engine FAQ" section of iboats, to the second page, and read the thread on "Decarbing your motor". That should help.

If I misunderstood your original post, and it's *not* premix, note that if the fuel line is sucking air, the VRO will dump more oil into the mix because of the increased volume of the aerated gasoline.

 

[BassFish]

Re: Is a Float Height Gauge needed?

Sorry for the confusion the oil line going to the VRO has been disconnected. And the engine is definitely smoking excessively. I was trying to verify that the float height was set correctly by making it level with mounting flange and not some weird height based on the gauge recommended by the service manual. The problem other than excessive smoke is that when you have it in a test tank and put it in gear it will cut off 50% of the time. It is hard to set the idle speed in gear when it keeps cutting off. The idle speed in neutral seems way too high at 900 - 1000 rpms. Could weak spark be causing all of this? All cylinders have spark on a Stevens spark board.

Thanks for your replys

 

[jtexas]

Re: Is a Float Height Gauge needed?

yup, figured you knew what you're talkin bout. I've never needed the float gauge, eyeballing it has always worked for me. Any chance you might've forgot the o-ring under the valve seat?

Do those carbs have adjustable slow speed jets?

Couple ways to tell if the float valve isn't fully closing: if you can blow air into the gas inlet with the carb held upside down, and the if you can force gas out the carb throats with the primer bulb. Sometimes those methods work, but sometimes they test satisfactory in spite of the valve is leaking anyway.

Sounds like it's not hitting on all cylinders; esp. when you shift into forward.

If your spark tester is set for at least 7/16", then spark's good. What's the compression?

Are all the plugs showing a rich mixture?

Could the shift interrupt switch be sticking?

The decarb procedure is all I got left.

 

[BassFish]

Re: Is a Float Height Gauge needed?

After checking spark for the 3rd time with a spark board I noticed that #6 missed sometimes. This was not even noticeable with the timing light or the spark board the first 2 times. To determine whether it was the power pack or ignition coil I switched the primary leads #6 to #4. The miss moved to #4 indicating power pack failure. Just to be sure I switched again with #2 but the miss stayed with #4. This was baffling until I positioned all the spark plug leads where they could not touch each other or the engine. Then I had good spark on all cylinders. This hit and miss excessive smoke problem now seems to be bad plug wires. Seem right to you??

Thanks for all the help. Decarb is on the list once the leads are replaced.

 

[Lion hunter]

Re: Is a Float Height Gauge needed?

It may be bad plug wires but I remember on early model trucks (only chevy 350's IIRC) that the plug wires would build resistance and not fire correctly if 2 wires in the firing order were to close to each other. So just seperating them may work. You can check for lost spark by going out at dark and running. If any wires are sparking to ground you should be able to see it.

 

[jonesg]

Re: Is a Float Height Gauge needed?

I'd say misfire due to weak wires.

 

[jtexas]

Re: Is a Float Height Gauge needed?

ignition misfire is contributing no doubt. I'd blame it for the intermittent idling problem for sure. Don't know how much smoke it generates. Let us know if that fixes it once & for all.

 

[seahorse5]

Re: Is a Float Height Gauge needed?

What are the idle temps of each cylinder head?

Different oils smoke much more than others. The Evinrude XD-50 oil is a synthetic blend and has hardly any smoke in a healthy running motor.

Are you sure the "50:1" premix is mixed correctly?

 

[tal]

Re: Is a Float Height Gauge needed?

I was chasing around a mis and hit idle on my 85 120. Turned out to be a series of things ranging from the foam under cowl breaking apart and being sucked into the idle jets to a bad plug wire and a malfunctioning thermostat. Sounds like you have a spark tester but you can also hookup a regular timing light and shine in a dark place to watch the spark on each cylinder. My miss followed the bad wire so I replaced it.

I still have an occasional spit out of my idle speed jets that I don't know what the cause is. I've set my floats in 4 different places and it makes no difference. I've checked for air leaks and such as well and can't find out why this happens. I'll be watching to see if you come up with a fix.

 

[BassFish]

Re: Is a Float Height Gauge needed?

Put the engine in the water today. Engine was running much better with the new plug wires but still smoking more than it should. Engine starts with no problem but only idles well when level. When trimmed in (down) the engine stalls. Trimmed out (up) it runs well. The only way to get the boat on plane is to start with the engine trimmed up and get the engine to 2500 to 3000 rpms which is not on plane but as you trim down the nose of the boat will drop and the boat will take off.

There are no problems once the boat is on plane. As soon as you slow down and the boat comes off plane the engine will stall if not trimmed up.

Float heights have been checked twice and are level with the mounting flange.

Could some sort of gasket leak cause this? I have noticed some black oil that may be coming from the base gasket. The only other thing that I can think of that can't be tested is a crack in the block. It just seems like for the engine to run so well at WOT the block has to be fine.

Any thoughts or suggestions are greatly appreciated!!

 

[jtexas]

Re: Is a Float Height Gauge needed?

the exhaust relief ports, two holes just below the powerhead on the aft end of the motor -- when the boat's in the water with the motor trimmed down, are they submerged? They need to be clear of the water at idle.

assume your spark problems are sorted out?
what about compression results?

You mentioned some kind of oil leak, can you pinpoint the source? should be a hose running from the air silencer to the crankcase or manifold, to recover the oil that collects in the airbox.

 

[BassFish]

Re: Is a Float Height Gauge needed?

I had no idea that the exhaust ports would make that much difference but I bet they can and I bet they were under water trimmed in.

Spark problem was fixed with new wires.

Compression is 95 psi on all 6. It would be nice to be over 100 but since they are so close and they are all exactly the same and the engine runs well at other angles and at WOT it should be okay.

The hose was connected to the air box but the leak appears to be coming from the base gasket near the front of the engine. Close to wear the shift shaft comes up and it is very difficult to see.

Thanks for the awesome tip!!