Help me adjust carbs on an 85hp Johnson

[pinchvalve]

I recently completed the restoration of a 1977 bowrider with a 1977 Johnson 85hp. When I hit the water, the boat starts and idles fine, and will run 50% throttle all day without issue. If I go WOT, it will run for a few seconds, then it slows dramatically. If I return to idle for a bit, it will go WOT again for a few seconds, but then fall flat after a few seconds. My theory is that the bowls are draining and not being filled fast enough for WOT.

I started by replacing the fuel pump and all fuel and vacuum lines. This helped a bit, I can run 60% throttle now. I added an electric fuel pump in place of the primer bulb, and with it pushing fuel to the on-board fuel pump, it will run 80% throttle, but WOT does the same thing. I feel like I am supplying plenty of fuel. (I have swapped fuel lines and primer bulbs as well with no change) I removed and rebuilt the carbs, so that's the area I think may be causing the issue.

The new floats were installed according to online videos, level with the bottom of the carb housing when hanging. This is an eyeball setting, not a millimeter-precise setting. Do I need to do more to adjust these perfectly? Is the float not allowing gas through the needle valve somehow at WOT? Is there a jet or other setting that I can adjust?

 

[F_R]

I recently completed the restoration of a 1977 bowrider with a 1977 Johnson 85hp. When I hit the water, the boat starts and idles fine, and will run 50% throttle all day without issue. If I go WOT, it will run for a few seconds, then it slows dramatically. If I return to idle for a bit, it will go WOT again for a few seconds, but then fall flat after a few seconds. My theory is that the bowls are draining and not being filled fast enough for WOT.

I started by replacing the fuel pump and all fuel and vacuum lines. This helped a bit, I can run 60% throttle now. I added an electric fuel pump in place of the primer bulb, and with it pushing fuel to the on-board fuel pump, it will run 80% throttle, but WOT does the same thing. I feel like I am supplying plenty of fuel. (I have swapped fuel lines and primer bulbs as well with no change) I removed and rebuilt the carbs, so that's the area I think may be causing the issue.

The new floats were installed according to online videos, level with the bottom of the carb housing when hanging. This is an eyeball setting, not a millimeter-precise setting. Do I need to do more to adjust these perfectly? Is the float not allowing gas through the needle valve somehow at WOT? Is there a jet or other setting that I can adjust?

To answer your specific questions, no the float levels are not super critical. Eyeball is good enough. Also make sure they drop enough. The only "jets" are the four high speed jets (orifice plugs) in the carburetor bowls. They are not adjustable except by replacement. But they must be absolutely, positively, squeaky clean. And don't be tempted to do anything to them which might scratch or enlarge their orifices.

If it were me, I'd have invested in a fuel pressure gauge temporarily T'd into the fuel hose after the fuel pump, before the carbs to see what the actual running pressure is, rather than going the electric route.

 

[pinchvalve]

I have a pressure gauge on the way!