1978 115hp outboard mercury was running great then just died

[thunderbolt1977]

i took the boat out today to go fishing. She started right up i let sit there and warm up for 10 min like normal while i get my poles ready. I headed out from the marina to my fishing spot. As i went to give it gas i noticed it would not open up as i had the throttle all the way down. After i slowed the motor down it just died on me. I tired to restart her and she back fired and wouldnt start. I dont know what could be wrong does anyone have any ideas for where i should start to look.

 

[CharlieB]

Re: 1978 115hp outboard mercury was running great then just died

Start b y testing spark on each plug wire using an adjustable gap tester set to 7/16 inch. Hopefully you will find a hot blue arc on each, if not you will need to download the Ignition Troubleshooting Guide from CDIElectronics support page.

 

[thunderbolt1977]

Re: 1978 115hp outboard mercury was running great then just died

After letting the motor sit for 12 hours i went back to my marina to check on the boat. Now the boat will start back up on the turn of the key but dies after about 3 seconds it is idleing really rough. I had this same problem about a month ago and it just went away on its own. There has t be smnthing wrong with it but dont know what the problem is. Also it is using alot more gas than it was at the begging of the boating season. Any ideas on what it could be and what i should do to test out some theroys. I think it might be water in the fuel so i treated it with sopme of that dry gas but didnt solve the problem please help asi need it running good for my bass tourny this upcoming weekend

 

[CharlieB]

Re: 1978 115hp outboard mercury was running great then just died

A little dry gas will not take out the accumulated water in a fuel tank,

AND, is NOT recommended, there is too much alcohol in todays fuel as is, adding more increases cyl temps and, worse case, can damage your motor.

If you suspect water grab a pie tin or similar container, pull the float bowl plug on one carb at a time, catch the draining fuel, pump the primer bulb to flush out the carb.

LOOK carefully at the fuel, is there any 'beads' laying under the fuel?

If so, you got water in the tank, enough that the fuel pick-up tube can reach it.

Hopefully the tank is not full of fuel. Jack/block the trailer so that the fuel sending unit is over or near the lower side or end of the tank.

Remove the sending unit, taking care not to leak fuel into your boat.

Screw a couple large nuts onto a suitable siphon hose to weight it down, cut a small V notch in the end of the hose such that it cannot seal if abutted against the bottom.

Siphon off the water into a suitable container until you start pulling clean fuel.

Reinstall the sending unit with a new gasket.

Install a water separating filter.

Flush the fuel hoses to be sure no water is left hiding.

Crank it up.