TOPIC: Backfire

So while out last night boat was running about normal but seemed a little light on take off and while running about half throttle it backfired a few times like a popping sound and then it went away? what usually causes something like that.

Ignition is my thought without hearing it.

It only made the popping sound 8-10 times and each one was a single pop. i did let the tan that i was running that night sit with gas in it for a few weeks and some of it was regular pump gas. i went back to the tank last night that was good gas from the marina and had no problems with it per say.

First guess would be water, doesn't take much.

63 Sabre wrote:

First guess would be water, doesn't take much.

Have agree here. Water or ethanol/water mix in the bottom of the fuel tank. Don,t ignore it. Clean the tank and empty the fuel bowls and flush the system with clean fuel.

when it happened I switched tanks and have not run that one sence. I am going to run it all through the motor this weekend and then I will switch back to the old tank with the known good gas. when it comes off the dock this year I am doing all new fuel lines and pump rebuilds ect. this motor is a runner just needs some updating to make it pur.

I am going to run it all through the motor this weekend and then I will switch back to the old tank with the known good gas.

Are you thinking of running the (known) bad gas through the Merc this weekend!? (I've re-read the post three times, had another cup of coffee, just to make sure I'm not mis-understanding.)

DON'T DO IT! Get that crap out of your boat and as far away from the Merc as possible. Use it for weed killer, lawnmower gas, or something. After all the time and money you've spent getting this fine outboard in order I sure wouldn't take a chance - severe engine damage can result.

Sorry for the rant Disco, just don't want to see you have a bigger problem trying to save a few dollars on old, bad gas.

I think he is trying to test the old tank with new gas. Not a good idea. If the old tank is restricting fuel you do not want to find out the hard way. Stick with the tank you are not having trouble with. Good idea to change the fuel lines during its winter lay up. old fuel lines can release rubber debris and block a jet.

Well i dont know what the popping sound was but i have long sence run the questional gas through it and it has not run any worse. It still starts great and still burns mad gas. I have probably run about 60 gallons through this motor. I cant wait to figure out why it is running ruff on the top end

can't you bring it back to tim? he's only an hour or so drive from you.

Tim has been out of commission for a couple months and he did not think he would be back into the shop until November. I have been at work a lot so there is no time for waiting. the boat is in a dock just waiting to be run. I am going to have to get the floor and stringers and transom done over the winter. I want to upgrade to a bigger boat and more modern and keep this one for the nostalgia concept.

discocurly wrote:

Well i dont know what the popping sound was but i have long sence run the questional gas through it and it has not run any worse. It still starts great and still burns mad gas. I have probably run about 60 gallons through this motor. I cant wait to figure out why it is running ruff on the top end

That would worry me. Running rough at the top end is dangerous, if its lean, its toast.