Mercruiser 496 proplem
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JohanSweden (12-22-2020)
#12
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Thank you all for the advices, when im thinking of it.. I may have seen it arcing somewhere on the engine one time last year when it was darker in the engine compartment.
Definitly gonna check the spark plugs..!
What resistance should the wires have?
No beeping alarm from the engine.
Definitly gonna check the spark plugs..!
What resistance should the wires have?
No beeping alarm from the engine.
#13
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I wouldn't recommend that you are standing in the engine compartment, standing in the water mist, with shorts(bare skin) when you find a bad wire. I know a tech that had this happen and now he doesn't mist test, just recommends a new wire set every 2-3 years. He had to have sprayed a lot of mist expecting nothing but to this day if he gets a bit cocky, someone in the group will ask how to test a wire set on the engine - LOL
#14
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2-3 years ? Really ? All the more reason to reduce gaps to a more normal .045 on these app’s with coil and wire burning ridiculous .060” gaps.
#15
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I started with measure the spark plug cables.
With my multimeter at 20K I got these numbers, starting on port side and from the front of the engine.
Port side
1 - 2.37
2 - 3.04
3 - 3.03
4 - 2.37
Starboard side
1 - 2.38
2 - 3.06
3 - 3.01
4 - 2.35
With my multimeter at 20K I got these numbers, starting on port side and from the front of the engine.
Port side
1 - 2.37
2 - 3.04
3 - 3.03
4 - 2.37
Starboard side
1 - 2.38
2 - 3.06
3 - 3.01
4 - 2.35
#16
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Dont know if the resistance is good or bad.
If the resistance is good, can it still be some fault in the spark plug cables?
Or is it one of the eight ignition coils that can cause the problem?
If the resistance is good, can it still be some fault in the spark plug cables?
Or is it one of the eight ignition coils that can cause the problem?
#17
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#18
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Hello
But I still have some small issues with the engine RPM. The engine runs porely between 800-1500 rpm when I give the engine a little bit of gas (when not on plane), just cruising around.
It sounds like one cylinder is missfiring or something. But when im running the boat on plane/full gas its fine, no problems..
What can cause this to happen? Bad spark plug wirings?
I run the OEM Aldelco spark plugs.
Thanks for help where to start searching
But I still have some small issues with the engine RPM. The engine runs porely between 800-1500 rpm when I give the engine a little bit of gas (when not on plane), just cruising around.
It sounds like one cylinder is missfiring or something. But when im running the boat on plane/full gas its fine, no problems..
What can cause this to happen? Bad spark plug wirings?
I run the OEM Aldelco spark plugs.
Thanks for help where to start searching
#19
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#20
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Here is some pictures of all the spark plugs in order. Starting from the back of engine.
Starboard plugs at the left, port plugs at the right.
Back of engine
8 7
6 5
4 3
2 1
Front of engine
In my eyes there is several plugs that dont look good, but the first spark plug on port side (#7 cylinder?) dont look good at all... almost completely black...
what do you guys think?
Also, when I turned the engine by hand to look at the valves opening and closing, the exhaust valve at cylinder #5 doesnt close all the way.
It first didnt move at all. But when I turned the engine a couple of turns it started to move and close (but didnt close all the way)...
![](https://cimg2.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/1080x1920/a0c6b896_5622_4dd2_9916_5081cb72c3f2_cb88cb49d8bddc71c1b2f57079a833c08152b73f.jpeg)
![](https://cimg3.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/1080x1920/041b3560_8643_4ca2_bde5_385a6c809224_1d944f53dbafc6e86c4be3c9d2118a7675d8e3ef.jpeg)
![](https://cimg4.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/1080x1920/86c933b7_bea5_4b1a_a7f7_089a036b03bd_793b2e036e412b325be3733273a38d32b6e4a532.jpeg)
Starboard plugs at the left, port plugs at the right.
Back of engine
8 7
6 5
4 3
2 1
Front of engine
In my eyes there is several plugs that dont look good, but the first spark plug on port side (#7 cylinder?) dont look good at all... almost completely black...
what do you guys think?
Also, when I turned the engine by hand to look at the valves opening and closing, the exhaust valve at cylinder #5 doesnt close all the way.
It first didnt move at all. But when I turned the engine a couple of turns it started to move and close (but didnt close all the way)...
![](https://cimg2.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/1080x1920/a0c6b896_5622_4dd2_9916_5081cb72c3f2_cb88cb49d8bddc71c1b2f57079a833c08152b73f.jpeg)
![](https://cimg3.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/1080x1920/041b3560_8643_4ca2_bde5_385a6c809224_1d944f53dbafc6e86c4be3c9d2118a7675d8e3ef.jpeg)
![](https://cimg4.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/1080x1920/86c933b7_bea5_4b1a_a7f7_089a036b03bd_793b2e036e412b325be3733273a38d32b6e4a532.jpeg)