Random tapping

[edwardc]

I would remove the carb first. The manifold is a big heavy part, and you would risk damaging the carb if you left it attached.

[lat 64]

" A good Guide..."

As often happens with a new member, we heartily recommend buying the Manual offered by Moyer Marine. It is written with owners in mind. It would be best to buy and read it completely before starting any repairs of this sort. So many esoteric problems can be avoided or at least foreseen to make it worthwhile.

Do ALL the diagnostics before you tear this apart. That is, make sure where it is leaking—compression test, feeling for leakage etc.
I wonder if soapy water sprayed on the suspect area would help find a leak(??)

If it turns out to be a leaking head gasket, then you can have the opportunity to examine valves too when the head is removed. But, that's a lot of work, so make sure it's necessary first.

[Mo]

My friend Rick had a similar noise a couple of weeks back. Same noise, but it was sloppy, meaning wasn't regular...tap tap tap tap..pause tap tap tap. After much deliberation he took the head off and it was number 4 exhaust valve stuck / sticking. He cleaned it up, and I put the head back on for him and torqued about a week ago. He put the rest of it back together.

He had to take it form there. I cleaned the carb for him as well as it wouldn't start. I've been working quiet a bit lately so wasn't able to give him the full attention. He got it running yesterday, purring like a kitten. He'd put the distributor cap on wrong...screwed up the wiring. I should have noticed that but he's always at his engine and I should never have overlooked it. He'd spent a couple of days trying to get it running and I wasn't around.

[chrisoelder]

Hi All! I stopped by the boat last night and preformed a couple of test. I tried the hand over the manifold and the soapy water.

When i felt my hand over the manifold and behind it i couldn't feel any exhaust. When i added some soapy water to the area in between i saw a lot of bubbles forming towards the back of the manifold, next to the 4th spark plug.

Here is a couple videos i took of it. Please note, most of the smoke you are seeing is steam from the water... if not obvious.

https://drive.google.com/open?id=1pXjmWv_N4g6Ma2ACwvu8mXgWmy0EjM7w

https://drive.google.com/open?id=1BujuFMh99RlaoueyONHtUK5oPCXPVMOI

It would seem like i have a gasket failure, resulting in an exhaust leak. I am wondering if there is a way to patch the area instead of installing a whole new gasket? Something like caulking but made for this reason

A couple more thoughts to the tapping. When i was listening to it last night i felt like i heard the tapping of two metal pieces rather than psst psst, i couldve been mistaken though. Something to note, when i turn up the RPM the tapping does increase to a high frequency. It could be possible that i also have a valve tap and a gasket failure. Could anyone shed some light on this situation?

Here is the video i took of the engine at a high RPM

https://drive.google.com/file/d/1_qoXUNlkj29gPfEMX6OYTGA_RO11gdow/view?usp=sharing

Thanks!
Chris

[capnward]

If a compression test shows good compression in #4, this may only be an exhaust gasket, not a head gasket. Caulking is unlikely to work, but a new exhaust gasket is not that hard to do. Your second video shows more bubbles in that area. I may have a similar issue. Lately my CO detector alarm goes off sometimes. I will have to look into that area.

[lat 64]

That's kind of what I expected. Great way to clean off the engine BTW.

One thing to be aware of though; that is a hot place on the manifold and you must make sure the bubbles are forming from a leak, not boiling water.

I would have expected more spray from such a test(I have never done one myself).
So, consider that the majority of the leak may be on the underside, shooting downward towards the fuel pump.

I agree with capnward, goop will not fix it even for a while. But, perhaps stuffing some fire-resistant material like exhaust wrapping around it for a test will change the noise level a bit and work to help confirm this diagnostic.

Im not ruling out head gasket failure yet. A compression test will give you a comparison evaluation and show good numbers, but pressures are much greater when an engine is running—300 psi or more. A tiny leak in the head gasket would squeak up when running I think.

Still, I think you are closing on the issue.

Keep on,

Russ

[lat 64]

I don't think the head gasket or exhaust valve hanging open is off the table yet. There is minimal combustion pressure on the manifold when the valves are seating properly. Exhaust gases are merely pushed out by the piston on the exhaust stroke (note: well AFTER combustion has occurred). For high pressure combustion gases to escape it has to happen at TDC which is when the valves are supposed to be sealed. This is where the compression test may point us in a direction.

I think Neil(as usual) was on to this back in post #28.

Also, never rule out that more than one thing can go wrong at the same time. It's an old engine.

[chrisoelder]

Hey everyone, thanks for the advice!

I am going to get a spray bottle and give that a shot this weekend. I will also be able to perform a compression test. That should really help figure out whats going on.

Thinking on a possible valve tap - does anyone have any thoughts on the video of the higher RPM with the sound becoming less apparent? Do you think that it might still be related to a failed gasket?

Ill have more info tomorrow or Sunday!

Thanks everyone!


PS: I am ordering the guide with some new gaskets, depending on how the compression tests go

[chrisoelder]

Hey everyone,

Went back down to the boat this weekend and gave the spray bottle test and a compression test. While there i checked my manifold nuts, the 2nd and 1st nuts were a bit loose and tightened them to the 30lbs on my torque wrench. Also i put a bit of MMO in the 4th spark plug chamber and let it sit there for 25 mins (maybe it would unstick anything that was stuck). Engine started up fine and help rpm with no stalls.

The compression test came back with the same exact reading for all chambers, about 50-52. If Im understanding this means that my issue is after the piston, so either exhaust gasket or a valve tap. Please correct me if i am wrong!

Also i tried the spray bottle but i don't think i am getting any conclusive results. I cant tell if im just not getting enough in there or too much water that it boils. Either way i took a couple videos here below:

https://drive.google.com/open?id=1ueYzigE1By8KhYC_sZ4hwVasiqpIsEJU

https://drive.google.com/open?id=1GaNIwSNe-3TNM0wqF1RQ6KswF7aol7Rs

https://drive.google.com/open?id=1L4jXhNP0IOHlXRDYQnjnYPElY8BeQS5f

Also please note, the tapping is becoming a bit different. Less consistent, any idea to what is going on with that and does it help determine the issues?

[lat 64]

Compression test: A bit low; but if they are all similar readings, good. Low numbers might be just a tool-technique issue.

Tapping/pisst sound: it's changed Now it's syncopated! it's got a jazz beat! Really, I think it is now not always making a sound on each revolution.

Less sound/volume: You tightened the manifold nuts. That may have actually put a squeeze on the faulty gasket, making it a tad quieter(?)

A word of caution; that spray bottle may be killing the spark. Try to keep the water off the spark plugs.
Well, at least you're getting the engine clean. Might be time to use some tools though.

Good luck with this. I won't be around a computer for about a month, so no responses from me for awhile.

Russ

[Dave Neptune]

A compression test should be done with the choke open the throttle at full, all spark plugs removed and a good battery.

2 tests should be done, the first one dry and the second test with some oil sprayed into the cylinders.
The first test checks to overall sealing of the cylinder. The wet test will let you know if any low readings were related to valve seating or ring seating.

Did you have the manifold completely open and all of the plugs out when doing your test?

Dave Neptune

[chrisoelder]

@lat 64 Enjoy your time away from screens! Hope you are taking a trip somewhere nice! Thank you for the help and make sure to check back with me to see how it went. Thanks again and have a great one!

@Dave Neptune I actually followed this youtube tutorial with doing the compression test. Didnt know about the other tests

https://www.youtube.com/watch?v=ovvXnd7AhiU

Thanks!