575SCi rich idle issue
 

I just did a bunch of research on some other posts with very similar problems to what mine did yesterday. So, I have some ideas, but due to the weather variable, I thought I'd get some of your opinions.

The powerplant is a 2003 575Sci with a 3in blower pulley, Superchiller, and raw water moved to under the bilge with a Hardin marine sea strainer. Top end re-done by PO @ 300 hours. said everything was done, my surveyor knew the mechanic who did the work and he confirmed that.

So now the story. it ran great all weekend. And all weekend it probably didn't go below 65 degrees (even at night). During the day it got to about 88, and when we put it in the slip Saturday night, it was probably still 75 degrees.

Now, Sunday morning, 30 degree temp drop. It was probably about 58 degrees or so by the time we got going. It started fine. But when we got out of the no wake, it sure took at least a minute of part throttle, and quite a bit of black smoke before it finally woke up. I didn't think anything of it as I have read these things are cold blooded. Then it seemed fine. That sum***** just ran! It pulled hard, would go to WOT beautifully, and cruise ad mid-throttle great. BUT then - every time I'd go down to real low throttle/idle it would do the same thing - black smoke, and take 15 seconds or so before it would snap out of it at mid-throttle. AND any time you try to idle for more than 10-15 seconds you could just hear the cylinder drop out as it fouled plugs.

So, the water temp probably didn't change much, but the air temp did...but it wasn't insanely cold.

So now I'm at a bit of a sense of confusion. Did the MAP sensor go bad and the weather is just coincidence? Or, did the weather play that big of a part and I either need to A. get that valve someone mentioned to the superchiller that doesn't allow flow at idle OR verify the ECU has been re-mapped (that's the one part I'm unsure of.)

Sorry for the long post!

Thank you.

Here is a good link but not necessarily your particular fix. Just wanted fo forward it on although you may have seen it. Amazing how finicky these can be. A quick rule out could be t-stat and or t-stat sensor. Regardless hope this helps you out.

http://www.offshoreonly.com/forums/g...i-experts.html

I have a 575 and the stock tuning at idle sucks, very rich. If your chiller is plumbed with water running though it at idle it will also load up after just a short period. The combination of the 2 is a double whammy.

I sent my ecm out and had remapped, I am not a huge fan of canned tunes but I copied someone with the same setup as mine.

I didn't catch whether you just got the boat and just become aware of this or if you've had the boat and didn't have any issues until recent?

The stock tune does suck, the'll smoke, won't idle down, randomly sneeze and die after throttle is applied coming off idle, all at random,,,,after I had the ECM's reflashed after engine mods, all of those bad habits were gone

Sounds like you have the teague chiller kit, I believe there is a fuel pressure increase with that kit which will also make the stock idle even more rich. There is also the possibility that the idle is enriched due to the cold temps.

I was thinking.

Over labor day weekend, on Saturday, it rained and got fairly cool AND the water temp was pretty cool. I would say the conditions were very similar to the day where my issue happened. (although air temp may still have been a little cooler they day of the issue.)

Anyway, I did not have a problem on that Saturday. And, this past weekend, when I opened the engine hatch to begin winterizing it sure smelled gassy. And the hose that runs up from fuel pump and into the flame arrestor seemed kind of filmy.

Has anyone ever failed a fuel pump on one of these? And fuel overflows and actually comes up that hose and into the flame arrestor?

Is there a way to test the pump off the boat?

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that’s not uncommon, There’s a plug on the sea pump housing( for gear lube level check) take that out and I’ll bet you have a bunch of gas home out of it