Catalina 30, Atomic 4 - Dies no apparent reason

[dbschulz]

First season on 1980 Catalina 30 w/ Atomic 4. This spring she ran great. About the time summer heated up she started to die after leaving mooring. Starts right back then dies again shortly after putting in gear. Fresh fuel w/ MMO, 2 new inline filters & plugs. Fuel tank vent is clear. Plug wires, coil, & carb are fairly new/rebuilt per last owner. Idles fine & sounds great without load but when in gear for a short time slowly shuts down. I have found that when it starts to bog down if I shift into neutral will idle fine, wait few moments put in gear go short distance & repeat. Appreciate advice what to try to get back running smoothly again. Thank you.

[CalebD]

Will it run under load better with the choke engaged? If so maybe one of the 'jets' in the carb is clogged. There is an idle jet and a main jet as I recall. I've gotten pretty good at removing the carb to work on it after 3 or 4 attempts.
If you don't have the MMI A4 manual yet you should think about getting a copy.
It is also possible there is an exhaust system restriction/back pressure situation but hopefully it is just your carb.
Disclaimer: I'm not an expert. I've only 'owned' an A4 for about 8 years. Sometimes I think that it owns me!

[Dave Neptune]

Slow and then go

I had a similar issue and it turned out to be the mechanical fuel pump was no longer moving enough fuel. Rebuilt the pump and no more problem.

It does sound like fuel delivery issue. When it's there it runs as it the fuel fades away so does the power until it dies. If it's an electirc punp check the preassure at the carb.

Dave Neptune

[dbschulz]

I have not applied partial choke when it starts to bog down, but will give it a try.

I do have a MMI A4 manual, but I have not pulled the carb off yet. Sounds like that will be the next step.

After viewing other similar posts I was wondering about the exhaust system back pressure. May have to get into that sooner than I planned on.

This A4 has the electric fuel pump. After I changed the two inline fuel filters I pumped about a quart of fuel into a glass container to check for possible water/separation, but there was none. Is there a special marine fuel pressure gauge to check the pressure? If so do you have recommendations on where to get one?

Thank you very much for your input!

[hanleyclifford]

I have read a few posts on this forum that suggest the exhaust hose on a Catalina 30 is difficult to access. This means it is a good candidate for trouble. But before getting into that I would check the easy stuff, like the ignition switch.

[sastanley]

Dbschulz,

Hanley is right about the exhaust hose...However, when I acquired my '77 C-30 and noticed the failing exhaust hose, the hose in the worst condition was right near the muffler. The 'hidden' parts were not in nearly as bad a shape. Mine was starting to 'spring out' the rusted wire wound inside.

At any rate, if it is dying unexpectedly, but starts right up, I would think it's an issue with fuel supply...whether the pump or more likely something in the carb...i.e., it sounds like it will run with no load, but when you put it in gear, the load kills it. My issue related to that was a piece of teflon thread tape in the carb bowl/jet. I have since then learned that the gasoline breaks down that silly teflon pretty quick and have removed it from the fuel system. Some people don't use any sealer, but I now use the Permatex #3 for just about everything...on gaskets, & as a thread sealer for the fuel system.

A fuel pressure gauge should provide some more feedback..if the pressure is good and it is still dying, I'd look at the carb itself for a blockage. The symptoms of a clogged exhaust are inability to get to full throttle, but it should not kill the motor.

[dbschulz]

Yes, the exhaust system on Catalina 30's is difficult and hoping to make that a fall/winter project.

I'm not sure when the carb was last overhauled, but it is a newer MMI carb. Is it safe to take it off for cleaning before ordering a kit or will that set it up for potential vacuum leaks?

Thank you for your advice.

-Don S

[hanleyclifford]

If you take the carb apart most likely the gasket will need to be replaced. I like to have parts in hand before disassembling anything. You probably know that we have two recent threads with your symptoms and in both cases an exhaust hose blockage was found to be the problem.

[thatch]

"Catalina 30's unite!"

Don,
Welcome to the Catalina 30/Atomic 4 web site, just kidding guys. Another possibility that falls in line with your symptoms is a blocked fuel pickup in the tank. It can normally be removed with some effort but if it's too stubborn try blowing some air back into that fitting which should clean it up a certain amount, at least for test purposes. While you're in the tank area check for leaks, particularly in the lowest corner. Several of us have had to replace our 30 year old tanks recently because of leaks.
Tom "78 Catalina 30, Kari On"

[CalebD]

This forum is really great.

And the Catalina 30 owners aren't too bad either!
I enjoy watching this group contribute to nearly every post about a problem A4. There isn't much that hasn't been tackled by someone in this group except perhaps a cracked oil pan.

As others have said, check out the carb first as it is the easiest thing to do. It is probably worth having the re-build kit even if you don't really need all of it now. At least it has the gaskets you likely will need. Hopefully that will perk up your A4. If not then you likely know that the exhaust system needs to be looked at next.

This forum can also be a bit like the radio show 'Car Talk'. I'm surprised no one has asked you: "What sound does your A4 make when it loses power in gear and dies?"

[sastanley]

Don, I would have a carb flange gasket in hand before removing the carb as hanley recommended. If you haven't removed it yourself successfully, it will likely come apart in pieces when you separate them. I put a dab of that Permatex on the carb side of the gasket on re-assembly so that hopefully the flange side will come off clean when I need to remove the carb for cleaning.

incidentally, the flange (manifold side of the carb connection) is hard to see, so maybe an inspection mirror would be useful to make sure you've cleaned the flange well to accept the new gasket.

Moyer is great about shipping out parts quickly...I am close, so I can call them at lunch time and I have the parts the next day!
Whenever I order gaskets, I always order two..that way i always have a spare for next time. The price of the gaskets is cheap, so if you gotta pay $10 for shipping, might as well have spares!

[dbschulz]

Step Closer

I believe the issue is going to be the exhaust back pressure.

Without replacement gaskets on hand I chose to not take the carb apart this past weekend. I did find a fair amount of exhaust & water spraying out of a hot section joint, so am still working to take the hot section apart on the water and look for the restriction.

Have any Catalina 30 owners out there done this before and do you have any suggestions, or pitfalls to avoid, on the hot section to the water lift muffler?

Is the water lift muffler as simple as it sounds? Are there baffles or could there be blockage inside the muffler?

I'm off to work on my MMI gasket(s) shopping list...Thanks for everyones input.

[sastanley]

Don,
there are some baffles/different length pipes in the muffler, so it isn't an empty container I don't think. I took my exhaust apart this summer to allow for wrench access for engine alignment, and I completely rebuilt (the exhaust system) just 16 months ago..It came apart pretty easy, but that I am sure was due to its young age. I was able to rinse out the muffler & shake out the debris (mine is the plastic Vetus) but you should be able to hear stuff rattling around in there if debris is in fact in the muffler. The mixer elbow between the hot section & muffler is likely the cause of the blockage..sometimes you can clear it with a metal object like a coat hanger, but it is usually pretty hard stuff and may require removal and chipping away on a bench/vise, etc..

Start spraying any bolts/nuts/studs with PB Blaster so it can sit for a day or two and hopefully loosen up those parts. The repeated heat cycles from cold to hot like to fuse all those parts together!

I found my exhaust hose was failing, my boat is a 1977 hull.

[dbschulz]

Shawn,

I too have a "plastic" muffler. It appears to be permanently attached to a piece of 'leveling' plywood. Does it need to be removed to flush the muffler or dare I reverse flush it with a hose into the bilge?

Do you know how to determine when to replace the muffler? Mine is 30 years old this year.

Thanks for the advice!

-Don

[JOHN COOKSON]

It MAY Not Be The Engine!!!

If you have not done so already check your prop and shaft to see if they are clear.
I had the same problem and symptoms you are having. Cause:There was a big ball of fish line and sea weed wrapped around the prop.

A gummed up "stuffing gland" can cause this problem also.

TRUE GRIT