Identify this knocking noise *VIDEO*

[rockfordhx]

Help.

My evinrude 25HP is making a knocking noise and I dont know where it is coming from or if it is serious. The motor seems to run fine but I dont want to cause anymore damage to it by continuing to run it. Here is a link to a video that I took of it yesterday. The knocking noise seems to increase in frequency as i gave it more throttle.

Any help will be greatly appecriated.

I recently have cleaned out the carb and replaced spark plugs.


http://www.youtube.com/watch?v=76vnumecnvk

 

[bktheking]

Re: Identify this knocking noise *VIDEO*

What plugs did you put in it?

 

[Brianjason6]

Re: Identify this knocking noise *VIDEO*

Not to sound novice but, usually when I hear that noise something in my recoil is hitting. Did you try to slowly pull the rope a couple inches and let it back in? It may be sticking just enough to cause chatter. Doesn't sound metal to metal.

 

[bktheking]

Re: Identify this knocking noise *VIDEO*

I was going to say that as well, pull the recoil off and rope start it.

 

[rockfordhx]

Re: Identify this knocking noise *VIDEO*

The plugs that I put in are QL77JC4.

I did not think about pulling the cord a little. I will try that and keep you guys posted. I just pulled off the lower unit last night so once that is back on I will start it back up.

Is there any harm in running the outboard with muffs on but without the prop?

 

[restornator]

Re: Identify this knocking noise *VIDEO*

Is there any harm in running the outboard with muffs on but without the prop?

it would make no difference.

I agree with others, it sounds like something in the recoil. could be the starter pawl..

 

[rockfordhx]

Re: Identify this knocking noise *VIDEO*

So I got the lower unit back on and everything back running.

While running the motor in neutral and at idle, I pulled out the starter rope slowly until I had it all the way out. This did not make any difference in the knocking sound.


Any other ideas?

 

[G DANE]

Re: Identify this knocking noise *VIDEO*

Sorry to say, but I had one that somehow got a washer in thru the carb, chewed it in parts, knocked it firmly in the top of a piston and started banging it against the cylinder head when it ran. Unscrew both sparkplugs, light thru each sparkplughole with a penlight when the piston is in the lowest position and examin piston tops. Let us know what you find. Could be a magnet hitting too, but sounds like internal problem.

 

[rockfordhx]

Re: Identify this knocking noise *VIDEO*

thanks for the idea G Dane. Last week I took the cylinder head off and did not notice anything strange stuck to the cylinders. Everything looked pretty clean. The only thing I noticed was a little bit of oil in the lower cylinder.

 

[lindy46]

Re: Identify this knocking noise *VIDEO*

Remove the pull starter and rope start it by wrapping a rope around the flywheel.

 

[jonesg]

Re: Identify this knocking noise *VIDEO*

Pull the sparkplugs, use a dowel to follow the piston thru its travel as you rotate the flywheel by hand, don't use and pressure on the dowel, just follow the piston with contact so you can feel where it is.
Then as it goes ATDC stop turning and push down on the dowel, there should be no play , if you can push the piston down without the flywheel turning theres slop in the wristpin or crank bearing end.

Do it with each piston.
If all is good then its something else.

 

[rockfordhx]

Re: Identify this knocking noise *VIDEO*

thanks, I will try both of those...

What is ATDC though?

 

[Fl_Richard]

Re: Identify this knocking noise *VIDEO*

Above Top Dead Center. - The point where the piston stops rising in the cylinder and before it starts going down.

 

[bktheking]

Re: Identify this knocking noise *VIDEO*

Try pulling off a wire and running it to see if the sound changes and switch wires to see if it is still there. Have you inspected under the flywheel?

 

[ezeke]

Re: Identify this knocking noise *VIDEO*

thanks, I will try both of those...

What is ATDC though?

Usually refers to: After Top Dead Center

 

[Fl_Richard]

Re: Identify this knocking noise *VIDEO*

I stand (or sit) corrected - Thank you! Ez

 

[bob johnson]

Re: Identify this knocking noise *VIDEO*

Id shim teh rope starter assy up one washer at each mount...

at first id guess the fly wheel it tapping a spot on the underside of that assy.

on the video is was gap no gap gap no gap...

of course the noise if once a revolution, but a rod would be the same incidence.... once a revolution

hope it helps ..maybe!!

id love for that to be your problem , rather than something inside


after reviewing the video again, i can see from the other side of the motor, there isnt any interferance...so forget my idea ha ha!!!!!!!!!

bob

 

[bob johnson]

Re: Identify this knocking noise *VIDEO*

Pull the sparkplugs, use a dowel to follow the piston thru its travel as you rotate the flywheel by hand, don't use and pressure on the dowel, just follow the piston with contact so you can feel where it is.
Then as it goes ATDC stop turning and push down on the dowel, there should be no play , if you can push the piston down without the flywheel turning theres slop in the wristpin or crank bearing end.

Do it with each piston.
If all is good then its something else.

you know i have a knock in a 90 hp ocean pro...If I did your tests and all is good..IE I can't move the piston once the move goes over top dead center jst a tad...

then what else could make that knocking noise?

I have a OIS 60 degree looper...

also for the OP where would you suggest to look for another source of this internal know???

magnets under the flywheel??

will they make this much noise and still allow the motor to run?

thanks

bob

 

[rockfordhx]

Re: Identify this knocking noise *VIDEO*

Thanks guys.

I will pull the rope start assembly off this weekend and try to rope start it without the assembly. If no luck I will test for play in the piston using the dowel method. Lastly I can pull the flywheel and look for any rubbing.

If nothing works I will try to post another video.

 

[Tig]

Re: Identify this knocking noise *VIDEO*

I had a geek flash and decided to analyze the sound. It occurs at a frequency of 960 RPM, which is probably your idle speed. That makes me think wrist pin/crank bearing.
The acoustics of the recording may be fooling us because it does not sound like a crank noise to me so I'll post my guess as wrist pin.