1975 115 Evinrude. Back fires when starting.

Ok...I have a 115 hp evinrude. Idles fine...Runs through all the rpm's fine...tops out good and will push the boat and never miss a beat when running. Ok here's what i am concerned about. Occasionally when starting it mildly backfires. When this happenes i have to turn the key off and back on and then starts right up and purs like a kitten. Any suggestions on what might cause this?

Re: 1975 115 Evinrude. Back fires when starting.

Out of time? Couple of small things to check. See if the link arm between the timer base and the spark advance lever is still connected. Also, check the flywheel/crankshaft key to be sure it is not sheared.

Re: 1975 115 Evinrude. Back fires when starting.

Scott Brandenburg said:

Ok...I have a 115 hp evinrude. Idles fine...Runs through all the rpm's fine...tops out good and will push the boat and never miss a beat when running. Ok here's what i am concerned about. Occasionally when starting it mildly backfires. When this happenes i have to turn the key off and back on and then starts right up and purs like a kitten. Any suggestions on what might cause this?

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OK, exactly when does this backfiring occur? As you are cranking it? When it starts running? Instantly when you turn the key on? Is it a one-time backfire, or does it continue? First start-up of the day, or subsequent startups? Describe the backfire: A loud bang out the exhaust, or a muffled cough from under the hood?

Secondly, what happens if you don't turn the key off? Will it start and run if you just keep cranking?

Having asked all those questions, I don't think there is anything wrong with it. If there is, I don't think it would run correctly once started. But let's have some answers and we can ponder on the subject a bit. I don't reccommend messing with it without good reason.

Re: 1975 115 Evinrude. Back fires when starting.

F_R said:

OK, exactly when does this backfiring occur? As you are cranking it? When it starts running? Instantly when you turn the key on? Is it a one-time backfire, or does it continue? First start-up of the day, or subsequent startups? Describe the backfire: A loud bang out the exhaust, or a muffled cough from under the hood?

Secondly, what happens if you don't turn the key off? Will it start and run if you just keep cranking?

Having asked all those questions, I don't think there is anything wrong with it. If there is, I don't think it would run correctly once started. But let's have some answers and we can ponder on the subject a bit. I don't reccommend messing with it without good reason.

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It happens when cranking. holding key in start position won't do anything. even letting it go back to run and then trying to crank again wont do anything. have to turn off and back on. one time backfire under hood not violent. it happens periodically not just on first start up. Could it be carburation? i was just checking over the engine only visiual thing i could see was oil dripping out from under the hood. i was on the lake yesterday. i did not unhook the fuel line when i parked it. when it starts it runs fine and seems to have all the power it should. runs very smooth and rpm's out.

Re: 1975 115 Evinrude. Back fires when starting.

What color is the "oil" dripping out from under the hood? Does it look clearish, or black and nasty looking? Does the oil run down the midsection?

Re: 1975 115 Evinrude. Back fires when starting.

emdsapmgr said:

What color is the "oil" dripping out from under the hood? Does it look clearish, or black and nasty looking? Does the oil run down the midsection?

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Greenish. I think its 2ycle. Figured with the heat and not unhooking the fuel line it flooded and the gas evoporated.

Re: 1975 115 Evinrude. Back fires when starting.

And it is clean. Not nasty or black and grimy

Re: 1975 115 Evinrude. Back fires when starting.

Check the movement of the timer base. Sometimes on these older units, the grease dries out and the timer base does not move freely. If the timer base sticks in any advanced timing position, it is possible that you could get a backfire when starting. Also, you may find that the cranking rpm's seem slow and labored. Regarding the oil leak, make sure the airbox drain hose is connected to the hose barb at the front/bottom of the intake manifold. The carbs on these units tend to leak a small amount of fuel/oil-it will run right into the lower cowl if this hose is not connected.