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Old 04-12-2016, 08:22 AM   #21
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I had this issue on our 330 Cummins (mechanical injectors) a few years ago. Turned out to be one failed injector. Next time you start, check the exhaust flange temperature of each cylinder as the engine warms up. Any cylinder lagging behind in temp rise ........ check it's injector. Watched the Cummins tech use this technique on our boat; now an optical pyrometer and spare injector are always on board.
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Old 04-12-2016, 11:00 AM   #22
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The pre qsb 6bta really struggles to be environmentally friendly. It has these electric heaters that heat the air after it goes through the intercooler when the engine is cold. I have to idle out of my marina for a long time and the engine doesnt warm up until i can get the engine up to 1200 rpm or so. Meanwhile, during low rpm, these air heaters are going on and off and my voltage goes down to 9v when the heater is on, then pops back up to 14 when it is off. On for 5 secs or so, then off for 5 secs or so. We measured the temperature of the alternator during one of these runs through the harbor and it was like 3000 degrees. Needless to say, I disconnected the air heaters. A friend of mine with the same engine has his air heaters on a switch, but i dont know why. He says he never turns the heaters on. Anyhow, I think the air heaters were meant to cut down on the unburned fuel coming out of the exhaust.
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Old 04-12-2016, 11:11 AM   #23
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I'd agree with all the comments so far that it is pretty normal for the 6bta to have a slight fuel sheen out the exhaust on start up but it also might be worth having a look at you fuel coolers. When they get older they can leek into the cooling raw water. The fix is either replace them to get rid of them with a kit from Seaboard Marine,

Brett
While this is technically possible, it is more likely that seawater finds its way into your fuel system than the other way around. Ask me how I know....:banged:
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Old 04-12-2016, 11:14 AM   #24
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The pre qsb 6bta really struggles to be environmentally friendly. It has these electric heaters that heat the air after it goes through the intercooler when the engine is cold. I have to idle out of my marina for a long time and the engine doesnt warm up until i can get the engine up to 1200 rpm or so. Meanwhile, during low rpm, these air heaters are going on and off and my voltage goes down to 9v when the heater is on, then pops back up to 14 when it is off. On for 5 secs or so, then off for 5 secs or so. We measured the temperature of the alternator during one of these runs through the harbor and it was like 3000 degrees. Needless to say, I disconnected the air heaters. A friend of mine with the same engine has his air heaters on a switch, but i dont know why. He says he never turns the heaters on. Anyhow, I think the air heaters were meant to cut down on the unburned fuel coming out of the exhaust.
My heaters are still hooked up. With the engines off and using these heaters like a preheater, the voltage drop is about half of a volt...without the assistance of an alternator. So your batteries must have been near death if that is how it happened. I have never seen so much as a twitch with the engines running. But yes, the engines do take a while to heat up...and I don't think it has anything to do with these heaters....
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Old 04-12-2016, 11:21 AM   #25
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The heater will suck a LOT of amps and will shorten the life of your alternator precipitously. It's not needed for marine use, they start fine without (my Cummins has no heaters) but you must warm up with a load. Start and leave the dock right away and no "winter warming" not in gear.
Baker, your description of how your heaters work is opposite to how my friends with Cummins heaters work. I think yours are malfunctioning and that's a good thing.
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Old 04-12-2016, 12:05 PM   #26
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I kept the air heater on my 450 Cummins, but put a switch on the helm. It does help on winter starts where engine is like 40F. Not needed for starting there, but it does reduce the smoke til it is warmed up.

99% of the time the air heater is left off to avoid punishing the alternator.
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Old 04-12-2016, 01:59 PM   #27
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My heaters are still hooked up. With the engines off and using these heaters like a preheater, the voltage drop is about half of a volt...without the assistance of an alternator. So your batteries must have been near death if that is how it happened. I have never seen so much as a twitch with the engines running. But yes, the engines do take a while to heat up...and I don't think it has anything to do with these heaters....
The start battery is new and in good condition. My mechanic told me he disconnects most of these heaters in these engines since it puts such a huge load on the alternator. He also told says most of the preheaters that are this age have failed by now to begin with. Maybe you have a bigger alternator than i do or your preheaters aren't working. This is a known issue with the pre-2000 6bta and is well understood by most NT owners.
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