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I will give that a try. For my own edification—is it possible that the gasket can handle the 15psi coolant pressure test but not the 400psi cylinder pressure? I don't know what really happens when a head gasket fails.

Is it also worth trying a combustion leak test? The stream of bubbles in the expansion tank could be either exhaust or coolant boiling somewhere in the engine. Assuming I got all the air out (I'm fairly confident, but I suppose there could still be a bit lodged somewhere), are there other sources of a bubble stream that I should look into?

Erik

Sorry for the terse description—it's a long story and I'm typing on a small screen. Based on a compression test, it is probably the head gasket.
Erik

After some plumbing work on our M25, we refilled the coolant. We then went through the burping procedure, including hand-pumping coolant through the hot water heater. We also pressure-tested the system with the loaner tool from the auto store. Now the engine consistently overheats, but only at idle speed. If we increase the engine speed, the temperature stays around 160F, and continuously produces a stream of bubbles in the expansion tank. This has been going on long enough that I don't think it is just working an air bubble out of the system. The only other new symptom is an occasional screech, possibly the belt slipping (maybe we need to tighten it a bit, but it doesn't seem too loose) or perhaps a bearing in the coolant pump?

Does this sound like a coolant pump that is going bad and struggling to maintain sufficient flow at low rpm, or is there something else to check? Any thoughts would be appreciated--thanks in advance.
Erik

I'm keen to learn how to work with fiberglass, but I didn't want to make this my first attempt. Maybe I will practice on something that doesn't carry a carbon monoxide risk.

Based on the black water seeping from the cracks, I'm fairly certain the muffler was leaking. The previous owner had the boat in the PNW for twenty years, but I don't know the location before then. There was no hump hose (I'm adding one), so maybe the vibration did the damage. However, there are no visible cracks around the inlet or outlet. It just looks like someone played football with the muffler.

I have no experience with fiberglass repair, so we decided to splurge on the new model from Catalina Direct. It's extremely expensive, but better than exhaust in the boat. The posts on this forum were a big help—we had no problem moving the old and new ones through the door under the sink. Thanks!
Erik

Since we bought our boat we've always smelled diesel exhaust in the salon after motoring. While working under the head sink, I took a close look at our muffler. The top and sides are laced with hairline cracks, and it looks like exhaust/water has been seeping through. All of the posts that I have seen describe problems around the inlet and outlet nipples and the corners, not on the solid faces of the muffler (but I could have missed some relevant posts). Also, it looks like a previous owner coated the area around the drain screw with adhesive of some sort. Based on the attached photos, does this look like the muffler can be repaired?
Erik

Had I owned the boat in 1991, those plugs would be long gone! At least some previous owner removed the ammeter.

But I'm curious, when is it better to solder connections rather than crimp them? Is there a rule of thumb, or is it preference?

Why solder, rather than crimp & heat shrink? I'm planning to replace the wire harness next (the old RV plugs are headed to the dumpster) and I would like to do all this properly.

I spent a long time researching this project, but I somehow missed that thread. The red led's are a great idea--thanks!

As for the wire colors, the factory diagram shows the colors for the wires coming up to the panel, but not the various connections, e.g., from the ignition switch to the glow plug and start buttons, all the instrument ground connections, etc. I could make all the positives red and all the grounds black, but I thought some different colors might make it easier (for me) to follow different paths. It should be a lot simpler after I rewire it, so this really isn't a big deal.

One of my winter projects is to rewire the instrument panel, and I thought some folks might enjoy this "before" photo of the rat's nest.

I also have one question: are there any conventions regarding wire colors for, e.g., the wires that connect the gauge positives, negatives, etc.? I'm aware of the ABYC conventions for the harness wire colors, but I'm curious about the short wires that run between posts on the back of the panel.

Ok, now I get it—I was certain it had to be more complicated than that. Maybe the afternoon spent tracing wires back there did some damage to my brain.

A cable stop is still on the cable, but I don't see any way to attach this end to the cutoff lever. I may be missing something obvious, but I may have lost something on the lever. Hmm.

While I was working in the engine compartment, the fuel cutoff cable popped off the engine. Whatever attached the end of the cable to the lever on the engine disappeared, like a sock in the dryer. Of course, I'm glad this happened while we're tied up at the dock. However, I have no idea how to reattach the cable. I've studied the "Engine stop lever group" diagram in the M25 parts manual, but I still can't see how the cable should be attached. Does anyone know what parts, clamps, clips, etc., might be required?

One of our dock neighbors swore by a modification he had made. He added a Y between the thru hull and the raw water strainer, and he attached a short piece of hose with a plug fitting on the end. He could then unscrew the plug and insert his dinghy pump hose to blow out the thru hull without undoing any clamps. It seems like a fairly regular blow-out might help prevent some of the harder clogs that require a rod. Are there any potential problems with this setup?

We had the same problem when we bought our boat. We finally discovered that there were two leaks. One was through the fuel level sender--the gasket at the base (that sits on the tank) and the seal around the sender in the middle had fine cracks. The other was in the fuel supply for our Espar heater. The fuel standpipe is connected to the fuel line with a 2" piece of flexible hose, and that flexible hose was cracked. We found one, congratulated ourselves on fixing it...then discovered the other. A surprising amount of fuel leaked through when the tank was overfilled, but they were relatively easy to replace.