running Rich and loading up

[JimboJames]

I have a 1973 70hp chrysler outboard. When I take the boat it runs great for 300 yards and starts to run rich and load up. I have cleaned out all three carbs, and they are clean. All the floats seem to work ok. The things I have done are new primer bulb and rebuilt the fuel pump. I am running NGK plugs maybe 3 weeks old with 2-3 hours on them. What is the needle setting on these carbs?

 

[jerryjerry05]

Re: running Rich and loading up

Out 1 and 1/8 turn.That's where you start.Then turn them in till it coughs/runs bad.Then out 1/2 turn.J

 

[john from md]

Re: running Rich and loading up

Try cleaning the fuel recirculation system. That system is identified by a couple of rubber hoses on the side of the engine and a vertical cover plate on the right side of the engine. You need to clean these out with spray carb cleaner. Also, you may have a elbow under the lower carb which is actually a small orifice. That always gets clogged from oil congealing.

When this system gets clogged, the engine loads up and runs rich.

John

 

[JimboJames]

Re: running Rich and loading up

I found the recirculation system on the side with an orifice in the middle. Should be able to blow threw that orifice? I can't seem to find anything under the lower carb.

 

[john from md]

Re: running Rich and loading up

If your engine had it, it would actually be behind the lower carb on the intake manifold. It would have a rubber hose going to it so, if you don't see it, your engine doesn't use it.

 

[JimboJames]

Re: running Rich and loading up

Ok I found it in the intake manifold. I am going to fire it up tomorrow. We will see what happens.

 

[john from md]

Re: running Rich and loading up

Your mixture screws should be somewhere between 1 and 11/4 turns out. Never go below 1 turn out as todays gasoline will burn too lean and burn a hole in your piston at WOT.

John

 

[JimboJames]

Re: running Rich and loading up

Ok had out on the lake yesterday and it ran pretty good, better than it did in the past. I did noticed that when I go WOT that would run the carbs out of gas. I know this because I made it die and it needed the choke start. It only acted this wat at WOT if I backed off a little it was ok.

 

[john from md]

Re: running Rich and loading up

I'm sure you know that your engine should not be leaning out and shutting off at high rpms. Did you notice if your bulb was soft when this happened?

The most common cause of this is sticking of the three check valves in the fuel pump housing. The check valves swell from the effects of alcohol in the fuel and start to stick. The fuel pressure is only about 1.5 pounds so it can't overcome the sticking and the engine starves.

If you remove the fuel pump housing, you can check these by slightly pushing on the poppet disk in the middle of the valve with a pencil or such. Additionally, the older valve poppets were colored amber or clear. The new material is black or grey and is made to resist the effects of the alcohol.