loud knocking noise underway in gear

I have an evinrude 140hp 4cyl (1990) as I way underway engine sounded louder & louder ,sounded just like engine knock, when I slowed down and put it in nutreal engine runs fine, even at high idle no knock but when I put it in gear it sounds like the prop is hitting a zinc. Its my lower unit shot? what should I check first? all input welcom Thanks

 

Have you checked your prop? I'm thinking that something has been bent – could be the shaft.

 

Bagger's on the right track. Methodically check everything, part by part from bottom to top, starting with the prop. Since the noise goes away in neutral, it's probably not engine damage. That leaves lots of drivetrain possibilities; hopefully the cure is just replacing one or a few parts.

 

it might be running a little lean too. I would check fuel system. But check your propeller first. Turn it by hand it might be a bearing .

 

disconnect the coil or fireing meck first then turn by hand,so it dont start on ya,,,,,longliner

 

Wow some real good questions and even better answers.

You will not turn a 140 over by hand grasping the flywheel ,--take the plugs out if you want to do that.

Personally I think you've changed the prop and not fitted it correctly???

Iether that or your gear selector linkage has become badly adjusted and its slipping its gear. Hard to tell from your descrption.

Or youve bent it and its touching the leg?

I doubt very much its a bearing as it is a 2 stroke and will have ball bearings,-- they dont fail like white metal bearings.

 

if on the trailer just pull the plugs to drain the lower unit oil
sound travels up the driveshaft and often sounds like engine when it's the lower by checking the oil you'll find out if it's in the lower most of the time
and frosty is right if you've just change a prop it may cause noise if not installed propperly

 

Thanks for all your input. when i reached the ramp to pull it out I had the balls to put in in reverse and no noise at at all , sounds fine so im thinking
foward gear is damaged ( main shaft is like a pinion right? so its good)
, anyone got a 25" lower for a 1990ish evinrude 140 hangin out?

 

Had some time on sunday so I finally pulled the lower unit plug, attached to the magnet was half a gear tooth and numerous fragments. The oil came out lumpy and slow the color of liquid metal , i drained it all into a ziplock bag.
I had a magnet handy so i put it to the bag to see if could gather the fragments, there was so much metal in the oil it was kind a like an old
etch-a-sketch.... So im thinking replacement or total rebuild, can any one recomend a source for either or both .........Thanks

 

for a rebuilt try southwest marine or riverside and one more would be evinrude also offers rebuilt units

 

There must be hundreds of engines lying around with blown top ends,--hundreds. I would think a few phone calls to some local engine shops should come up with something

 

He dont need an engine...he needs a lower unit

 

Well when he finds one there will be a bottom end attached to it.

 

I think it is rubber shock mounts. A big job, yes, but doable.

 

boat knocking noise

you say it runs OK? Well, if the rubber mounts are weak, it will get metal-to-metal in the midsection, in gear. Buy a good service manual, a lifting ring and mounts and engine base gaskets. You can do this.