Reply With QuoteWhere did you get the gas? How old was it?
What would cause detonation within a HP500EFI? Mercury is stating bad fuel!!! I say BS.
Here's the deal. I was running down from Topock at approx 4800 rpm. I smelt buring oil and shut the starboard motor down after opening the hatch the starboard motor had smoke coming out of the flame arrestor, we thought it was blow back. Checked the plugs, two oil fouled plugs, one lean plug on the port side of the starboard motor. Compression test, two cylinders pushing 0, one 25, all others 145 to 150. Pulled the head, cracked piston on number 7, blew a hole between 5 & 7 on both the head and on the surface of the block. Gasket is burned and destroyed. Intake and exhaust valves look good at this point, no bends or defects showing. Pulled the head on the other side, everything is fine. The port motor is also okay.
What can cause detonation? How can I protect myself from this again? Im under the impression that detonation is caused by a lean condition, timing, etc.
Does anyone know of a place where I can have my fuel tested, if its not the fuel then im thinking maybe my ECU is bad, and casued a lean condition. Has anyone had a similar problem with a HP500EFI and what was the outcome.
Last Question - How the hell do you know what the cause of the problem actually was so you can avoid it in the future? All they can tell me is a had a faliure due to detonation. Something caused the detonation!!! So WTF!!!
3DO
Where did you get the gas? How old was it?
sounds like pre-ignition detonation. Thats bad news.
That should not have happened in that motor. Compression is too low.
Maybe it could have leaned out. Can you find that out?
3DO. Sorry to hear about your motor. You might want to bench test the fuel injectors. Perhaps some of them are failing, which caused a lean condition.
check everything make sure the injector is good (ohms) also some shops in your area may have an injector bench tester to use the injector on the bench and check them when hot.
check timing and also see if your dealer has any updated programs for your pcm. check the fuel pump and filter. pressure and see if you can fing a flow rate for the pump in gph then see how much flow you have.
when you get it back together see if you can go to the dealer and have them hook up the scan tool and see where it is in the fuel map at idle and 2500 rpm. check for vac leaks and timing while runing
If you had detonation from bad gas or over-advanced ignition timing I would think that you would have had a major melt-down with all of the cylinders. The fact that only three cylinders show any problems does not look like detonation.
The first thing to go in a detonating engine is the spark plug electrodes and ground straps. Detonation will also melt the top of the piston and destroy the top ring land. A crack in the piston doesn't sound like detonation to me.
The knock sensor should have sensed detonation and retarded the timing until it went away.
A blown head gasket usually comes from overheating the engine (and distorting the block to head mating surface). The alarm should have gone off.
You should bring the boat to another dealer for a second opinion about the engine.
Dennis Moore
All of this info is great, I can use all the help I can get. I will talk to the Merc rep about all of it monday morning. Im thinking, but not sure if this is possiable. It blew a head gasket between 5/7 and while running the motor was getting flame back and forth from 5 to 7 acting as a torch and burning the hole in the block and head. Finally after the hole got big enough the compression from number 5 blows into 7 causing pre-detonation cracking the piston. Does this sound like a possiablity or am I way off key. Im not a motor guy in anyway, but im going to be learning much more now. Thanks for any advise that is given, and I will take all of it to heart while fixing this problem, and avoiding the same problem later. I will have the fuel injectors tested on tuesday. If my guy does not have a way to test them do any of you know where I can send them out too?
HH
50 gal. per side at Texaco and another 25 per side at Arco - 150 total between the two. (Probably a mistake, Im hearing Arco gas is the worst, to late and after the fact) The head, valves, head gasket, plugs, and piston where fine on the port side of the bad motor. That kind of says to me that it was not a bad fuel issue. Im still leaning more towards. Fuel Flow to the three bad cyclinders, ECU screw up, or blown head gasket.
3DO
this could be related in a way: i had a loose ground connection from the motor to battery once. it cuased the knock censor to fail in the ecu. it was replaced immidiatly though becuase the alarm still caught it. just a thought . good luck with it
I would have thought that the knock sensor would have picked it up also. Sounds more like a mechanical failure too me!
I sure hope it is under warranty
Originally posted by Three Days Only
50 gal. per side at Texaco and another 25 per side at Arco - 150 total between the two. (Probably a mistake, Im hearing Arco gas is the worst, to late and after the fact) The head, valves, head gasket, plugs, and piston where fine on the port side of the bad motor. That kind of says to me that it was not a bad fuel issue. Im still leaning more towards. Fuel Flow to the three bad cyclinders, ECU screw up, or blown head gasket.
Well, I know you may find this hard to believe, but I agree.
It seems like the first cry is always "bad gas"...probably because that's one of the few "operator errors" that they can point to.
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