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Old 03-17-2022, 11:29 AM
StevenMac StevenMac is offline
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Newbie resurrection

Just made an introduction, and this is a follow-up that's more technical and fuel-specific.

I picked up a 1976 C&C 27 Mk III that's been sitting in its slip for two years. The PO pulled the carburetor off for maintenance, and in the process broke the copper line between the electric fuel pump and the carb. He never got back to it and two years went by. So far, with the help of this site and the Moyer manual, I've determined that the engine is build year 1976, with the late model 5-bolt carb. The carb has an adapter flange to accept the scavenge tube from the bottom, and that port on the manifold is plugged. Don't know why. There's another hose that would exit that flange and hold a little aluminum cylindrical thing that fits in a copper elbow coming from the engine. Don't know what that is.

The crank turns by hand, and a compression test was consistent across all cylinders. My thoughts right now are: siphon all gas out of tank, replace the main copper supply line with A1 rubber hose, replace fuel filters. Then re-install carburetor, again using rubber hose to replace the little copper one PO broke, but with an inline polishing filter. This is all to make sure that the first time I try starting the engine after such a long rest, I'm not introducing ancient fuel to the system.

I'd like to hear any suggestions, warnings, etc. I promise to run the blower for a long time before pressing start.

Thank you!
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Old 03-17-2022, 12:09 PM
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Old 03-17-2022, 12:24 PM
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Last edited by StevenMac; 03-17-2022 at 01:05 PM.
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Old 03-17-2022, 12:44 PM
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Hi Steve,

That strange thing coming out of the block is an aftermarket crankcase ventilation valve. The original was just a rubber tube that came out and was sort of aimed at the intake flame arrestor on the carb. The intention was to suck up bad gasses and fumes from the crankcase and burn them in the engine. Some back and forth discussion about wether it's even a good Idea on these engines. I put one on mine but it's not a necessary piece to get started with.

I'd restore the scavenge tube; it's a safety feature.
Regarding running the blower: YES! And remember that a proper installation should not have any gasoline smells.
Tell everyone on board "If you smell something, say something"

Cheers and welcome,

Russ
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Old 03-17-2022, 12:48 PM
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Thanks Russ for identifying the ventilation valve. Any idea why someone would reroute the scavenge tube to a flange adapter and plug the opening in the manifold?

I'm struggling to post pics that aren't obscenely large. Will edit when I get that figured out.
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Old 03-17-2022, 01:54 PM
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Another thought that just occurred to me: perhaps I could disconnect the existing fuel line and hook up an auxiliary fuel tank, like for an outboard. The purpose would be to test out running the engine with new, clean gas before I start getting into all that business with the inboard fuel tank and lines. I figure you all must do something like this when you work on a motor on the bench, right?
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Old 03-17-2022, 03:08 PM
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Quote:
Originally Posted by lat 64 View Post
Hi Steve,

That strange thing coming out of the block is an aftermarket crankcase ventilation valve. ...

Russ
That is from the indigo PCV kit; with that copper elbow.

Name:  PCV.jpg
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Old 03-17-2022, 03:09 PM
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Steve;

While you are adding new fuel hose and polishing filter between the pump and carb, think about also adding a fuel pressure gauge in this location too. It comes in hand when troubleshooting!
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Old 03-17-2022, 04:53 PM
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Thanks guys for the insight. Anyone have thoughts on the portable tank idea as a testing/temporary thing? If it works, I could potentially move the boat out of the PO's slip, which I need to do by the end of this month, or else have it towed.
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Old 03-17-2022, 06:00 PM
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Hello Steve.

Here is a helpful thread on using a portable fuel tank. Note the safety precautions that are mentioned:

https://www.moyermarineforum.com/for...ead.php?t=5633

jack.
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Old 03-17-2022, 10:44 PM
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JACK, that is a thread from the archives!

Steven, get a portable tank with a long enough hose you can keep it up on deck. There are legal implications to all that, such as squeezy bulbs and stuff, but most importantly is you being safe and not blowing yourself up with fumes in the bilge.

Don't worry about the aftermarket PCV fitting for now, but I WOULD solve the mini copper tubing (scavenger tube) issue coming out of the bottom of the carb and normally going back into the manifold via 1/8" NPT fittings.. For fuel feeds, you can use soft hose (i.e., have a barb off the portable tank, soft hose to a 1/8" NPT fitting that goes into the carb) for temp boat moving stuff.

We can work you thru this.
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Last edited by sastanley; 03-17-2022 at 11:02 PM.
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Old 03-18-2022, 02:17 AM
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Thank you, this is precisely the kind of guidance I need. Any reason the "carb-to-carb" scavenge tube needs to be changed back to the original "carb-to-manifold" at least for now? Based on my intuition and what I've learned here, I will hook a fresh auxiliary tank up to the fuel/water separator and try to fire the old girl up.
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Old 03-18-2022, 09:44 AM
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Exclamation

The scavenge tube should be reconnected at the manifold. The "job" of the tube is to collect the raw fuel that precipitates out of the mix in the throat of the manifold at low velocity and drips back down to the carb throat, This fuel should be reintroduced at a point of higher velocity to carry it to the cylinders. That is why it is plumbed into a runner away from the vertical throat of the manifold so that fuel doesn't just fall back down to the throat. This tube is common on most updraft carb installations for SAFETY.

NOTE the tube is just 1/8 copper tubbing. Fittings and tubing are available in most hardware stores.

Dave Neptune
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Old 03-18-2022, 05:55 PM
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Personally, I don't see any difference in the scavenge tube going to that vacuum plate or into the manifold.
The safety item that no one has mentioned yet is the flame arrestor, required to be fitted on the carb inlet.
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Old 03-18-2022, 07:11 PM
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The reason for the carb spacer plate is a vacuum source for the PCV valve. If you're not using the PCV valve, eliminate the spacer plate. You'll have at least 2 fewer possibilities for vacuum leaks.

If you are using the PCV valve be sure it's properly installed before trying to run the engine (see Greg's picture) or else you'll have a massive vacuum leak and she'll never start.
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Old 03-26-2022, 03:27 PM
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Hey hey, everyone. After following the advice I got from here, I gave the motor a shot today. After a couple tries, she fired up and ran! Smoked a bit at first, but that subsided. The oil pressure gauge only came up to 20, so I was a little concerned there. Coolant temp stayed around 180, which I understand is just right for fresh water system. The accessory belt is about done, so I'll look for a replacement tomorrow. But hey, she lives!
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Old 04-04-2022, 03:49 PM
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Another update. After a few short runs with the motor, I drove the boat for several hours from the marina where I bought to another marina where I'll do the rest of the work. The motor seemed to do fine. I stopped by there yesterday, though, and a gasoline smell was pervasive throughout the cabin. I spent a couple hours there washing the deck, with a box fan in the companionway and the blower running the whole time. After I got home, I could smell gas in my sweater. The thing is, when I inspect the connections, I don't see any leaks. I touched the fittings then smelled my finger and got nothing. Is it possible for a fuel connection to leak just fumes, but not liquid?
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Old 04-04-2022, 09:39 PM
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Vapor vs Fluid

The short answer is yes. For example, you have a vent on your gasoline tank. It plays a role bleeding off gasoline vapors and with tank pressure functions for gravity and pumped fuel. There may also be an anti-siphon valve. You could also have a vapor leak on a fuel line that you notice before you notice liquid fuel. I WOULD ELIMINATE ANY IGNITION SOURCE UNTIL I ISOLATED THE LEAK VAPOR OR LIQUID. CONSTANT HIGH VOLUME VENTILATION will speed evaporation. In addition to checking gasoline condition issues, I have thought about buying swabs like this to check fuel lines for leaks, especially connector sites, https://www.amazon.com/Gas-Test-Swab.../dp/B01N5XEZ7M

Wonder if anyone here has tried something like this. Or a cheaper version. Best wishes. Your story is coming along wonderfully. And this setback is another learning opportunity.
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Old 04-04-2022, 11:39 PM
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Thanks Tim. Today I started working on really cleaning the bilge. It assuredly emits a fuel odor, which became more apparent once I began agitating the water. So, I decided I won't be able to determine if there's a fuel leak occurring now until I rid the bilge of any remnant fuel. I figure that when I ran the fan and blower for a good while and then started the engine, I'd aired out any fumes so it was fine, but they might accumulate while the cabin was closed up even without the introduction of new leaking fuel. So I put in bilge soap and filled it up with water, then emptied it (into a bucket!) an hour later. Filled it again with the soap and water, and left it to sit overnight. If I can get it to where there's no describable gasoline smell from bilge, I'll have a much better idea whether I have a leak in the lines. That sensible?
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Old 04-05-2022, 09:50 AM
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Exclamation More

While you have been checking lines have you checked the tank? Often way overlooked are the lines out of the tank that do not feed the carb.

First check for a drip at the low point of the bottom of the fuel tank. Both the "filler hose" and the "vent hose" have probably never been changed out which is good practice for safety. If there cracked replace them.

Dave Neptune
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Old 04-05-2022, 07:02 PM
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One other thought...

You know you have a fuel leak. So that is information.

I have learned here to go end-to-end just like you are doing. Tank, valves, connectors, filters, pressure gauge, carb, you got this. Any location of fluid flow. I have messed up and cross threaded the copper connectors, everything looks tight but the peened/flanged end of my copper tubing really is not tight inside the connector.

Keep the area vented, be sure to ventilate the space with new air volume, not simply circulate air in the space. You probably will find leak on inspection. No ignition sources until you find it (the leak).

If really baffling...

You can borrow a smoke machine and test lines. https://youtu.be/buszJ2jzvWU/

I doubt you will need to go through this subtle diagnostic trouble. The fuel problems on our engines seem to present like a brick bouncing off of the skull.

You got this.
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Old 04-09-2022, 01:07 AM
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After getting the bilge cleaned out and returning to the boat a couple of times, I haven't found any new fuel odors. I'll be out of town for a bit, but when I get back, I will connect the fuel lines with the inboard tank, and this time intend to coat all threaded fittings with permatext form-a-gasket 3, as I've learned that the uncertainty is quite unsettling. For example, coming back to the boat after doing a bunch of cleaning, I open it up and get hit with an odor, which I eventually recognize as Simple Green. But that's pretty strong, so could it be masking gas fumes...etc?
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Old 04-12-2022, 10:55 AM
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The gas fumes sink, so the best way to detect them is to stick your nose in the bilge...however, they should also present themselves when opening the hatch if the boat's been closed up.
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