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  #1   IP: 174.192.7.234
Old 10-24-2016, 07:19 PM
svmisty svmisty is offline
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Question Two cylinders down

Hi, Afourians -

I get no compression in the first and second cylinders nearest the flywheel and farthest from the exhaust. I checked that the valves were closing properly and all appears to open and close desirably.

We put MMO into the first cylinder when its valves appeared closed, let that soak overnight, turned the engine, let the other set of valves soak, tapped on the valves from above with allen wrenches, moved the valves by hand via the access panel behind the carb, and moved the springs around a bit with vice grips. All seemed similar to the working valves. While we were there, we calibrated to spec the clearances between cam and valves. We did compression tests between all these fiddlings. Still zero.

EXCEPT we got 30 psi when we tested immediately after putting some MMO into #1. It couldn't be replicated in #2, and #1 returned to zero after sitting briefly.

Then we ran the engine to heat it up, let her run with throttle completely open for a few minutes, much to the chagrin of our marina neighbors, and 1 and 2 weren't firing. My friend DID seem to notice a slight hissing sound in the vicinity of those two cylinders as if air was escaping somewhere, although we couldn't tell where.

I've attached a photo of the engine. Perhaps its general setup could give you some clues.

Looking forward to helpful advice!!
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  #2   IP: 76.7.96.187
Old 10-25-2016, 09:20 AM
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Marian Claire Marian Claire is offline
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Welcome to the forum.
First thought is a blown head gasket between #1 and #2. Could also be a breach in the cylinder wall between #1 and #2 but much less likely.
Do you have any info on the engines history. Has it run well in the past, any prier compression tests, head gasket replacement, loss of power underway?
Have you verified that the compression gauge is working properly? Did you try it on #3 or #4?
Dan S/V Marian Claire
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  #3   IP: 137.200.32.6
Old 10-25-2016, 09:22 AM
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I was going to say head gasket too. Head removal might be in order or maybe 2 stuck sets of rings???
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  #4   IP: 71.118.13.238
Old 10-25-2016, 11:58 AM
Dave Neptune Dave Neptune is offline
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By the looks of where the water injects it could be stuck rings. If you have access to a stethoscope you can easily find the point of hissing and if hissing was indeed heard a gasket set is in order.

NOTE if there was water in a back (LOWER) cylinder and she was cranked the hydraulic slam could easily breach a weak head gasket.

Dave Neptune
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  #5   IP: 137.200.32.6
Old 10-25-2016, 12:06 PM
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joe_db joe_db is offline
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That might be - I hope it is - a water jacket and not water injection.

Quote:
Originally Posted by Dave Neptune View Post
By the looks of where the water injects it could be stuck rings. If you have access to a stethoscope you can easily find the point of hissing and if hissing was indeed heard a gasket set is in order.

NOTE if there was water in a back (LOWER) cylinder and she was cranked the hydraulic slam could easily breach a weak head gasket.

Dave Neptune
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  #6   IP: 24.53.90.221
Old 10-25-2016, 12:13 PM
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Peter Peter is offline
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Any sign of water in the oil? Is it milky/frothy?

Is the amount of water coming out of the exhaust (assuming raw water cooling) abnormal? Particularly more than usual?

Let's hope not.

Peter
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  #7   IP: 50.163.158.204
Old 10-25-2016, 06:06 PM
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romantic comedy romantic comedy is offline
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This would be a great time to use a leak down tester.

It sends compressed air into the cylinder and you listen for where the air is escaping.

Last edited by romantic comedy; 10-25-2016 at 06:08 PM.
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compression, cylinders, head gasket, valves

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