What can I do to make the motor run without hesitation?

Question

Thanks! I am the one working on the 70 hp Evinrude...The battery charged resulted in a started motor...Once it got started, I remembered why I stopped taking it out...The motor bogs down when the throttle is engaged and full engaging only bogs it down until it quits running.

I think I know why - It is the Choke Solenoid...I do not have the grooved piston that actuates the choke via spring. Wher can I get one or how do I by-pass it? Can I rig a manual choke (Like a lawn mower) to adjust as I accelerate?

Answer 1

1976 model, right?

One of the most reliable outboard motors ever made.  I have a '79, virtually the same design, runs as good if not better than the day it was made.

The choke is for cold starts only, and there is a manual on/off lever, sticks out behind the starboard side of the airbox cover.  

Myself, I have very little patience for something like an electric choke that's not working -- that plunger can't be that expensive, surely.

But don't choke it while it runs -- anyway with 3 carbs you'll have a heck of a time figuring out which ones are running lean.

If choking the motor will make it run right, then there's a couple things you need to know:

1.  you've got a cylinder or two starving for fuel due to gummed carbs.

2.  starving for fuel means no lubrication in those cylinders.

3.  the carbs need rebuilding.

There's a couple things to check before tearing into the carbs.  

Compression test.  No point spending time & money on a motor with bad compression.  Look for all 3 to be within 7% or so of each other, and anything upwards of 100 PSI would be ok.  I'd expect 115 to 120 on a motor of that vintage.

Next, spark test.  Not a *spark plug* test.  Spark should jump a 7/16" gap on an inline tester outside the cylinder.

Fails the spark test, post a question about how to troubleshoot the ignition.

Then you want to check on your carb/spark timing synchronization:

The timer base needs to move smoothly all the way to it's stop without sticking.  The timer base is linked at the top of the throttle lever (starboard side of the engine), just under the edge of the flywheel.  This is what advances the spark timing.

The carb throttle butterfly valves are closed at idle, stay parallel, and end up horizontal at WOT.

Also make sure the choke butterflies stay open except when the choke is engaged.

The throttle cam needs to hit the cam follower roller right on the mark when the throttle lever is advanced.  Starboard side of the engine, the cam is a flat semi-triangular metal piece that pivots forward and down when you advance the throttle;  the leading edge is curved, and contacts a roller on the middle carb linkage.

If the carb butterflies start to open before the spark is advanced, the engine will just die out when you try to accelerate.

If all of the above check out, then order 3 carb kits and get started.

These carbs are remarkably simple devices, with 3 fixed jets apiece, nothing to adjust except the float height.  Instructions will be in the kit, run into any problems, just ask.

take 'em apart, soak 'em overnight in B-12, spray through all the orfices with compressed air (or aerosol carb cleaner), reassemble with the new kits, put 'em back on that's it.

Answer 2

You only need a choke to start it, not to run on..If you're starving for fuel while running you have either leaky fuel lines/connections,plugged fuel filter or bad fuel pump. A good test: If you have a primer bulb on the fuel line try pumping it while it is "bogging down". You can also pump it up and look for leaks.