1971 Evinrude 60 HP Motor Knock

Im not sure where to start with this as I haven't been able to put the boat in the water and test it to see if it knocks all the time or not or just in nuetral or whatever. I dont think this knock is normal. Here is a video what do you guys think? Should I tear the head off and check the pistons? The noise sounds like it is coming from the exhaust side mainly. Possible Seal?

http://s1128.photobucket.com/user/disturbed1482/media/1970 Evinrude Motor/Knock_zpsda83e87c.mp4.html

Re: 1971 Evinrude 60 HP Motor Knock

check compression. If one cylinder is lower than the rest......
If not, take off the lower unit and put the hose on the water tube and run it again. At least you'll know the problem is either in the powerhead or lower unit. I can't tell from the video. It could even be a magnet loose under the flywheel and rubbing.
Wish I could help more,
JBJ

Re: 1971 Evinrude 60 HP Motor Knock

That was a great help Thanks for the info, Im going to check tonight and do what you suggested and take it from there. I have the LU off right now anyway waiting for a Water Pump so half the Procedure is done. Any why would it make that noise if one cylinder is lower than the other? This is a 3 Cyl if that makes any difference.

Re: 1971 Evinrude 60 HP Motor Knock

The noise could be a bad wrist pin in a piston. The bad wrist pin would probably allow the piston enough slack to wallow out the hole and show bad compression. I'm no expert on this. I've had seen a bad wrist pin on a couple of outboards and they both showed bad compression. I've had a crankshaft main bearing cage come apart and it also resulted in very low compression on the cylinder that got cage pieces between the cylinder and the piston. A slight tick of a loose wrist pin probably wouldn't cause bad compression, but if you're hearing the knock on idle and it's from a bad wrist pin you'd almost positively have bad compression.

You could take a wrench and turn each piston until right before top dead center and stick a clean screwdriver in the spark plug hole and push down. Then go barely past top dead center and push again. If you feel significant slack when you push down on the piston compared to the other cylinders, it's probably a bad wrist pin.
This would be one of the worst case scenarios, so don't get all worried just because you hear a noise.

How does the engine run? Smooth at all speeds? If so, it's likely not a big deal.
JBJ

Re: 1971 Evinrude 60 HP Motor Knock

A lower unit can be bad and the sound will travel up the D/S to the power head. Been there.

Re: 1971 Evinrude 60 HP Motor Knock

Yea thats funny that you say that about the compression I took a reading after I first purchased the boat and it read

#1 105-110psi

#2 125psi

#3 130 psi

Ill have to run the boat with the LU off and see if the noise goes away and take it from there I was planning on that tonight but the weather turned crappy and I got lazy haha. Ill try that first thing in the morning

As far as how it runs it seems to run decent but it sounds like it may have a slight miss but I cant tell for sure I think it should run smoother than it does when I gas it up it just sounds a little off to me for sure gas is mixed right at 50:1 so I think Ill check for spark at some point. I need to get one of those air gap spark tools

Re: 1971 Evinrude 60 HP Motor Knock

It didn't sound to me like it was running on all three cylinders - maybe even only one. That might give the impression of a knock as it's dragging the other cylinder(s) through the motions. Might try either pulling a plug wire or stuffing a rag in a carb, one at a time to note any difference while it's running. A power drop would indicate it's running on that cylinder.

Re: 1971 Evinrude 60 HP Motor Knock

Ok Thanks Chinewalker. I will check that out also.