Help! Mercruiser 3.0L Backfiring - No Power - Stalls

[andrewsilver]

Help needed before Labor Day weekend - please!<br /><br />My 1990 Mercruise 3.0L Alpha One backfired while running last weekend. It ran rough, so we let it cool down, started up and everything was fine.<br /><br />This weekend, I could barely get it started. When I did, it ran fine below 1500rpm idle getting out of the marina.<br /><br />Then I opened up the throttle, it backfired, ran rough, and eventually stalled. I hobbled back to the marina.<br /><br />Other posts have said water in the gas, water in the carb, or timing is off. I've never changed the fuel filter and can't find it on the engine - if someone knows could you please point me to it, thx.<br /><br />One guy told me he had the same problem - his carb was loose and air was leaking in. He tightened the bolts and screws and problem was gone. So I did the same - tightened everything. Problem still there. I cleaned the flame arrestor, changed the spark plugs, adjusted the mixture at idle - but problem is still there.<br /><br />Any help greatly appreciated - Labor Day Weekend is coming up and I'm dying to take the boat out.<br /><br />Thanks,<br />Andrew

 

[Bob_VT]

Re: Help! Mercruiser 3.0L Backfiring - No Power - Stalls

The fuel filter is more than likely intergrated into the carb. It appears like a bushing that the fuel line goes into..... but that may not be the problem (it is cheap to change though).<br /><br />Check for water in the fuel. Check that the float bowl on the carb is clean and the float has not developed a hole in it. Also check your accelarater pump they are popular for going bad.<br /><br />Check your distributor cap for cracks, check that the distributor is tight and has not turned.<br /><br />Bob

 

[andrewsilver]

Re: Help! Mercruiser 3.0L Backfiring - No Power - Stalls

Found the fuel filter, thanks. I don't think that's the problem though. Distributor cap has no cracks, and I checked all the wires. I'm going to have to have the timing checked since I don't have a timing light anymore.<br /><br />If there's water in the tank (I don't know how it got there...) - how do I empty it? I just filled the tank <br /><br />Any other thoughts or ideas, thx.<br />Andrew

 

[ed_hall1]

Re: Help! Mercruiser 3.0L Backfiring - No Power - Stalls

Try pouring HEAT (or similar) into the gas tank. It removes water form the gas during the winter to prevent gas line freeze-up. I would use one can (approximately 10oz) per 5 gallons. This will only work if limited amount of water in gas tank. <br /><br />If still not the problem try spraying carb cleaner on the outside of the carb near the carb/intake manifold gasket. Do this while the engine is running, and be sure to hit all possible angles. If the engine surges or runs worse, there is an air leak at the intake manifold. Had a similar problem with my 88 Stingray. Replaced the carb gasket and now purrs like a kitten. Good luck....

 

[dhammann]

Re: Help! Mercruiser 3.0L Backfiring - No Power - Stalls

sounds like a fuel problem. Could be the passages in the carb are stopped up with varnished fuel. Take the carb off (very easy on this engine) and remove the top half of the carb and examine the bowl. if it is cruddy looking chances are good that things are plugged. Use fine wire and carb cleaner on all the drilled passages and blow out with compressed air. Back firing is ususlly caused by improper fuel vaporization which causes a lean and rich swing.

 

[denniz]

Re: Help! Mercruiser 3.0L Backfiring - No Power - Stalls

Ususally lean, check your power valve below the two jets and make sure its clean

 

[andrewsilver]

Re: Help! Mercruiser 3.0L Backfiring - No Power - Stalls

Thanks for the pointers. Since we're towing the boat 6 hours for a hopefully relaxing Labor Day Weekend, I decided to give in and take it to the marine center. I never do this... but I don't have the time between now and Friday to fix it myself - so I gotta pay...<br /><br />Well, they just called with the diagnosis: Said it needs to have the carb rebuilt: $240 labor + parts! I'm a bit shocked.<br /><br />Does it really take 4 hours to rebuild a carb? I thought it just means to remove it from the manifold, then replace the gaskets, screws, screens and jets, and re-install?<br /><br />I've done that on my snowmobile carb in 15 minutes. I'm obviously missing something here - please educate me, thx.