Exhaust problem?

[sailhog]

The saga continues....

I removed the hot section from the manifold yesterday, and the engine started right up. It started with unbelievable ease. Thus, I thought the problem I was having was the result of a blockage in the exhaust system. As I searched for the blockage, I tried blowing on the wire/rubber exhaust hose, and couldn't blow out. I took the hose apart where two sections meet in the port lazarret, and blew on both sections (forward and aft). The aft section was completely clear, and the forward section ejected a significant amount of water into the cabin. When I hooked everything back up, the motor started right away, however, with more difficulty than when the hot section was removed. I opened the raw water seacock, the muffler lift and hose filled with water, and she continued to run. But it was struggling.... Finally she petered out....

Other symptoms the engine is experiencing:
1.) I have to continuously prime the fuel system with a priming bulb, even though I've established that the fuel pump is operational. Also, I've replaced all of the fuel lines, the priming bulb, and removed the gate valve above the take-up tube (as I've heard they are often the source of air leaks).

2.) The sparks are completely dry after trying and failing to start the engine.

3.) Compression is 91, 76, 92, 60.

4.) There is plenty of fuel in the carb bowl.


So what could be causing this engine to fail to start?

Could there be too much water in the exhaust hose, or a relatively small restriction that is causing it to pool and create back pressure?

Once again, I appreciate everyone's help.
Best wishes,
Dwight

[smosher]

If a hose restriction was holding a fair amount of water, then its wasn't a small restriction,
it had to conpletely collapse. The inner lining has collpased upon itself not allowing all of the exhause gas to escape. This exhaust gas pushes the water out of the boat when its not working correctly, water tends to end up in the manifold.

Replace it, its not expensive and put on new clamps too.

This could also be your problem with starting as the engine cannot suck in air

Where exactly was the pipe with the water connected to ?

Steve

[sailhog]

Smosher,
The exhaust hose exits the water muffler lift, ascends up through the galley sink fittings, then dives down into the forward area of the port lazaret, then ascends up to the top of the port lazaret before diving down to exit through the transom.

It seems that the water and gas has to make an additional ascent on my C-30. The water that I'd blown out with my lungs was in the first dip after the water muffler lift.

Thanks.

[hanleyclifford]

There is your problem! That second "dive" creates an unnecessary pooling place for water. Once the exhaust exits the water lift it should rise continuously to the highest point in the lazarette before decending to the exhaust thru hull.

[Dave Neptune]

Rises

I have three rises in my exhaust and no problems with the extra risers. I doubt you are using 26+ feet of exhaust and risers as in mine and I have no problems at all.

You shouldn't need to keep priming your fuel system. If there is fuel in the carb and the choke is working properly it should start. Have you confirmed the choke is operational?

Have you moved the distributor or the wires?

Dave Neptune

[sailhog]

Hanley, Dave:
The choke is operational with a new cable. The wires are where they should be, and the distributor hasn't been moved. I adjusted the timing myself, and it seems to be where it should be. I tightened up the points a tad (.018) and put new plugs in. The engine is alive with electricity. I've zapped the bejesus out of myself a couple of times checking for spark at the plugs. It's there.

The engine runs starts instantly w/o the hot section attached. However, the atmosphere in the cabin is significantly degraded when so detached. A couple of posts have mentioned the A-4's sensitivity to exhaust back pressure, and I'm inclined to believe them.

Tomorrow I'd like to replace the first four feet of the 1-5/8t wire/rubber exhaust hose. Perhaps it has degraded and is a partial obstruction and causing additional back pressure?

These comments from my fellow sailors are tres helpful. Mucho, mucho. Keep them coming, SVP.

[ndutton]

Because my boat is getting long in the tooth I tend to approach repairs aggressively so please take what follows for what it's worth which is exactly what you paid for it.

If it were me and the engine started and ran well without the exhaust but not so with the exhaust, I'd be installing a complete new exhaust from the manifold flange all the way to the transom, waterlift included. That way it should last another 35 years and I could put it out of my mind. Any performance problems that develop afterward simply cannot be due to the exhaust.

I've said it before, I've been blessed with an easy starting, smooth running engine but even so, in the past 6 years and not due to failure of any sort I have:

• 100% new fuel lines
• new electric fuel pump
• new shutoff fuel valve ahead of the carb
• 100% new engine wiring
• new engine control panel
• new waterlift
• new hot section w/ new mixer
• upgrade to electronic ignition
• new flamethrower coil
• new alternator
• new, larger raw water intake thru-hull and valve
• new raw water strainer
• new raw water flushing Tee
• new throttle, shift and choke cables
• and with my recent conversion to FWC, 100% new coolant fittings and hoses as well as a physical cleanout of the water jacket

and this in addition to normal maintenance (plugs, oil, filter, etc.)

I figure with a boat as old as mine, it was due for wholesale replacement of systems.

Anyway, that's been my strategy and it has worked for me.

[sailhog]

Neil,
I'm right up there with you. I've got new:

carb
manifold
hot section
raw water pump
engine-side ignition
starter
head gaskets
coil
fuel lines, racor, polishing filter

I'm ready to replace something that isn't working....

The water muffler lift is fine, but it's the first few feet of hose coming out of it that concerns me now.

We had heavy-duty rain storm roll through here this afternoon, and I'm happy to report that the deck is tight as a drum. Not a drop made inside. Went crazy with the 3 lbs. sledge and the silicone over the past few weeks....

I'm ready to cruise the weirdly clear waters of the NE Gulf.... Just need a few minutes of reliable aux to mitigate the dock rash....

[ndutton]

Are you sure the waterlift is fine? I've read more than one story around here about waterlifts half filled with debris. I'm not saying I have any indication that there's a problem with yours, I couldn't possibly know. I'm only thinking with as much as you've been through chasing these issues, at this stage I wouldn't assume anything. I'd need cold hard evidence that something was good before passing it by.

As I said, I tend to replace rather than keep if for no other reason than old age. I even replace functioning components and sometimes whole systems. IMHO, it really pays off in the end.

Tomorrow I'd like to replace the first four feet of the 1-5/8t wire/rubber exhaust hose.

Then that new 4 feet will be connected to 10 or more feet of 30+ year old hose.

Sorry, I don't mean to nag.

[sailhog]

I took the waterlift off the boat, emptied it and cleaned it up. So far as I could see, it was fine. I believe the hose is only nine years old. The boat underwent a substantial refit back in 2002.... and she's undergoing another in 2011!

So, if the manifold is in good shape, and the waterlift is in good shape, and the engine still won't start with the exhaust attached, I'm thinking I should look at the hose. Is there any reason having to do with the engine itself that would keep it from starting with the exhaust disconnected? Thinking out loud here....

As always, thanks....

[ndutton]

OK, now I'm getting confused. In post #10 you asked

Is there any reason having to do with the engine itself that would keep it from starting with the exhaust disconnected?

but earlier in post #6 you already said

The engine runs starts instantly w/o the hot section attached.

I'm struggling to reconcile the two statements.

In the first post you said you've had to constantly prime the fuel system with the squeezy bulb. Was this also true with the instant start and run report in post #6?

[TomG]

Dwight,

I replaced my exhaust system from the manifold to the thru-hull. Like Neil, I tend to replace things ahead of time rather than "on-condition" as we say in aviation. I was concerned mostly with my waterlift can, but I also wanted to go with a new(old) design and incorporate the Tartan Standpipe that Don sells here. Although the MMI Standpipe is quite a bit more expensive up front, the benefits longer term are exponetial. If I recall correctly, the C-30's layout precludes the use of a standpipe, so I'm not trying to sell you one of those, but I just wanted to give some context to how I came about my discovery.

My T-30 has a three-year-old rebuilt MMI engine. She is a beaut, with all the bells and whistles. Believing that the proper care and feeding of machinery pays great dividends, I removed the old waterlift to install the new standpipe. When I cut out the waterlift, here is what the inside of the hose looked like:


This is a cross-section of the hose leading out of the waterlift UP to the vented loop in an engine that was running! This wasn't the section just downstream of the mixing elbow, this was downstream of the lift. The whole inner liner had completely collapsed. Be sure of the integrity of the exhaust hose. You might be able to find a soft spot by squeezing the hose. If you do, I would certainly consider a collapsed hose.

Also, you indicated in an earlier post that your exhaust makes two ascents (one from the lift and another aft of the galley in the port lazarette). I think this is a real "no-no" as it essentially creates a "double water lift." If you think about it, the engine exhaust has to create enough pressure to raise the cooling water out of the lift. This is okay except when you have another block downstream. Since air is compressible and water is not (for our intents and purposes), water that gets caught in the low point of the exhaust hose in the lazarette has to be pushed out by the exhaust that also has to overcome the waterlift. So as the engine pushes the water out of the water lift, it simply backs up against the blockage in the low point until the air is compressed enough to squeeze by the low point. Even if the hose hasn't collapsed, it is essentially extremely restricted at that point creating a great deal of back pressure. If you truly do have two "lifts" in your system, I would fix this first, and then see what happens.

Here's an interesting link: ABYC Exhaust Systems

I'm sure others with greater experience than me will chime in, but I will offer this observation free of charge: The A-4 uses an "updraft" type carb. This simply uses our old friend Bernoulli to suck gas out of the carb bowl through a venturi where it is then supplied to the combustion chambers. If the exhaust system is truly and well blocked, I doubt there is much intake going on, since there is no place for the exhaust to go. If there isn't any intake, there will not be any gas drawn into the cylinders. If the engine runs well with the manifold off, then you've narrowed the scope of the problem considerably. I would be curious to know your cylinder compression with the manifold (or exhaust pipe) off.

Best of luck,

[sailhog]

Tom,
My exhaust hose appears to be completely clear and in good shape -- even the section immediately down stream of the waterlift. I inserted a section of cable into it just to make sure it was clear, and about three feet in the cable hit something, but it turned out to be the interior "connector tube" where two sections meet. After wiggling the cable around, it continued to make its way downstream, until it came to the second connector at the summit of the second ascent in the lazarette. I'm wondering if these connecting sections are sufficiently impeding the exit of water, creating pools (second muffler lifts) and excessive back pressure. The C-30 has remarkably poor access to the exhaust
hose, which is probably why it was installed in sections....

Thanks for your post. I love those T-30s....

Neil,
Sorry for the confusion. I meant to say: "Is there any reason for the engine to fail to start with the exhaust CONNECTED due to excessive back pressure, the problem being enhanced by an engine-side deficiency." I was thinking that inadequate compression, for instance, might make the engine more susceptible to back pressure. I didn't state that very well.... My mind is turning on itself....

Regarding the priming bulb, when the engine ran a few days ago, the priming bulb would soften, as though the siphon effect had been breached. Maybe I should just tackle one problem at a time.... Sorry for the confusion....

Thanks for your help. I appreciate your patience and expertise.

Dwight

[sailhog]

One more detail to add....

My exhaust hose is 1-5/8 inches in diameter.... I've noticed on other threads that smaller diameters are often used. I believe Dave N. warned against larger diameters, as they allow for larger batches of water, creating excessive back pressure. Any thoughts on this?

[ndutton]

One more detail to add....

My exhaust hose is 1-5/8 inches in diameter.... I've noticed on other threads that smaller diameters are often used. I believe Dave N. warned against larger diameters, as they allow for larger batches of water, creating excessive back pressure. Any thoughts on this?

There are two camps on opposite sides of that question but I'll offer that in a poll on exhaust size last year the majority of responders had 1 5/8" hose - as do I - with no problems.

As to whether or not they'll prevent an engine from running I think depends on a number of factors but dips or traps in a waterlift exhaust line are bad form and should be avoided. It's clear to me your exhaust line is not factory original and whoever replaced it introduced the traps and associated elevated backpressure. As you're replacing exhaust components it would be to your advantage to secure the hose up to eliminate the traps.

I'm confident with all the issues you're resolving along this journey that you'll have a good running engine when you're done.

Hang in there.