1978 Evinrude 75 bogs for awhile then takes off?

[Prince2e]

Hey everyone! I NEED SOME HELP! I’ve recently purchased a boat with a Evinrude 75 and i’ve been doing some maintenance on it. It was in pretty decent shape when I got it. Done a compression test- 120 on all cylinders. Did a spark test and found that the cylinder had a bad ignition coil so replaced that. Took apart the carbs- extremely clean and recently rebuilt with all the jets cleaned. Fuel pump and fuel lines have been replaced and checked for leaks and pressure. The issue i’m having is when I take off to go, the motor bogs down when trying to go full throttle. If I hold it there for awhile usually in about a minute it will finally accelerate and take off as normal. Can anyone give me a clue to what could be going on?

 

[iggyw1]

Sounds like you may be experiencing a lean fuel mixture problem. Adjust the slow speed needle valve about 1/8 to 1/4 turn to run a bit richer and see if that helps. Also, check any fuel filters that you have on the motor for plugging up &/or water in the fuel. Add a can of Seafoam to the tank and run the motor WOT for awhile to clean things out. Hope these suggestions help you out.

 

[Prince2e]

I did not know these carbs were adjustable. Where would this valve be and which direction to turn?

 

[iggyw1]

I did not know these carbs were adjustable. Where would this valve be and which direction to turn?

There may or may not be a slow idle needle valve on your carbs. I was making some suggestions in general on where to start on solving a lean fuel mixture problem, on what may be done to remedy a lean mixture. I am not a mechanic & I am really not familiar with your motor, but I was just suggesting what may be your problem, to try to help you out. If you do not have the needle valves on that motor, maybe someone will chime in that knows how to correct a lean fuel mixture without the needle valves. Could be that the carbs are not synced together.

You said you changed the fuel lines on your motor, did you replace the main line from the tank to the motor as well? I saw someone a few years back on this forum that had a problem with bogging down, and that was his problem. When he changed that main fuel line, problem was solved. Someone else on here changed his spark plug wires and that solved his bogging problems, but you said that you had a good spark, so the wires are probably o.k.

 

[F_R]

Check for a sticking timer base. If it lags, the carbs will open before spark advance occurs, and it will bog or even quit.