1999 40 HP 4 Stroke Runs Like a Dog

I have a 1999 40HP 4 Stroke Mercury that runs terrible. Each year that I use it, it runs worse. Do not have S/N handy.<br />1) trouble warming up - keeps killing <br />2) after idling for 4 to 5 minutes - kills at increased trottle <br />3) when running okay at 2000 to 2500 rpm - kills when throttle increased to over 3000 rpm<br />4) when finally running at full throttle it starts missing.<br />During the first Summer the dealer advised me to put an ounce of carb cleaner in with my gas refills, and I have done that with every fill ever since. I have also been using Sta-bil and now SeaFoam with every refill. Have used non-ethonol gas for the past year. Motor gets properly winterized every fall before storage.<br />Motor was inspected by an Authorized Mercury Service shop last summer. They recommended replacing the jets at an estimated bill of $600. When I asked them what I need to do to prevent it from happening again after I spend the money, they didn't have an answer. It did run better after they ran it with high concentration of carb cleaner, but problems came back as it was used after that time.<br />Anyone know if there were any manufacturer's problems with 4 stroke motors that year?<br />Any other good suggestions other than dumping it?

Re: 1999 40 HP 4 Stroke Runs Like a Dog

try removing and cleaning the carbs, fuel pump and lines. then run a fuel system vacum check to test for any restrictions between the engine and the tank, four strokes are rather touchy with carbs.

Re: 1999 40 HP 4 Stroke Runs Like a Dog

Gentleman Jim,<br />I just bought a 2001 whaler with a 40 four stroke. It idles great and will pull 5500 at full throttle. However, trying to get from 2200 to 5500 is a real bear. Move the throttles very quickly and it will not die. It does die every time coming off full throttle.<br /><br />It seems as though I have a sub set of your problems. I have been though the carbs, checked the enrichment valve, replaced plugs and sync'ed the carbs. It runs just a little better.<br /><br />Did you every find an answer?