'77 Johnson 115 starved for fuel

[polvaultr]

So last week I rebuilt the carbs because of a sticking float that was flooding the engine. Now, in the water, she is starved for fuel. If I hold in the ignition choke, with the warm-up lever engaged, she will fire up, rev up to around 4k rpm, then bog down and die. If I hold in the choke, I may get a few extra seconds of run time. I'm thinking now it may be one of a few things:

1: fuel pump
2: fuel line
3: something else I have no clue that hopefully someone can point me in the right direction to

It really confuses me because on the trailer w/ muffs on, she runs great, idling about 1k, and revving w/ warm-up to about 2k. I've had her running for as long as 20 min on trailer. I understand the extra strain on the motor cause by the pressure of the water, just kinda boggled at this point.

Thanks for any and all input!

Edit: forgot to mention that I just put ethanol treatment & stabilizer in the tank. Could that have anything to do with it? Just got it running on the trailer again after about 5 min of fighting with it. Now it will flood with ignition choke in...

 

[emdsapmgr]

Re: '77 Johnson 115 starved for fuel

Check your spark on each plugwire when the engine is warmed up to normal operating temps. That engine will seem to run just fine on the trailer on only 2 or 3 cyls. It needs all 4 firing when the prop is buried under 20" of water.

 

[polvaultr]

Re: '77 Johnson 115 starved for fuel

Checked plugs prior to launching when I was doing diagnostics on poor running period. All plugs gave good spark. After getting dad's input, also thinking maybe fuel filter as well. Looking around online (including iboats forums, it appears as they are just plastic screens that can be cleaned and replaced. Any thoughts on that, or should I just pay the $4.85 to replace it if it looks cruddy?

 

[emdsapmgr]

Re: '77 Johnson 115 starved for fuel

When the engine starts to bog, you can do a fuel test. Start priming the fuel hose bulb-constantly. This will force extra fuel around the pump, directly into the carb bowls. If the engine runs normally as long as you constantly prime the bulb, you have a fuel delivery problem.

 

[polvaultr]

Re: '77 Johnson 115 starved for fuel

Not a bad idea. Will need to have a 2nd person to turn key while I prime bulb. If that does solve the problem, I'm assuming replace the pump? I'm going to tear it apart to check the filter tomorrow since I have time. I have checked and the bulb stays firm the entire time, so I'm guessing it isn't a tank-to-pump issue.

 

[Bob_VT]

Re: '77 Johnson 115 starved for fuel

Are you sure the fuel lines are not cracked and sucking air? All the floats are correct? If you are not positive I would recheck everything. I have allot of experience with doing v-4 carbs and I know I am capable of missing things.

I would also check the spark and all the wires again too.

Trust me ..... we have all made tiny errors that drove us nuts and they were actually simple fixes.