75 HP Merc. Runs rough @ idle and stalls (need Help Please)

[Petrip]

I just bought a used boat with a 2000, 3 cylinder 2 stroke, 75 hp Merc. Outboard. The engine has 26 hours on it, has not been used in the water since 2002, and previous owner started the boat once a year since it's been in heated storage. I drained all the old gas and put in new. I also put in new plugs. THe boat runs very rough at idle and lower speeds (sometimes stalling) , but seems to be better @ higher RPM'S. I checked the plugs after running figuring it was only running on 2 cylinders, and the plugs all looked equally new and slightly wet. Any suggestions would be appreciated !

 

[achris]

Re: 75 HP Merc. Runs rough @ idle and stalls (need Help Please)

Hi Petrip,<br /><br />Welcome to iBoats.<br /><br />Have you tried adjusting the idle mixture? What plugs are in? I ask because I once fixed a poor idle problem by removing the wrong plugs (used in the 4 cylinder engines) and replaced them with the right plugs. Funny about that, ah.<br /><br />Chris.........

 

[oregonfish]

Re: 75 HP Merc. Runs rough @ idle and stalls (need Help Please)

A pinhole in the fuel pump diaphram could cause this too, if fuel is entering through the vaccum line. At higher rpm's, you are able to burn the extra, but at lower, it is slightly rich.

 

[Vlad D Impeller]

Re: 75 HP Merc. Runs rough @ idle and stalls (need Help Please)

It could well be that some varnishing has occured during the time that the motor was laid up, get the carbs cleaned and adjust the idle mixture and see what happens.<br />It would be prudent to replace the fuel pump Diaphrams and the impeller as well.<br />good luck