2005 Mercury Optimax 135 rattling and shaking at low speeds

Burro237

Seaman Apprentice
Joined
Jul 29, 2012
Messages
37
~~I recently changed the spark plugs on my motor. Once the job was done I hooked up to the water hose and started it up...started up great, but when I shifted into gear at low rpm the motor started rattling and shaking, almost like something was rattling around in the gears. Its not a continuous rattling and shaking, its like it runs fine for a few seconds, then clack- clack- clack for a couple seconds, with a lot of motor shaking, then back to fine for a few seconds, then again, etc. When I accelerate to higher rpm, no rattle. No rattle in neutral either. Just low rpm in both forward and reverse.
I suspect maybe I messed something up during the spark plug change, but I cant imagine what. My only other guess... a couple of weeks ago, my daughter accidently shifted the throttle into reverse while the boat was not running. I shifted back into neutral and started it back up just fine, but ever since then, the throttle has not seemed the same, sort of sticky. It may have been rattling at low speeds but I just didn't hear it because I was actually on the water, instead of hooked up to a hose.. Any suggestions?
 

407pilot

Cadet
Joined
Aug 10, 2013
Messages
8
My 01 mercury 90 was doing the same for a long time . Turn the idle up a little that way when you shift into gear the engine doesn't drag down so much. That is what is causing it enough fuel to keep itrunning, just not enough to keep it smooth in gear.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,370
Stainless prop ?------Might just be the prop causing the rattling on the clutch dog as there is no load on a hose.----Take it off and run it again.
 
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