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2008 6.2 died suddently

T

tugwood

New member
Took our 2008 boat with Mercruiser 377 out for the first time this year after starting and running it for 20 minutes in the drive. In the water it ran like a champ for over an hour. After cruising at idle speed for about 10 minutes at one point I applied throttle and it coughed, sputtered and died within about 5 - 10 seconds. It would not restart. Cold in the driveway would not start. Checked fuel filter,, perfect, checked fuel pressure, 45psi at rail. checked relays, kill switch fine, check crank position sensor, checked three main relays. took a plug out to check for spark and my helper said it looked alright. About to give up and take it in when I thought I would just try one more time taking a plug out to check for fuel vapor. I had an alternate plug out from the first time and after turning over just a few times the engine started..... just like nothing was wrong. Did not know what to think so replaced the plug and wire to number 6 and tried restarting,,,, nothing, dead again. Took the wire off number 6 and it started right quick again, could hardly tell it was missing a cylinder. Assumed it was the plug so swapped that with another. Still would not start without # 6 wire off the plug or out of the distributor,, disconnecting at the distributor or the plug had the same effect. Took the distributor off and found nothing suspicious there. No 6 at the distributor is adjacent to the coil inlet I noticed. Is it possible there is an internal leak in the distributor between the coil path and # 6? I measured resistance with normal meter and found nothing. I am going to use a meggar tester later today. Has anyone ever heard of an issue like this before? It is not comforting to think that one bad plug or wire or one cylinder could and did leave me stranded out in the water. I am very lucky we were not far from shore and as luck would have it a public boat launch. Often I am miles off shore in Lake Ontario.
 
Firing order check this out 1-8-4-3-6-5-7-2 clockwise. Cylinders Front Rt. Side 1-3-5-7, Front Lft side 2-4-6-8.

By the way, #6 is the alternate, & opposing cylinder to #1. Both pistons are at TDC at the same time, only one is on the compression stroke, (firing) while the other is on the exhaust stroke.(not firing). This seems like you have more then a coincidence if you're having issues with #6? I've seen these engines run smooth (with no indication) of crossed plug wires, but lacking full power.
 
Via your specific engine model number, look at Merc's ignition trouble-shooting section. Perhaps try to recreate the issue and pull codes.

If you have a certified Merc shop do this for you, ask for and be willing to pay for proper diagnostics up front.
Only upon recieving full diagnostics that clearly define the problem, and only upon recieving a written "quote" (not an estimate) stating that the work scope will indeed correct the problem, move forward.

There's no reason to pay for work scope that does not correct the problem.

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Mik, I don't necessarily disagree with you.... but let's make this as goof-proof as possible for the OP.

MikDee said:
Firing order check this out 1-8-4-3-6-5-7-2 clockwise.
Assuming that this is an I/O..... Cylinders Front Port Side 1-3-5-7, Front Stbd side 2-4-6-8.

By the way, #6 is the alternate, & opposing cylinder to #1. Both pistons are at TDC at the same time, only one is on the compression stroke, (firing) while the other is on the exhaust stroke.(not firing).
Although unrelated to his issue..... no two pistons are at TDC simultaneously, regardless of the stroke.
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Just a WEG (wild eyed guess) maybe Cyl #6 is on it's exhaust stroke, or the valves are open creating no compression at the time, meaning No fire!
 
tugwood said:
Our 2008 boat with Mercruiser 377 Is it possible there is an internal leak in the distributor between the coil path and # 6? Has anyone ever heard of an issue like this before? It is not comforting to think that one bad plug or wire or one cylinder could and did leave me stranded out in the water.
Click to expand...
Nice job diagnosing it. If you Google search "Mercruiser flat cap problems", you will find many similar stories like yours. A new cap and rotor (that was manufactured after 2013 for your safety) should solve your problem. Good luck.:) https://www.google.com/search?q=Mer...s&rls=com.microsoft:en-US:MIE-Address&spell=1
 
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Hi, after doing a little research, a little procrastination and lots of other things I have good news... The engine started right up after purchasing a new cap and rotor from Mercruiser. Some people at another forum suggest using a high grade after market automotive cap and rotor which was cheaper than Merc's and tempting however if that did not work I knew I would be left wondering if it was the new cap. Megger testing the old cap like I talked about did not show any problems FYI. I am left wondering exactly what the problem was since cap and rotor were changed at the same time and even if it was the cap I would still like to know what went wrong with it. Always good to know exactly what the root cause of a failure is to prevent a repeat.
Thank you for contributing your advice boat tech. You were right on the money. For Chris the boat does not have smart craft gauges. It is an 08 Cobalt 222. I am not a pleasure craft expert or a gas engine technician but am a marine engineer most familiar with commercial large bore diesel engine driven ships. It helps!
 
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