Lots of Backfire!!!!!! why

[alternative]

Yesterday i went out for a little ride and boat was a little hard to start at first... it sat for 2 weeks at marina. Once running it was smooth, got out to a spot and shut down to fish a little..<br />Start again and drove to another spot.. while driving at about 3k RPM i noticed a popping at the engine compartment.. had a friend open while driving and it was backfiring alot.? slowed down and it continued ..was especially loud when take off to WOT. Decide to pull in marina.. and at no wake speed 800rpm it was fine no backfire ..seems it was only when under load also? im confused.. <br />88 OMC 305 cobra... recent plugs, coil, fuel filt, new ignition(elec)replace points, set timing correctly, compression check --all within 2 months ago. Why is this so suddenly and continuously backfiring> only while driving and over1000 rpms>> was ok two weeks ago THANKS

 

[rodbolt]

Re: Lots of Backfire!!!!!! why

hello<br /> several things can cause a backfire through the carb. sticking intake valve,broken outer valve spring, over advanced ign timing, lean running carb and the kicker is water leaking in from a bad riser. you must find the cause because all of the above can kill a motor.valve train problems can usually be found with a vacum gauge and some experience interpeting the readings, lean running can normally be found by inspecting the spark plugs, timing is easy to check with a timing light but must be done at the rpm and load that the problem is occuring, water intrusion sometimes is a little more dificult but normally the plugs will tell you.<br /> good luck and keep posting

 

[deputydawg]

Re: Lots of Backfire!!!!!! why

My guess would be either the coil or other ignition parts you put on are bad or the carb has a problem. <br />Usually if it is a valve problem, or anything serious it will pop and backfire at all speeds and loads. Where it started after sitting it sounds like a lean fuel condition. I would check compression, and verify the timing and spark then look for the fuel problem. If it all ran good after the electrinic repairs you spoke of, the next step is the fuel.

 

[Don S]

Re: Lots of Backfire!!!!!! why

Might check the firing order of the plug wires. If you got a couple crossed it would backfire a lot.

 

[tommays]

Re: Lots of Backfire!!!!!! why

do you have 10% ethanol blend in your area scince it came to long island i have much more problems with water in the fuel<br /><br />tommays

 

[deputydawg]

Re: Lots of Backfire!!!!!! why

The thing I keep going back to, it ran good.....parked 2 weeks....ran bad. Did someone mess with it while it was at the marina?

 

[alternative]

Re: Lots of Backfire!!!!!! why

yea ran fine..although i should say.. it would backfire in the same conditions as above .. however not as frequently. Guess i should start with a fuel filter..? then chck =all spark plugs and check for spark>>>???? and what would cause this to run to lean all of the sudden????

 

[deputydawg]

Re: Lots of Backfire!!!!!! why

Dirt or water in fuel, bad gas, tarnish buildup in carb, cracked carb gasket sucking air, who knows why these things pick the times they do to go. <br />Make sure dist. cap is good, no white buildup and no moisture.<br />Did it pop a little before and after the electrical componants you changed? If fit did, it could is probably a carb problem that has been slowly going downhill. Sitting idle may or may not have anything to do with it. Start with fuel and good luck.

 

[Bondo]

Re: Lots of Backfire!!!!!! why

Guess i should start with a fuel filter..?

Ayah................. <br />

and what would cause this to run to lean all of the sudden????

Water..........<br /><br />No Doubt you've got it.........<br />Question is, How Far did it Get...........<br /><br />I'm betting that your Problem is in the Fuel Delivery........<br />Somewhere between the Tank,+ the Carb............

 

[DHPMARINE]

Re: Lots of Backfire!!!!!! why

All above are good and valid points to check.And the problem probably lies there.<br /><br />One thing that seems over looked..<br />Cobra shift problems will shut down 1/2 of the cylinders.<br /><br />so this V8 might only be running on 4<br /><br />DHP