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Old 03-02-2011, 03:33 PM   #21
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No resolution yet, but a bit of an update.

My son checked a few more things (MAPS sensor, fuel pressure, etc) and all checked out OK, so he's a bit mystified. He'd like to get fault codes from the computer. He has the professional scanner for auto engines, but apparently marine engines use a completely different scanner and connector, and after a few calls no one seems to sell them to the general public. They are expensive anyway, about $2500.

So, I bit the bullet and towed it to a shop yesterday. Briefly discussed what the symptoms are to the mechanic, but he's a man of few words and didn't really want to speculate about the cause. So, I hope to hear something today.

Well, on the positive side, at least the weather is crappy! (so I won't be wishing I could go out on the water)
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Old 03-05-2011, 12:12 AM   #22
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OK here is, I hope, the end of the story. The mechanic checked the fuel pressure, and according to him it was way too high. He saw it spike to 80 psi, and it's supposed to be a steady 43 psi.

The only thing strange about that is my son had checked fuel pressure also and it was about 45 psi for him, so it looked normal.

So the solution was to replace the pressure regulator ... parts and labor were about $200. I can certainly live with that, given what it could have been.

The mechanic noticed the oil was about a quart too high. I noticed that too but didn't connect that to anything. He said it also smelled like fuel, and his theory is that the high fuel pressure caused gas to leak past the rings into the oil. He highly recommended changing the oil, which I agreed to. Just thought I'd mention this in case anyone else runs into this problem in the future.

Anyway his diagnosis is certainly consistent with way too high fuel consumption, black plugs, and white smoke. He even said the oil slick I saw behind the boat could have really been gas mixed with other crud from the engine being blown out the exhaust. I asked him if the computer threw any fault codes, and he said there were none. I'm pretty sure there is no fuel pressure sensor (he thought so too).

So I just brought the boat back today. Don't know when I'll be able to take it out for a test, but I did run the engine in the driveway. No white smoke whatsoever and no surging at idle - all good signs!
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Old 03-05-2011, 01:37 AM   #23
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Thanks for the report back...definitely sounds like you guys got the problem fixed and now your ready for some serious boating....


and...you got off cheaply with only a couple hundred bucks and an oil change.....

SP
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Old 03-06-2011, 10:48 PM   #24
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Quote:
Originally Posted by iceman View Post
....I did run the engine in the driveway. No white smoke whatsoever and no surging at idle - all good signs!
Awesome news Tom, I hope the FPR turns out to be what the problem was. Let us know when you're able to test it on the water.

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Old 03-07-2011, 12:53 AM   #25
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Tom,
Always good to hear when things turn out better than had been feared. Hope your fuel consumption returns to where it should be for the boat. Lord knows it's all gonna cost us more this year. Happy Boating and give us the final report when you get her out again.
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Old 04-24-2011, 07:51 PM   #26
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OK, FINALLY the stars aligned and I got a chance to get out on the water last week. Can't believe the sketchy weather that seems to be persisting this year.

So I made a run up to SF and back, and I'm happy to report the smoking is gone, and the extreme excess fuel consumption is much better. On plane, going about 20 knots, I was registering about 14 to 15 gph versus 20. I thought the norm for that speed, though, was about 12 gph so I may still be a little high. Conditions weren't glassy; there was a small amount of chop and wind, so that would be a factor. I think I need to build up some more datapoints now that I have the floscan dialed in.

Another thing happened while I was out. I was docked (actually stayed in SF for 3 days) and ready to leave, and when I started the engine the RPM oscillated up and down, finally stalling at low RPM. I started it again and it stalled again. Finally after several tries I ran the throttle up a bit, then started it, and it held at about 1000 RPM. I was a little worried that if it stalled out on the water it wouldn't restart, so after warming it up at the dock I stopped and started it at normal throttle, and it started right up. Seems like the cold idle mechanism isn't working right. This is an EFI engine so it's computer controlled, so it's probably a sensor or a controlled valve/flap of some sort. Anyway something else to look into. I'm happy the major problem is solved though!
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Old 04-25-2011, 01:16 PM   #27
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Glad the smoking had abated and that your fuel consumption has decreased Tom.

Regarding the idle issue, from what I've read the most common, and likely, issue is the IAC (Idle Air Control) dumaflingy.

The main throttle blade is closed at idle so the computer uses the IAC to set and control idle. If the IAC is having a bad day the engine won't idle but will run fine otherwise. I don't know if a flakey IAC will throw a code in the computer. I can't remember if the IAC can be cleaned, or if it's just a remove and replace deal.

Dan
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Old 04-26-2011, 03:10 AM   #28
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Dan,
Thanks for the tip about the IAC. My mechanic son told me how to find it on the engine, and suggested I spray some WD40 into it to see if that helps. I'll check it out this weekend and see what happens.

Tom
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