detonation?

[GKT]

1981 mercury 200...

when im out on the water and increasing speed itll act fine until i get to a little bit over 10mph then it will make a kind of metallic clinkin noise...but if i give it a little more gas itll stop...is this detonation i hear? cavitation?

 

[verado7]

Re: detonation?

having a tach reading would be better than boat speed but - if it is detonation : check your idle mixture ( might need richening)
check for 4-5 volts on trigger wires ( disconnected while cranking)
try a higher octane fuel
faulty primer bulb or fittings at tank and motor
carb needles sticking ( rebuild carbs) and fuel pump
and set floats to proper height .
re-set fuel; mixture screws to the rich side

 

[bobkyle2]

Re: detonation?

i wonder if you are just talking about the i guess thats the power band part.... my mercury does that...it gets really loud at one part i beleive thats were the power band comes in... when its planeing off my buddies always say it sounds like its going to fly apart ... his 150 merc is alot quieter being alot newer

 

[CharlieB]

Re: detonation?

Detonation is a serious problem which destroys pistons.

Definately clean your carbs and be certain float heights are set correctly.

Link'n'Synch to ensure timing is correct.

If the condition persists afterwards, I would suggest running the boat up to the point it makes this 'noise' and immediate kill the ignition, remove the spark plugs and inspect the plugs and piston tops to see what color/condition they are.

Detonation will remove any carbon/blackening on the piston.

Repost your findings.