90 evinrude rattle

[seabasser]

i have a 1998 90 evinrude, 60 degree vee, that rattles from 1/3 throttle on up, especially on decelleration, i've had knocks before and this sounds different, and all i read about the dog clutch rattle says only on decelleration, just wondering if anyone had any ideas.

 

[R.Johnson]

Re: 90 evinrude rattle

Does the engine rattle, both going up, and down with the throttle.

 

[seabasser]

Re: 90 evinrude rattle

no, once it's over 1/3 throttle it rattles all the time, but it's louder when i pull the throttle back.

 

[flabum]

Re: 90 evinrude rattle

Check that your engine cover clamps are tight. I had an older 140 that sounded like it was comming apart and I sound one of the hood clamps loose. Adjusted the clamp and all is well.


If that is not the case, you could have some real issues. Check the timing. Also, how does it run at full speed? does it turn up to the required RPM? It could also be running slightly lean.

 

[R.Johnson]

Re: 90 evinrude rattle

Finding a noise can sometimes be a hard call. It could be most anything, but start by checking the gearcase oil. Gear damage can telegraph upwards, and sound like a power head problem, check the flywheel also.

 

[Texasmark]

Re: 90 evinrude rattle

Not an OMC expert, but on the Clutch Dog Rattle, you mentioned, it is probably just a Merc issue, not OMC. OMC uses a lever to move the dog back and forth in the process of shifting gears. Merc uses a 3 position detented cam at the front of the lower unit which pushes on a cam follower which is spring loaded against a pin in the dog. The spring is the problem there (my opinion).

On deceleration, (every time you decelerate) the prop is turning faster than the engine so you get an overrun condition and for that reason the face of the dog and the rear of F gear are sawtoothed shaped so that they can slip. However, when the engine is powering the prop (acceleration-constant speed) the vertical parts of the sawtooth engage and there isn't (shouldn't be....but could be due to wear) any slippage.....but if you had some it would surely clunk/rattle.

Since a cowling could be a problem, you might remove it. Then get someone close to the engine (safely) while operating the engine where the noise is present.

A tube, like paper towels come on, will help in isolating the noise, but metal transmits sound such that, as stated, it is sometimes to isolate the origin.

Good luck,

Mark

 

[Dhadley]

Re: 90 evinrude rattle

It's not uncommon for some 60* motors have what the eingineers refer to as "decell knock". On hard decelleration you'll hear a loud knocking sound that will go away if you hit the primer. It doesn't hurt anything but it's very annoying.

However, you shouldn't hear it at a steady rpm. Make sure you have the right plugs and you're using 87 octane. We'll assume the heads have not been cut nor the carbs rejetted nor the timing changed from factory specs.

 

[seabasser]

Re: 90 evinrude rattle

i found the problem, the shift cable adjustment was way off, i lacked a good 3/4 to 1 inch from going all the way in forward. i put the engine in gear, and tried to turn the prop i turned the motor over then it slipped by, i adjusted the cable, and now it seems to be good. the place i bought the motor from insisted on installing it, what i fine job they did.