Engine Knock: Now what?

[fixmyevinrude]

1994 Evinrude 200HP LE 200 SLERS

After a rebuild 2 years ago with 6 new pistons installed and one new sleeve everything seemed to be going pretty well untill last weekend. Engine was running fine then developed a very slight ticking or knocking noise. Noise dissapeared and then came back as a loud knocking noise as I was driving it up on the trailer. Put back in water and was knocking lightly as I idled it around. Not wanting to risk more damage I took boat home and did a compression check which checked out pretty good with compression between 92psi and 100psi on 5 cylinders and the number 4 cylinder checking out at 88psi which is the cylinder that was resleeved. I am frustrated. Any ideas on what is wrong and how to check and verify. I am thinking I have a bad rod bearing. I hope I am wrong and it is simpler. The engine has about 15 hours since rebuild. I would have thought if I put it togrther wrong it would have showed up by now. I don't believe it is spark knock.

 

[stroker24]

Re: Engine Knock: Now what?

since you replaced the engine with 6 new pistons that could have raised the compression at a higher rate say 10:1 or 11:1 i would try a higher octane rating 93 and if that doesnt work then it could be a ticking valve thats stuck

 

[jonesg]

Re: Engine Knock: Now what?

Do a compression test.
Then test the rods by following the top of piston with a dowel as you rotate engine by hand, stop after it passes TDC push down on the dowel, if theres any slop in the rod bearing you will feel a click.

 

[tashasdaddy]

Re: Engine Knock: Now what?

make sure nothing is hitting the flywheel.

 

[fixmyevinrude]

Re: Engine Knock: Now what?

Do a compression test.
Then test the rods by following the top of piston with a dowel as you rotate engine by hand, stop after it passes TDC push down on the dowel, if theres any slop in the rod bearing you will feel a click.

Compression checked fine. I will the check rod bearings in the manner you described. I also just got a mechanics stethoscope and I will listen to the engine with it. Thanks, thats the kind of info I'm looking for.

 

[bob johnson]

Re: Engine Knock: Now what?

I had a knock...motor ran great, just knocked....not super loud but enough to think, you cant trust it in rough weather, to not finally die...

tried the piston push, couldnt get them to budge at all!!!! nada....

compression was great..

finally took it apart and it was piston slap... one piston was way out of round... and undersize....and was galling the skirt...not bad yet....but it wasnt going to fix itself..

do these two strokes respond to higher octane???

I was thinking I read or was told 2 stroke compression is different than four stroke....

can you get detonation pinging in 2 stroke outboards??


curious

bob

 

[fixmyevinrude]

Re: Engine Knock: Now what?

make sure nothing is hitting the flywheel.

That also could be a possibility. If a magnet came loose I would think it could make a racket. I will inspect it closely. Thanks for the help.

 

[fixmyevinrude]

Re: Engine Knock: Now what?

I had a knock...motor ran great, just knocked....not super loud but enough to think, you cant trust it in rough weather, to not finally die...

tried the piston push, couldnt get them to budge at all!!!! nada....

compression was great..

finally took it apart and it was piston slap... one piston was way out of round... and undersize....and was galling the skirt...not bad yet....but it wasnt going to fix itself..

do these two strokes respond to higher octane???

I was thinking I read or was told 2 stroke compression is different than four stroke....

can you get detonation pinging in 2 stroke outboards??


curious

bob

Have not thought of that and I hope its not but certainly something I will have to look into. Is there anyway to check without tearing down the engine? Would I be able to see it by removing the heads?

 

[Dhadley]

Re: Engine Knock: Now what?

Honing, boring or resleeving will not raise compresision ratios. It's also not a good idea to run 93 octane. Make sure you have Champion plugs too.

 

[bob johnson]

Re: Engine Knock: Now what?

Have not thought of that and I hope its not but certainly something I will have to look into. Is there anyway to check without tearing down the engine? Would I be able to see it by removing the heads?

the first I could see it was after I took the carbs and then the intake manifold off...

cant see nothing much from the head side...there wasnt much sleeve wall damage....but you cant see the skirt from the head side...got to look in from the intake

and then you can ONLY see ONE SIDE of the piston...

if you cant find the knock from other sources....that are easier to fix....

IE loose magnet, or something hitting the flywheel...or that the lower unti isnt making the noise.. and sending it up the drive shaft

then you have to tear the motor down...

thanks Dhadley..good to know

bob

 

[fixmyevinrude]

Re: Engine Knock: Now what?

Honing, boring or resleeving will not raise compresision ratios. It's also not a good idea to run 93 octane. Make sure you have Champion plugs too.

I am running champion plugs. I usually run 87 octane in the motor. I know I have read its not good to run 93 octane but I don't know why. I would like some knowledge on piston slap.

 

[fixmyevinrude]

Re: Engine Knock: Now what?

the first I could see it was after I took the carbs and then the intake manifold off...

cant see nothing much from the head side...there wasnt much sleeve wall damage....but you cant see the skirt from the head side...got to look in from the intake

and then you can ONLY see ONE SIDE of the piston...

if you cant find the knock from other sources....that are easier to fix....

IE loose magnet, or something hitting the flywheel...or that the lower unti isnt making the noise.. and sending it up the drive shaft

then you have to tear the motor down...

thanks Dhadley..good to know

bob

Bob you have me wondering about piston slap. I obviously have to do some trouble shooting but I never considered piston slap. What would cause that after 15 hours of good service after a rebuild.

 

[bob johnson]

Re: Engine Knock: Now what?

Bob you have me wondering about piston slap. I obviously have to do some trouble shooting but I never considered piston slap. What would cause that after 15 hours of good service after a rebuild.

I am not sure.... if i were to guess.. Id say overheating

I chimed in because of what I had and what i found it to be....


good luck

bob

 

[fixmyevinrude]

Re: Engine Knock: Now what?

I am not sure.... if i were to guess.. Id say overheating

I chimed in because of what I had and what i found it to be....


good luck

bob

Glad you chimed in. I am wondering if you had piston slap when the engine was cold or hot or after extended runs or if it made any difference?

 

[bob johnson]

Re: Engine Knock: Now what?

Glad you chimed in. I am wondering if you had piston slap when the engine was cold or hot or after extended runs or if it made any difference?

hot or cold.....didnt matter


bob

 

[Faztbullet]

Re: Engine Knock: Now what?

Could be upper bearing as I have seen quite a few fail lately....

 

[daselbee]

Re: Engine Knock: Now what?

Could be upper bearing as I have seen quite a few fail lately....

Exactly, and if you failed to replace the check valve in the recirc line that goes from the #6 crankcase up to the top of the engine when doing the rebuild, you may not have been oiling that upper crank bearing.

Refer to parts listings at shop.evinrude.com, drill to your engine, go to cyl and crankcase section, item number 42.

Try seeing if you have side to side play in the top of the crank by pushing sideways on the flywheel. You might feel it if you are lucky.

 

[daselbee]

Re: Engine Knock: Now what?

So what did you find out? I hate to be left hanging.

 

[fixmyevinrude]

Re: Engine Knock: Now what?

So what did you find out? I hate to be left hanging.

Well I have not found anything yet. I just got home from fishing at Table Rock Lake this past week. We ended up tacking my brother in laws boat. Will check mine out soon and let you know. As far as the rebuild goes I did not replace the check valve in the recirc line. This noise is a tap tap tap type knock that increases as the rpm's increase. Its a hammering type knock. Does that sound like a bad bearing? Regardless I will see if I can feel any play through the flywheel. I really appreciate all the great help on this forum. It truly is invaluable.