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TOPIC: 5 of 6 cylinders firing

5 of 6 cylinders firing 27 Aug 2017 23:47 #1

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Any and all help would be greatly appreciated! Have a 1998 Bayliner Capri LS 1850 with the 4.3L Mecruiser. Boat starts fine but runs rough. Rebuilt carb then replaced plugs, plugwires, rotor button and distributor cap. Checked fuel from tank, its clean. Did a compression test, 5 of 6 cylinders 140ish one cylinder is 170ish, it is also the cylinder not operating properly. The reason I know this is because I can pull plugwires one at a time and this plugwire makes no difference in idle of engine. Ran boat anyway, ran good for 5 of 6 cylinders. Seemed to loose more power the longer I ran. Started a slight backfire/ slight pop from carb. Pulled plug from said cylinder and it was very nasty with what looked like oil with water in it. Pulled oil stick and it looks like oil was just poured out of can, brand new. Ran again on muffs in driveway no sign of oil in water from discharge, even after drying on concrete no signs of anything. Also no sign of moisture on oil filler cap. Again any and all advise where to look now or what to check next would be greatly appreciated.

I'm leaning toward pulling valve cover to see if there might be an exhaust valve issue. Wondering if this could be a head gasket issue or maybe I'm getting water in this one cylinder from the exhaust manifold?

Thanks, David

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5 of 6 cylinders firing 28 Aug 2017 00:15 #2

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I'm thinking you are getting water into the cylinder mist likely from a leaky exhaust gasket between the manifold and elbow.

Did you clean or install a new spark plug to see if it runs better?

Head gasket or leaky valve would result in low compression.

Do you boat in salt water? How old is the exhaust system?

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1997 Maxum 2400 SCR 5.7LX Bravo II

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5 of 6 cylinders firing 28 Aug 2017 00:44 #3

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Plug was new when trip started, cleaned and re-installed. Cylinder still doesn't fire properly and is getting fire to plug.

The higher compression on that one cylinder, could it be because there is water in cylinder? Haven't turned engine over with plug out. Would it do any damage to actually start engine with that one plug out and see if water blows out of plug hole?

Boat is used in both salt and fresh water. Last use was fresh. Always flush with Salt Away after salt use. I have only had boat 2 seasons and not sure of boats history. Not sure when exhaust was last reworked.

Thanks,
David

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5 of 6 cylinders firing 28 Aug 2017 02:03 #4

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Yes water in the cylinder will show high compression as it's not compressible.

I would remove the elbow/risers and inspect. Post pictures of your findings.

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1997 Maxum 2400 SCR 5.7LX Bravo II

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5 of 6 cylinders firing 28 Aug 2017 02:17 #5

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Nauti Mike wrote: Yes water in the cylinder will show high compression as it's not compressible.

I would remove the elbow/risers and inspect. Post pictures of your findings.


+1 sounds like moisture in that cylinder.
Where ya been Mike, nice to see ya around B)

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www.baylinerownersclub.org/index.php/for...ansom-repair-my-2556

5 of 6 cylinders firing 28 Aug 2017 02:35 #6

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Pull all the plugs pressure test tHe block, you will hear and feel air coming out the plug hole.

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5 of 6 cylinders firing 28 Aug 2017 02:48 #7

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builderdude wrote:

Nauti Mike wrote: Yes water in the cylinder will show high compression as it's not compressible.

I would remove the elbow/risers and inspect. Post pictures of your findings.


+1 sounds like moisture in that cylinder.
Where ya been Mike, nice to see ya around B)


Had to get my head straight after a very long divorce, good to be back.

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5 of 6 cylinders firing 28 Aug 2017 03:08 #8

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Sorry to hear Mike, been there done that :(

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Dave
Edmonds, WA
"THE FIX"
'93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
.030 over-Vortec top end-part closed cooled
***The rebuild of my 2556***
www.baylinerownersclub.org/index.php/for...ansom-repair-my-2556
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