help with 30 hp evinrude knocking noise

[MAKO72]

I have a 1989 30 hp evinrude. After my last trip out the motor developed a knocking noise. Its not a steady noise and when it knocks the motor seems to miss and jolt to the side a little. The noise is not very detectible at idle but happens more frequent at higher rpm. I checked the compression and had 125 and 123. The same day I heard the knock the motor was very hard to get started It would only start if I sprayed carb cleaner in the carb. Could these two problems be related? Any help ideas or tests I can try to help determine the cause would be greatly appreciated. Thanks in advance.

 

[alcan]

Re: help with 30 hp evinrude knocking noise

Hello Highlines<br />I am just guessing here. But it sound to me like it might be running a little on the lean side. I would service the carb and the entire fuel system. Might be a carbon build up as well. You could try a decarb treatment. I would check all the tune-up stuff first.

 

[G DANE]

Re: help with 30 hp evinrude knocking noise

Hi Highlines<br /><br />There is a little possibility it can be a worn cranck/rod bearing.<br /><br />With motor off and hood off, ignition OFF, Sparkplugwires OFF, try to cranck motor SLOWLY, by turning flywheel by hand. You can feel by mechanical resistance the pistons moving with. You can also feel a little play between cranck/pistonrods at top and bottom deadpoints. Remember to save impeller, only turn the right way. Does play feel even at both cylinders. If you wrickle with flywheel at both deadpionts, try to see how many "starter teets" the deadpiont is, is it equal on both cylinders ?. Do you have more than 1 - 1 1/2 toots on one of them. ? Let us know

 

[MAKO72]

Re: help with 30 hp evinrude knocking noise

Thanks for the replies. First I did try what Alean suggested and adjusted the carb. The motor started and the noise seems to be gone(this was done in the driveway not in the water). I am still a little nervous because I don't understand how running lean would make the noise it had if you could explain that would be great. Second I just tried the test G Dane suggested if I turn the flywheel one full turn it gets to a point where ther is just about 1 to 11/2 teeth of play if i turn it another full turn I get to this point again with the same amount of play. I dont know if I did that correct or if it should be every half turn. Thanks again for your advise any other suggestions would be great.

 

[MAKO72]

Re: help with 30 hp evinrude knocking noise

Thanks for the replies. First I did try what Alean suggested and adjusted the carb. The motor started and the noise seems to be gone(this was done in the driveway not in the water). I am still a little nervous because I don't understand how running lean would make the noise it had if you could explain that would be great. Second I just tried the test G Dane suggested if I turn the flywheel one full turn it gets to a point where ther is just about 1 to 11/2 teeth of play if i turn it another full turn I get to this point again with the same amount of play. I dont know if I did that correct or if it should be every half turn. Thanks again for your advise any other suggestions would be great.

 

[G DANE]

Re: help with 30 hp evinrude knocking noise

Highlines<br /><br />1 to 1 1/2 teeth play doesnt sound bad. The test should be done every 1/2 turn if you want to compare cylinders. But a lot of these motors have some rodbearing play, especially when cold. I dont think this is your problem, but try to compare. Be sure it doesnt start.

 

[alcan]

Re: help with 30 hp evinrude knocking noise

Hello Highlines<br /> A too lean condition can cause a miss,sneese,etc or detination, ping,nock. This lean condition can be caused by, Air leeking into the system, via hose,gasket,connector, or VRO system. Can also be crud in your carb or a restriction else where in your fuel system. If you only adjusted your low speed needle I don't think you have solved the problem. I hope I am wrong. Also you didn't say if your motor was manual or elect. As there can be issues in the priming system as well.When I said service I ment to remove and clean and inspect and repair if nessary. Let us know how it tests out on the water. Good luck have fun.

 

[rolmops]

Re: help with 30 hp evinrude knocking noise

Hello.<br />Your knocks may come from a very different corner altogether.And by what you say it might be well worth checking this angle as well.It is quite possible that your clutch dog gets thrown in and out of gear because the gear shifter has a loose bolt or a streched out tired bolt in it.What happens in these cases is that usually at relatively high rpm's all of a sudden the gear disengages into neutral and then with a bang or knock gets re-engaged.You can imagine what this does to your forward gear(the expensive one)and your clutch dog. When the engine disengages it will jerk to the right for a split second and upon re-engaging it will go back to normal.the screw in johnson engines responsible for this problem is often in the top of the exhaust housing and in order to get to it you may have to take your power head off.Let's just hope that I am wrong ,but something tells me that this is your problem.<br />Good luck.

 

[MAKO72]

Re: help with 30 hp evinrude knocking noise

The motor is an electric start. Alean, I had rebuilt the carb. about two months ago so that should be fine. Now that you mentioned priming today when I was testing it out I did notice that the primer bulb wouldn't get hard I could just keep squeezing and it wouldn't change I looked around and didn't see fuel dripping anywhere it almost seemed like the fuel was just returning to the tank. The motor was in neutral when I first heard the noise so I don't think it would be the clutch dog. Thanks again everyone for your help.