Hi everyone. we recently picked up a 1974 mercury 402 40 horse to put on a boat we enherited from my father in law. We took it to the lake to try it after putting it on the boat. We ran at low speed far a minute or two and then tried to kick it up. We gave it a good amount of gas and got up on plain with everything good and the motor was not wide open yet. after 30 seconds the motor just instantly shut down and died. It would start right back up but would no longer go past about a quarter throttle without stalling. Once you hit the quarter throttle mark its like a switch it just shuts down or wont power past that. It doesnt mater if its fast or slow acceleration once you hit that point in the throttle it will start to act like the fuel is being shut off. If I take it out of gear it will rev up just fine. if you try a whole shot it will start to respond for a split second then stall.
After this I took it into the shop to be checked. It got ignition checked, new plugs, carbs adjusted, compression 140lbs on bolth, new water pump. It ran good for them. took it back to lake starts and idles better than before, but still wont power past the 1/4 to1/3 throttle twist. Does anyone have any ideas? I was wondering if there is a high speed carb jet blocked or something, but then I am not a mechanic.
Thanks all?
Robert
After this I took it into the shop to be checked. It got ignition checked, new plugs, carbs adjusted, compression 140lbs on bolth, new water pump. It ran good for them. took it back to lake starts and idles better than before, but still wont power past the 1/4 to1/3 throttle twist. Does anyone have any ideas? I was wondering if there is a high speed carb jet blocked or something, but then I am not a mechanic.
Thanks all?
Robert