Mercruiser 3.0 won't start, turns over, fire/smoke in carb

[wticer]

2003 Mercruiser 3.0 will not start. Engine turns over, but when fuel goes into carb, the engine slows or bogs and there is a quiet sounding backfire through carb. When I removed flame arrestor and tried to start, the result was a brief flame/fire in the carb. Could this be caused by a stuck valve? Any other suggestions? This boat sat for about a year without being started.
So far I have bought new coil, plugs, distributor cap, rotor, carb, fuel line, battery, fuel removed and new fuel added.
Any help would be appreciated.

 

[cjf2848]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

Make sure your spark plug wires are in right order on the distributor cap. Mine got mixed up during a timing issue and come to find out, that was prob. #2 and 3 were switched

 

[wticer]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

Thank you. I should have included that I do have plug wires correct.

 

[atomb]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

New carb? you need spark , compression and fuel. Hows the spark and the compression? I would check those first and then move fuel. download the manual and follow the diagnostics abit. Has the carb been sitting a year?

 

[Brewman61]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

This may be a long shot, but I once rebuilt a carb on a car, and when I put it back on, I got flames and backfiring. Turned out to be a bad gasket between the carb and the intake manifold, causing a vacuum leak.
Put on a different gasket set, and it solved the problem.

 

[wticer]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

Tested spark with light and good on all 4.
Compression on 1 is 120, while compression on 2-4 is 175. obviously I couldn't warm up the engine prior to the test.
Carb is new, but the problem was exactly the same before I changed. Yes, getting fuel spray into carb.
Would the compression numbers really cause this? If so, any suggestions?

 

[airdvr1227]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

Timing?

 

[fishinpa]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

2003 Mercruiser 3.0 will not start. Engine turns over, but when fuel goes into carb, the engine slows or bogs and there is a quiet sounding backfire through carb. When I removed flame arrestor and tried to start, the result was a brief flame/fire in the carb. Could this be caused by a stuck valve? Any other suggestions? This boat sat for about a year without being started.
So far I have bought new coil, plugs, distributor cap, rotor, carb, fuel line, battery, fuel removed and new fuel added.
Any help would be appreciated.

Does this engine have points /
Are you absolutely sure that All plug wires are in the correct position and you are following around the dist cap in the correct rotation??

fish

 

[wticer]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

Good question. I sure was absolutely certain. Until I put the compression tester on and saw the rotor 90 degrees off from where it should be at each cylinder. I'll take the hit for being an idiot, but the diagram in the manual and everywhere else I could find shows number 1 at 1 o'clock as you look at it from the side. Turns out that is number 2 (at least on mine). I had not started the boat since I got it back on a repo type deal so I'm not sure how the plug wires got switched. Thank you to those who replied. I am posting a picture of it the correct way -- number 1 at 5 o'clock and on to 3-4-2 from there, clockwise. Hoping that helps the next guy. BTW, compression leveled out after running for a little while. Now all four are between 150-155.

 

[SSTKO81]

Re: Mercruiser 3.0 won't start, turns over, fire/smoke in carb

Is this true of all years of the 3.0/181? I've got an '81 and I just cant get it to start. I have spark to the 3 & 4 cylinder, but not 1 & 2. I thought number one was at 1 o'clock too and now I'm seriously doubting my marine mechanic abilities. This could deffinately be a big part of the problem.