knock knock knocking at the knock experts doors!

[bob johnson]

fired up this 1997 evinrude 90hp ocean pro, I bought from a guy who was worried about getting stranded in LONG ISLAND SOUND, because of a slight knock he heard. He said last summer it was present when he bought the boat. He took the boat fishing at least 15 trips during the summer and fall and he cruised with the motor out and back and trolled.....the knock never got worse...the previous owner knew of it...but could'nt explain it.

well i bought the motor cheap because of the knock, thinking the worst thing that could happen is I end up with a parts motor.

the engine had been fogged for the winter so it took a while to get her started....

but fiannly i had it idleing smoothly....and it reved smooth( I didnt rev it much)

there is a knock, but it doesnt tell through the block or the head...it is definatley related to the rpm...it felt like it was coming from the flywheel area.

so i took the cover off to see the timing marks and it seems to be coming from under that spinning pieces with the timing marks on it...and or from the flywheel...

it is a little harder than a clicking...but it really isnt a solid KNOCK..a tapping.

I dont know whats under the flywheel cover or the flywheel.

so I am sking here..is there anything under there that could cause a tapping...

you can not hear it when you rev the motor, because the engine drowns out the sound.

I keep hoping since he took it for so many trips with the miles he put on it all the while the knock was there..that it couldnt have been a rod knock..

it is a nice clean motor!!

hope to hear from some of you guys

bob

 

[CATransplant]

Re: knock knock knocking at the knock experts doors!

Nothing for it but to pull the flywheel and have a look around. Could be a mispositioned component, a loose screw, or a magnet that has come unbonded from the flywheel.

So far, it hasn't probably caused expensive damage. It could, though, at any time. If you check the price of a new stator, you'll see what I mean.

Go to http://shop2.evinrude.com and drill down to your model and check the ignition system blowup drawing.

I wouldn't keep using it with the knock in place, but it's your outboard.

 

[rpnlps]

Re: knock knock knocking at the knock experts doors!

i had a 115 merc tower of power do the same thing.all that was wrong was the starter was getting stuck up in the flywheel .sounded like a blown motor.sounds simple but you never think about that. im sorry about your luck.take care ..scott

 

[bob johnson]

Re: knock knock knocking at the knock experts doors!

i had a 115 merc tower of power do the same thing.all that was wrong was the starter was getting stuck up in the flywheel .sounded like a blown motor.sounds simple but you never think about that. im sorry about your luck.take care ..scott

well its not bad luck...

I knew it had a knock going in. The seller was up front about it and priced the motor accordingly.

this motor normally would run about $3500 and up around here... I paid $700 figuring if it went totally bad that the lower unit would be worth that. And or i could it for parts , because i wanted to eventually get a 90 HP.

from talking to the guy i would estimate that he put over 60 hours on the motor all the while it had this same knock. And the previous owner to him also ran it with this knock.

once I get a full sunny day, Ill pull the flywheel and take a look around.


bob

 

[donnyskz1]

Re: knock knock knocking at the knock experts doors!

I had a knock like that and it turned out to be a loose magnet on the flywheel. With the right glue it will hold for a very long time.

 

[Mas]

Re: knock knock knocking at the knock experts doors!

Get one of those "mechanic's stethoscope" and see if you can isolate the knock. Harbor Freight sells them cheap.

Dylan

 

[wesley pipes]

Re: knock knock knocking at the knock experts doors!

i had thatproblem the other day on a guys boat and found that it was just a loose flywheel nut and the driveshaft was knocking up and down. but if not that my next best guess would be the stator or anything under there

 

[MAW31]

Re: knock knock knocking at the knock experts doors!

for such a cheap and inexpensive diagnostic tool, they are priceless when attempting to isolate source sounds.

 

[kenmyfam]

Re: knock knock knocking at the knock experts doors!

Time to play "dig and look" If it is something simple you got a bargain.

 

[bob johnson]

Re: knock knock knocking at the knock experts doors!

well I finally mounted the motor on my boat and ran it. I ran it a few hours trying to get the trim and jack plate set and check rpms...but the knock SEEMED to be louder... and it didnt sound promising.. I took it to my mechanic and he said it might be a wrist pin. so I went out and bought the samne model motor but in 115 HP this one is a johnson Ocean Runner and I now have the 90 for a parts motor. which is good because I run the boat in the winter and a lot of places are closed more or have limited hours.

so I would be stuck for getting parts, or repairs

bob

 

[wilde1j]

Re: knock knock knocking at the knock experts doors!

I would be looking for a problem with the upper crankshaft bearing, as well as some of the other possibilities others have mentioned. Those stethoscope tools are great, but not much use here, BC you can't get to the important places with the flywheel mounted.