White smoke coming out of carb and 454 is hard to start

[cxw]

We have a 1986 Chris Craft 381 Catalina with dual merc454 engines. The starboard engine was rebuilt completely last summer after throwing a rod. The rebuilt engine is now hard to start, sometimes impossible, and when you try to start it the engine will cough a few times and then "belch" white smoke out the spark arrestor. I changed out the fuel filter. The gas in the filter was muddy brown. After changing the filter there was no difference in what was happening. Removed the filter and the gasoline in it was clear and there was no evidence of water, etc.. in the fuel. No problems are happening with the older port engine. Any suggestions as to what would be causing the problem?

 

[RogersJetboat454]

Re: White smoke coming out of carb and 454 is hard to start

Welcome to Iboats.

Have you checked the ignition timing? Overly advanced timing will make the engine difficult to start, and will occasionally cause backfires out the carb.

 

[cxw]

Re: White smoke coming out of carb and 454 is hard to start

Welcome to Iboats.

Have you checked the ignition timing? Overly advanced timing will make the engine difficult to start, and will occasionally cause backfires out the carb.

We haven't yet but will today. Thanks for your reply.

 

[wrench 3]

Re: White smoke coming out of carb and 454 is hard to start

I'm with Rodger. The distributor could have come loose and rotated on you. You could also check the inside of the distributor cap for moisture or carbon tracking.

 

[Don S]

Re: White smoke coming out of carb and 454 is hard to start

The gas in the filter was muddy brown. After changing the filter there was no difference in what was happening.

Along with the timing, that muddy brown what ever it was in the filter may have bypassed the filter if there was enough in it and now be in the carb. Replacing the filter will not clean out the carb.

 

[Bondo]

Re: White smoke coming out of carb and 454 is hard to start

Along with the timing, that muddy brown what ever it was in the filter may have bypassed the filter if there was enough in it and now be in the carb. Replacing the filter will not clean out the carb.

Ayuh,.... Agreed,...

That muddy brown what ever it was in the filter may have been responsible for the original failure....

 

[wrench 3]

Re: White smoke coming out of carb and 454 is hard to start

From my experiences a plugged up carburetor will cause a backfire under load, but not when starting. Water in the fuel will give you a crank and no start, but no backfire.
The brown stuff does make me wonder if you've checked the fuel water separator on the other engine?

 

[ENSIGN]

Re: White smoke coming out of carb and 454 is hard to start

I think you'll find that brown stuff in the carb.It's probably time to check the contents of the tank.

 

[vintage2]

Re: White smoke coming out of carb and 454 is hard to start

White smoke from an engine usually means water. Could be left over in the carb, but I get the feeling you should do a compression and/or cylinder leakdown tests. Also if you have a closed cooling system you can try a pressure test (Borrow the tools from Advance or Autozone). I suspect a leaking head gasket. How does it run after it starts? I have a 454 in my '89 Sportcraft w/closed cooling and even when I had water in fuel on one occassion it cleared up after filter change and running 30 minutes. Good luck.

 

[mikeav85]

Re: White smoke coming out of carb and 454 is hard to start

I'm going through the the same thing with my 1990 aariva 2450 with merc 454. just had the engine rebuilt and it has new starter, fuel pump, fuel lines, spark plugs, plug wires, cap and rotor, manifolds, risers....and now the thing won't start. I'm having the same problem with the engine struggling to start and then as soon as i give up and let go of the key it back fires and shoots out white smoke from the flame arrestor. i took it in to the local shop this weekend and they say that the engine if fine but that i have a problem with the ignition system. they gave me two options; change things out one at a time or just replace the entire ignition system with an MSD system, distributor, coil, and control module. I'm not sure if they just want to sell some stuff or if they are just stumped. PM me and i'll keep you updated on whatever i find out with my boat. my next step before i spend anymore money is to go through the entire ignition system and make sure that there isn't a loose or disconnected wire somewhere that is keeping me from getting spark. hope you get your boat running.

 

[cxw]

Re: White smoke coming out of carb and 454 is hard to start

I'm going through the the same thing with my 1990 aariva 2450 with merc 454. just had the engine rebuilt and it has new starter, fuel pump, fuel lines, spark plugs, plug wires, cap and rotor, manifolds, risers....and now the thing won't start. I'm having the same problem with the engine struggling to start and then as soon as i give up and let go of the key it back fires and shoots out white smoke from the flame arrestor. i took it in to the local shop this weekend and they say that the engine if fine but that i have a problem with the ignition system. they gave me two options; change things out one at a time or just replace the entire ignition system with an MSD system, distributor, coil, and control module. I'm not sure if they just want to sell some stuff or if they are just stumped. PM me and i'll keep you updated on whatever i find out with my boat. my next step before i spend anymore money is to go through the entire ignition system and make sure that there isn't a loose or disconnected wire somewhere that is keeping me from getting spark. hope you get your boat running.

I will keep you in the loop on what I find out on my boat. At this point the #1 target to check is the distributor cap and then the spark plugs. I will then follow up with checking the engine compression. I will keep you posted. Thanks for your input.

 

[wrench 3]

Re: White smoke coming out of carb and 454 is hard to start

I'm going through the the same thing with my 1990 aariva 2450 with merc 454. just had the engine rebuilt and it has new starter, fuel pump, fuel lines, spark plugs, plug wires, cap and rotor, manifolds, risers....and now the thing won't start.

If it hasn't started since the rebuild, it may be worth checking the valve timing. This can be done with only removing one rocker cover.
Also remember that the ignition timing could appear to be correct but the distributor could still be off by half a turn. This could be checked against the valve timing, or when #1 cyl. gets compression.

 

[Don S]

Re: White smoke coming out of carb and 454 is hard to start

Do a compression test. That alone will answer a LOT of questions.