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2006 Mercruiser 496 HO starts then stalls

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2006 Mercruiser 496 HO starts then stalls

Old 10-09-2013, 09:39 PM
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Originally Posted by Sizzle_Technology
I did as you indicated. I swapped the IAC, CAM & Crank sensor, TPS, Clean out the fuel filter, no water in the fuel, swapped the ignition switch. I also took all the parts off the engine that would not run and put all of them on the good engine. All the parts worked fine on the good engine. This tells me that non of those parts were bad.

Today, i contacted the dealer who performed the service. He said the engine was running when he left. The dealer wants me to paid my bill before he sends someone out to look at my boat. I told him he did not fix my boat. Why would I pay him. I told him he is only throwing parts at my engine hoping something sticks.

Does anyone have any other ideas to check?
Thanks, Jeff
dont know that engine real well, but it sounds typical of a bad coil or ignition amplifier.

Had an ignition box that would let me run exactly 12 minutes then quit
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Old 10-09-2013, 09:46 PM
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Originally Posted by lil red
The tech may have done some diagnostics but you don't know which ones, if they were done properly and what the results were. If the boat came to me I would
Check all actual values in the scan tool, tps iac etc
Take a fuel sample
Check fuel pressure
Put a spark tester on a wire and see if it is going out as the motor dies (may or may not be able to catch this.)
Swap ECM
Swap crank sensor
If none of these leads to anything then ohm out all the wires from cam, crank etc to the PCM looking for an open circuit. You can prove out a bad harness vs just replacing it.
If you do these tests and record your findings I'm sure you'll track down your problem faster
Any idea how many a harness costs? How many different hardness does a boat use?
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Old 10-09-2013, 10:07 PM
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Have you taken a fuel sample yet? Checked fuel pressure for yourself? I honestly have no idea what a harness costs but that is the last part I'd replace.
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Old 10-09-2013, 10:16 PM
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Originally Posted by Sizzle_Technology
Any idea how many a harness costs? How many different hardness does a boat use?

Probably a few hundred and a Lot of work to change, lasts resort. Did we find out if we are losing fuel pressure or ignition when it dies I may have missed it, went through the thread quick.If not you need to find out what it losing. I think I already posted
this on your other thread but there is a an oil pressure saftey switch that shuts off the engine if no oil pressue is detected.If switch is bad it would think no oil pressure. Also pull your fuel pump relays and look for and burning/ melting were they plug in.
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Old 10-09-2013, 10:31 PM
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After reading all of this twice and really trying to figure out what has been done or not plus were you are at with this lunch eater to understand everything here. IMO and I have crawled in boats now for 24 years straight plus being most marine OEM trained even currently as of today.

I believe your problem is in your transom harness. Yes the transom harness. There will be 9 sensor circuits for NON DTS ( MECHANICAL ) - This is called 5 Volt sensor circuit mechanical. The layout for this is camshaft position, paddle wheel, oil pressure, sea water pressure, crankshaft position, MAP, TABS, TP and Smart transom. Now either you have a bad connection or corrosion or a wet connection or a short in this 5 V sensor circuit mechanical - the transom harness. Also check all the gray wire sensor leads that come out splice 101 then the output single gray wire input to the PCM connector A pin out 23.

Also for testing always run a motor on a clean remote 3 or 6 gallon fuel tank with fresh gas and a primer bulb inline so you can prime the fuel system and prime extra fuel when your motor is stalling to see if the priming picks the engine back up because of fuel restrictions. This way U can take the boats fuel supply out of the mix and place the problem as engine related. Process of elimination as to were your problems lie. Very simple as that. Spend 30 bucks to help eliminate.

Another thing that's easy to look at and I would not rule this out is your shift switch is bad or way out of adjustment. Good luck.

Last edited by BUP; 10-09-2013 at 11:12 PM.
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Old 10-09-2013, 11:31 PM
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As previously mentioned I would hookup and external fuel source and try running to eliminate the boats fuel supply. When you key the ignition on can you hear the pump prime and build pressure? You may want to try cycling the key on for 5-10 seconds, then off a few times. If the engine runs for a longer period and then stalls you have a fuel supply issue. Have you tried swapping the MAP sensor from the other engine? The engine may be faulting cam and crank sensor codes due to it running / possibly missing for such a short period. A mercruiser scan tool will let you view parameters like Tps / Map / Oil press, etc. All of that is vital to pin pointing the problem.

Alan Gordon
Service Manager
[email protected]
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Old 10-13-2013, 06:11 PM
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OK guys. I got the boat running. After swapping almost every part from the good engine -- IAC, CAM and Crank sensor, ignition switch, fuel filter, PCM, both fuel pumps,fuel rely, testing all connection for 5v connectivity to all connections, I put all the parts from the bad engine on the good engine. The engine started right up. None of the parts were bad. The problem was the fuel pick up from the tank. It was cracked. All it was doing was picking up air. I don't recall which expert -- in this group, thank you very much, suggested that I put a 3 gallon tank between the boats fuel tank and the engine. After opening the fuel pump and filter and pouring some fuel into the compartment, then cycling the engine, the boat started right up.

Here is what I can tell you. Never contact a mechanic to do work on your boat unless you have absolutely no mechanical skills. I never attempted to work on my engines because I was concerned I'd break something. I learned so much by asking all you for assistance. Your recommendations were very valuable. Even though it took me longer to figure out the issue, I know I can do a lot of the work myself now. Trust me, mechanics are very informative. Many of you might even be a service provider. I applaud your your skills. You help me figure this one out. However, the first service provider changed both fuel pumps. As I mentioned before, who knows if there were even broken before. I just received the bill $1243.35. I am waiting for the other service providers bill. They said I needed a new wiring harness, the boat would need to be taken out of the water (Formula 370 SuperSport), the engine would require the exhaust system to be remove, etc...The mechanic worked on the boat for 13 hours. Any guess how much his bill is going to be?

Once again. I thank you all for your help.

Last edited by Sizzle_Technology; 10-13-2013 at 06:13 PM.
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Old 10-13-2013, 09:07 PM
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Congrats on getting things figured out S_T!

I can't tell you how much I have learned by just diving into something and figuring it out. Remember these boats are designed to take a beating; even your SS. They are not too fragile. And if you do break something, well; better off doing so in your slip than out in the ocean.

The internet, both Forums and YouTube/similar are, are two of the best tools you can have in your bag; and they are virtually free.
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Old 10-13-2013, 09:42 PM
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Originally Posted by Sizzle_Technology
OK guys.
Once again. I thank you all for your help.
Bad pickup should have showed in the fuel pressure check. You might be able to fight that first bill. Ask them for proof of good fuel pressure
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Old 10-13-2013, 11:06 PM
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Good for you and what a relief. Post 10 explained it exactly. The basics within an hour would have pin pointed were your problem lies. Basically 3 full sides to eliminate as to where your problems lies for any mechanical problems and or running problems, the fuel supply side, the motor side and the drive / prop side.

Always start with a fuel sample for condition of fuel, always run on a known clean fresh fuel supply, test fuel pressures, read spark plugs, compression test, maybe leak down test after that then of course if its a fuel injected computer controlled motor scan it somewhere in that mix. These are the common basics that any tech should have done right up front.

If the gas tank was filled completely 100 % it is possible that the greatest tech in the world could have missed a broken fuel pick up but once the fuel level started to decrease in the gas tank and the running / starting problems came back, he should have known it was the fuel supply where the problem lies.

Last edited by BUP; 10-13-2013 at 11:08 PM.
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