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Topic Title: Engine Coughs under load?
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Created On: 05/24/2012 09:13:10 AM
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 05/24/2012 09:13:10 AM
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Patriyacht
Junior Member

Posts: 6
Joined: 06/19/2009

Hi,
I've been getting lots of valuable info from the experts here for a couple years already. I hope to be able to give some advice someday.

I have a 43' Nauti 1972 with twin ford 302's. I had a bad bout with water in my gas and I thought I had it whipped, but no. The engines run fine at idle and all the way up the RPMs in neutral, but as soon as I put her in gear they sputter and cough out the carbs, like a backfire. I had both carbs rebuilt, and new dist caps, rotors, plugs and wires. It's got all the regular Mechanics at the marina scratching their heads.

I'm in Afghanistan for a couple more months so I'm just trying to get an idea of what to dig into when I get home.

Any help would be wonderful.

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'72' Nautiline 43' Hole in the water
 05/26/2012 01:32:11 PM
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FranticallyRelaxing
Admiral

Posts: 370
Joined: 09/10/2006

if both engines have been repaired and both engines have exactly the same running problem, the only common denominator is the gasoline, or its delivery.

I had a similar problem recently, where my starboard engine run fine until I needed it to push the boat. The problem turned out to be a hole in a shared fuel line on the draw side- it didn't leak, but it allowed air to be sucked in while the SB engine was trying to pull fuel thru it. Kind of like if you put a hole in your drink straw above the drink, you'll get some liquid, but mostly air.

This may be your problem-- could be say, a pinhole or crack in the draw tube in the tank, or maybe the line right at the top of the tank next to a fitting. (my line was cracked next to a fitting, I found it by accident). You could be drawing enough fuel to keep it idling or doing short bursts, but not enough to feed it under any load.

If possible, bring aboard a separate fuel container, equipped in such a way that you can feed both engines from it, and see if the new fuel supply makes a difference. If it does, then you need to determine if your sucking air, or bad gas...

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1988 SkipperLiner 53x14
1995 Tracker Party Cruiser 32 *for sale*
2003 Chaparral 260 SSI
2000 Allegro Bus 40' DP
 05/27/2012 08:14:49 PM
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LongJohn
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Posts: 123
Joined: 11/13/2004

FranticallyRelaxing assumes that you have a common fuel tank. If true, he suggests an excellent line of inquiry. In 1972, electronic ignition was not widespread in boats. If you're using a points/condenser ignition, try replacing the condensers. Age will cause them to decay and engine performance will be similar to what you've described.

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Harbor Master 47
Watts Bar Lake - TN River
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