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  #1   IP: 76.95.236.166
Old 03-01-2021, 10:59 AM
chrisoelder chrisoelder is offline
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No Compression in #4

Hi All!

I have a small issue that I noticed yesterday while out. I noticed that the engine seemed to be having some trouble at the base RPM. She would only stall when in gear and throttling up (not every time). After the sail, I started to do some basic troubleshooting and realized I have zero compression in the #4 spark plug. This would make sense why the engine seems to be struggling a bit. Did some research here and determined that my valve must be stuck open. I tried a bit of oil and WD40 but no luck. Still no compression. I ran out and grabbed some MMO to give that a try this week but wanted to reach out here and see if you guys had any other theories or ideas of how to resolve this compression issue.

I have been thinking about giving the engine an acid rinse, do you think that could help with the valve?

A week before this last sail I did a tune-up: Changed the fuel separator, replaced spark plugs, replaced the raw water impeller, and gave her an oil change. I topped off the fuel separator with a bit of seafoam and added a bit of MMO to my oil change. Not sure if this info is important but wanted to share incase

Thanks!
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  #2   IP: 155.186.122.195
Old 03-01-2021, 11:53 AM
Dave Neptune Dave Neptune is online now
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First an "acid flush" would have absolutely nothing to do with the valve.

Sounds just like a stuck valve. Often you can get the valve loose by using an allen wrench to move the valve through the plug hole or remove the side plate and get it loose that way. But first try "spraying" into the cylinder while cranking the engine with the water valve and ignition off. let the oil soak and repeat a few times over a couple of days.

Now to the fuel. How much and what additives have you mixed into the fuel?

Adding some TCW-3 (best) or MMO to the fuel and running her for a bit will often "shake" the valve loose and the oil in the fuel will get "on the valve stems" and clean things up after some hours of running. Don't use to much or many products. I mix the lubricants into the fuel at around 100:1 or a bit richer.

Dave Neptune
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  #3   IP: 76.95.236.166
Old 03-01-2021, 12:49 PM
chrisoelder chrisoelder is offline
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@Dave Neptune - thank you for the quick reply!

RE: Acid Flush, excellent! Good to know!

When you spray into the cylinders are you only using oil or are you using a mixture of ATF and oil? Possibly some Acetone to help remove any possible carbon build-up?

Excuse this dumb question: when you say spraying you are saying to put a small amount of oil in the plughole. not actually spray oil into the plug hole right?

I haven't added any lubricants to the fuel since I found the issue but I am planning on doing that. I normally add a small splash of MMO when filling the tank.
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  #4   IP: 155.186.122.195
Old 03-01-2021, 01:22 PM
Dave Neptune Dave Neptune is online now
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Yes, use a spray and spray directly in and towards the valves. The spray will get to the "valve stems" better than just pouring some in. Any good spray lube WD-40, Tri-flo, garage door oil or pretty much any spray lube. Do spray towards the valves and if you can crank the engine at the same time do so. Also use a rag to catch the bit of spray being shoved out of the cylinder when cranking.

Hint, do remove all of the plugs so the engine will spin faster on the starter. ONLY spray into the offending cylinder so starting will be easier without the other 3 plugs having to deal with burning all that was sprayed in, when ready to try.

It may take a few cycles of the above but they will usually get loose with patience.

Dave Neptune
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  #5   IP: 76.95.236.166
Old 03-01-2021, 02:21 PM
chrisoelder chrisoelder is offline
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Excellent! Thank you for the breakdown. I am going to give this a try over the next week.

I will let you know how it goes and if I can get some compression

Thanks!
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  #6   IP: 155.186.122.195
Old 03-01-2021, 04:10 PM
Dave Neptune Dave Neptune is online now
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Since your fuel is just fuel go ahead and add some TCW-3 (2 stroke synthetic grade) or MMO guess your fuel in the tank and add enough "top oil" to get a bit richer than 100:1, it won't smoke and it's also very good for the rings while keeping oil on the valve stems, a good thing.

I ran my engine with TCW-3 for over 30 years and didn't loose any performance or a drop in compression numbers in fact they did go up a bit.

Dave Neptune
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