Metallic clunking sounds when accelerating

HerbieJ

Cadet
Joined
Oct 3, 2009
Messages
19
I bought a used 1994 Mercury Tracker, 3 cyl. 60 hp motor last November. Oil injection pump has been removed. I've invested about $400 in it, adding / replacing little things worn or missing. My efforts have included rebuilding the three carbs, replacing the spark plugs and wires, and verifying the timing was correct. The motor starts and runs, but with a rough idle that carb adjustments don't correct. Big problem though is, when motor is accelerated to approx. half idle, I can hear metallic clunking sounds coming from it, especially when I back off the throttle. There is no apparent engine miss or decrease in rpms accompanying these sounds, but I'm only running the motor in a barrel w/o a prop. This is my first outboard motor and, while I?m familiar with car engines, a two-stroke is new to me. I'm really concerned over the metallic clunking noises I'm hearing though. Compression on all three cylinders is very close to 110. What do you think my problem might be?
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: Metallic clunking sounds when accelerating

I bought a used 1994 Mercury Tracker, 3 cyl. 60 hp motor last November. Oil injection pump has been removed. I've invested about $400 in it, adding / replacing little things worn or missing. My efforts have included rebuilding the three carbs, replacing the spark plugs and wires, and verifying the timing was correct. The motor starts and runs, but with a rough idle that carb adjustments don't correct. Big problem though is, when motor is accelerated to approx. half idle, I can hear metallic clunking sounds coming from it, especially when I back off the throttle. There is no apparent engine miss or decrease in rpms accompanying these sounds, but I'm only running the motor in a barrel w/o a prop. This is my first outboard motor and, while I?m familiar with car engines, a two-stroke is new to me. I'm really concerned over the metallic clunking noises I'm hearing though. Compression on all three cylinders is very close to 110. What do you think my problem might be?


Have you looked into the LU. The noise might even be normal with no load on it. With muffs on and a prop, at least you have an inertial load on it.

The rough idle could be one of 3 things.
1. You thought you fixed the carbs, but didn't.
2. bleed valves and lines
3. reeds

hope it helps
John
 

79Merc80

Senior Chief Petty Officer
Joined
Nov 22, 2007
Messages
673
Re: Metallic clunking sounds when accelerating

Could be the pressure plate in the flywheel. Lightly tap on it with a hammer. If it rattles, then the plate is cracked. Had that happen on a 69 Merc 1250. Thought I was throwing a rod or something.
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: Metallic clunking sounds when accelerating

Could be the pressure plate in the flywheel. Lightly tap on it with a hammer. If it rattles, then the plate is cracked. Had that happen on a 69 Merc 1250. Thought I was throwing a rod or something.

Correct description is flex plate. :D

hope it helps
John
 

sschefer

Rear Admiral
Joined
Nov 13, 2008
Messages
4,530
Re: Metallic clunking sounds when accelerating

Is there lube in the lower unit?
 
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