HALP! - 55hp Chrysler runs poorly until just before it's out of gas!

[Orator98]

I have a 1979 Chrysler 55 hp outboard on a 1984 Aero-Glas Phantom. The motor runs in neutral just fine. I've replaced both coils & plugs. Carb has been rebuilt. It purrs and runs great throughout the band when in neutral. When under power in either forward or reverse it runs horrible... won't plane out at all. It's going through 6 gals of fuel mixture (50:1) in about an hour. Then, just as it's running out of fuel it comes to life... runs like crazy... planes out instantly and then dies from lack of fuel.

I've read a bunch of the other articles on here but haven't seen anything quite like this one. I can only assume that it's something with the linkage. I'm a newb out outboards. I've rebuilt 4-stroke motors, worked on turbine engines, rebuilt all kinds of two-stroke motors... I'm baffled. I've had it to two different shops... got gouged pretty good by the first one whom swore it would be just fine. The second guy ran the motor with the lower in a horse trough. Neither one put the boat in the water and ran it under power.

In my inexperienced outboard mind, something in the linkage is causing it to run super rich.

Any thoughts?

Tom

 

[SkiDad]

sounds like your fuel pump is faulty to me or you have your float set wrong.

 

[Glastron_V210]

When the carb was rebuilt was it re-jetted? Float level reset??

Otherwise is the choke sticking on? Sometimes the solenoid gets sticky.

Other than that, what SkiDad posted.

Chay

 

[Orator98]

Thanks for the response. Supposedly both shops adjusted the floats in the carb. I don't know about re-jetting the carb. After charging me an arm & a leg to rebuild the carb I shared some rather harsh words and I'm not allowed back to the first shop. The second shop just adjusted the carb. I'm guessing that it's probably not the jets as the engine runs great... fantastic... awesome... when it's leaned out just before it runs out of fuel. I've talked with another shop about 40 miles away. He too thinks the fuel pump diaphragm is shot. So, I've got a potential drop-off appointment for the boat on Monday.

 

[oldboat1]

Is the choke flap opening? If partially closed, the motor will run rich with symptoms like your describe.
I think your diagnosis of rich running might be correct -- possible the h.s. jet was buggered up during cleaning.

As a carb empties, the mix leans out and the rpms increase -- it's what you listen for when setting the mix needle on motors with manual mix adjustments. If your fuel pump diaphragm has a hole in it or is torn (or tired -- lost it's flexibility and taken a set), you could get the stalling and the high revs (leaning out) before it quits.

Contaminated fuel (particularly water) can of course give you wonky operation. In addition, you might check the link and sync procedures discussed up at the top of the forum.

As a shop did the carb rebuild, my best guess is that you have a fuel issue. A shop runs on it's own known good gas. When you get home, you might run bad gas through the clean carb and end up with unexpected problems. It's most likely to happen with a permanent tank (old stored fuel, water).

 

[flyingscott]

revving it neutral means nothing but can cause engine damage.
Does the ball get hard when you pump it up
Was a link and sync done are both carbs opening at the same time
If it is flooding and running rich look behind the motor should be a bunch of unburned fuel in the water.
Go to the top of this forum in the sticky and find the link and sync topic from frank Acampora.
How did it run before you took it in.