Backfire or clunking noise>>> not sure???

[alternative]

Upon take off and idle down..there is this noise that sounds like a clunk...but it also sounds as if it could be a backfire..cant really tell which since im usually driving while this happens.. once im up on plane and about 3500 rpm it is smooth.. as soon as i lower speed to idle it pops or clunks.... and then again on take off (take off slow or fast..still does this noise????? engine tune up(plugs/wires/elctronic ign--relpaces points/cap rotor(earlier this year)/fuel filter/ and compression test done..ok----- 305 omc i/o 1988............... otherwise boat runs ok idle is still rough...? should i change the small fuel filter at the carb????

 

[Elk Chaser]

Re: Backfire or clunking noise>>> not sure???

Worth a shot, Yes.<br /><br />You can run the boat alone with the engine cowl removed and then it will become obvious if you have a backfire or not.