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  #26   IP: 172.56.22.9
Old 11-01-2018, 08:22 PM
jayw jayw is offline
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Unhappy

This is a great example of why not to ignore noises in the engine: doing so makes for very expensive repairs.
Engine started knocking on last 4 hour trip of season to bring boat to haul-out in Plymouth- didn't have much choice but to chug on. Engine failed about 1/2 mile from boat ramp, had to tow 35-foot sloop with my 3.3 hp outboard on the inflatable for the last leg in the harbor, which was quite exciting. Fortunately, the wind was light and not much traffic.
CajunSpike's detailed explanation of my photo is right-on, thanks for filling in where I deserted.
I'll probably not repair this engine since I've had a number of problems with it over the last few seasons mostly relating to being worn-out. Since it has already been re-sleeved before me and I did a valve job 2 years ago, time to move on.
I like Al's idea of "chamber of horrors", just don't like providing the first example.
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  #27   IP: 71.81.49.245
Old 11-04-2018, 02:40 PM
Scott312 Scott312 is offline
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Pulled the spark plug wires one by one to see if the problem could be isolated.

Seems like it sounds better when #3 was disconnected and not firing. Any other advice, not sure what the next step should be.

Thanks in advance!
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  #28   IP: 70.186.108.69
Old 11-04-2018, 03:46 PM
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CajunSpike CajunSpike is offline
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If you pull the plug in the suspected cylinder and rotate the motor till its tdc, you can just see the edge of the piston in question. One tiny way to see if the piston is mostly intact at least.
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  #29   IP: 131.162.64.51
Old 11-05-2018, 09:27 AM
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Peter Peter is offline
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Quote:
Originally Posted by Scott312 View Post
Pulled the spark plug wires one by one to see if the problem could be isolated.

Seems like it sounds better when #3 was disconnected and not firing. Any other advice, not sure what the next step should be.

Thanks in advance!
From https://moyermarine.com/techtip001-2-2-2-2/ - Elevated Exhaust System Backpressure

"A valuable diagnostic technique was discovered during this episode. Whenever any one of the four spark plug wires was removed, this particular engine ran and even accelerated somewhat better. Clearly, by the time a restriction grows to this extent, the exhaust system is only capable of handling a three cylinder engine. As soon as the forth cylinder is added, the engine bogs down due to being unable to discharge its exhaust."

The sure fire diagnostic would be to measure the back pressure but unless you have the appropriate exhaust flange that will be hard to do.

Second would be to disconnect the exhaust from the manifold and see if it runs better. I have never done this and suspect caution would be required to ensure

1) water does not come back form the disconnected exhaust
2) exhaust fumes do not build up in the boat

I have no doubt more experienced forumites can advise further.

Peter
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  #30   IP: 71.81.49.245
Old 11-10-2018, 11:59 AM
Scott312 Scott312 is offline
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Checked the exhaust with a borescope through the water injection tube, good condition.

Checked #3 piston with borescope, piston still there!

Pulled the manifold, and the valve cover - #2 had a stuck exhaust valve.

Not sure if we found THE problem, but we definitely found A problem...
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Last edited by Scott312; 11-12-2018 at 06:18 PM.
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  #31   IP: 174.218.133.115
Old 11-12-2018, 07:03 AM
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edwardc edwardc is offline
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That spring also looks funny, like there's a bit missing off the end.
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  #32   IP: 97.93.70.7
Old 11-12-2018, 10:00 AM
Dave Neptune Dave Neptune is offline
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Edward, I agree. I see at least 2 coils missing and a buggered end under the retainer cap. Makes me wonder where the pieces are.

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  #33   IP: 71.81.49.245
Old 11-12-2018, 06:23 PM
Scott312 Scott312 is offline
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I didnt think to count the coils. The angle on the pic may be hiding some of them. Will check it out in a day or two.
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