Engine runs rough at High RPM's 40 HP Evin

[boss5184]

My 40 HP Evinrude run fine til about 2500 -3000 rpms. Then it tries to red line.I have pull the thottle back .It starts and idles fine. Any ideas?

 

[F_R]

Re: Engine runs rough at High RPM's 40 HP Evin

By red line, you mean it races like it is slipping? Does it make any terrible grinding noises when it is doing that? If not, then it is either cavitating or the propeller hub is slipping. Most likely the hub.

To find out, make a mark on the plastic prop cap and another on the propeller itself, aligned with the first one. Run the motor till the suspected slippage occurs. Stop the motor and see if the marks are still aligned. If not, it has slipped. Either replace the prop, or have yours re-hubbed. You can't re-hub it yourself, you have to send it to a prop shop.

 

[boss5184]

Re: Engine runs rough at High RPM's 40 HP Evin

It does this out the water on a hose.

 

[F_R]

Re: Engine runs rough at High RPM's 40 HP Evin

What??? Stop doing that before you blow it up. Never run above fast idle on the hose. It is doing what is called runaway. It was meant to run on a boat in the water.

 

[boss5184]

Re: Engine runs rough at High RPM's 40 HP Evin

It does the same in the water.

 

[F_R]

Re: Engine runs rough at High RPM's 40 HP Evin

You lost me. By in the water, do you mean in the water and in gear or in neutral? If in gear, see my previous reply about checking for a slipping prop hub. If you are still revving it in neutral, see my previous post about don't do that.