Sudden loss of power

[AIM]

This is my first posting on the A4 forum so bear with me if I make some obvious mistakes.

I just put my Triton in the water to make the 2 hour journey from the yard to my mooring. For one and three quarter hours everything was going swimmingly. I was making over six knots and the engine was purring. Just rebuilt the carb, changed the plugs, new raw water impeller, new plugs, new thermostat and bypass, new oil.

Then suddenly everything went south. Sudden loss of power, but not complete loss. Engine clearly not firing right. Excessive vibration. I was able to limp home to the mooring with the speed getting slower and slower. By the time I arrived I was barely making 2 knots. I sounded like one of those old popping diesel engines

At first I thought something may have snagged the prop but symptoms continue when shifted to neutral.

My gut tells me this is distributor or timing related, but with my limited mechanical know how I'm not sure if that's worth much. What I can tell you is that it seemed to be a singular event - working perfectly one second then clearly something was wrong.

The oil pressure stayed good the whole time. Water flowed from the exhaust with no problem. The temperature gauge definitely went way down.

I guess I'll start by replacing the distributor or at least parts of it. If this seems symptomatic of something else or if I have left out some valuable information please weigh in.

Thanks.

[Mo]

Hi,
Well, it could be many things. But I will just list off some OK. You will have to check each one. Typically, if the timing bolt was tight it's probably not timing...so we probably don't have to look right there first.

-check all plug wires and ensure one or two didn't chafe on the alternator or something.
-ensure all wires are on securely
-coil malfunction can cause loss of power and ignition. Allot of times the coil issue results in complete loss of power....other times it just misses and looses power. Should you start the engine when it cools down and it runs fine the coil should be the main suspect at that time.
-sometimes a valve or valve spring can be damaged. This typically doesn't happen underway and under load, but it is something to keep in the back of your mind.
-remove plugs and look and see if there is water on them. Gas looks wet...water leaves a bubble. If your manifold developed a rust hole or something it could be spraying water into the combustion chamber and putting out the fire...again, could happen.
-water in fuel will cause loss of power and sputtering.
-something on the prop can slow the boat and

***with all that said, is sure sounds like an ignition problem. Allot of people get fixated on prop and vibration. The reverberation of a poorly firing engine can radiate sound to the drive train and it can feel like the shaft is coming out of the boat...knocking and banging.

[Dave Neptune]

Question & quick check

AIM, did you try the choke? And if so what happened?

When an engine looses power or begins to stutter a good check is to engage the choke and see if it helps while engaging slowly.

Dave Neptune

[ndutton]

My first instinct was fuel all the way but that was a knee jerk reaction.

Rough running and popping all of a sudden makes me wonder if the distributor was fastened tight. If not, the rotation of the dist shaft would try to twist the dist body clockwise resulting in severely retarded timing. As it continued to move the symptom would worsen.

Grab the distributor and see if it rotates by hand.

[Al Schober]

Like Neil, my first reaction was FUEL. Clogged main jet, sediment in tank disturbed by the passage, etc. But you know your fuel system better than I do (tank clean?, primary and secondary filters?, etc) so I could be wrong. But try pulling out the choke and see if it runs better. If so, clean the main jet.
Ignition? Perhaps the distributor shifted a bit? Broken advance spring? Probably not a bad coil - a bad coil and the engine dies like it was shot! ..until it cools off.

[Easy Rider]

Try replacing the condenser. The one in there now might be defective even if is newish. Sounds just like what I went through a few years ago the only time in 27 years the A4 let me down.

[AIM]

Thanks for all the replies.

I will be returning to the boat in a few days and will get back to you.

Is replacing the condenser a straightforward proceedure?
Just about everything I do now will be for the first time

thanks again
AIM

[Easy Rider]

Changing the condenser is easy if you can see what you have to do. Just be careful not to drop the little bolt that holds it in place.

[tenders]

I agree with your gut, that you should look carefully at your distributor cap and rotor. Label the plug wires and where they go onto the cap very carefully before taking them off!! Replacing both is cheap and easy.

The cap might have cracked or worked its way loose, resulting in misalignment with the rotor and inconsistent firing.
The cap contacts underneath might be carboned up or worn - wipe with a bit of acetone or replace it
The rotor might be broken or worn.

The rotor spins around pretty fast as the engine runs - it's been interesting to me to see how hosed up it and the cap can be even though the engine runs pretty well.

I do agree with the suggestion that you convert to electronic ignition, as it helps rule out condenser and points issues that are possible but not likely causes here - but I would NOT do that until this has been solved. This is going to be caused by one minor thing out of a lot of potential minor things, and there is no need to introduce more variables into the equation.

[ArtJ]

As mentioned by others , I would bleed the carb thru the main passage plug. A common
issue when gas has been stored over the winter. I would also check
that all the plugs are firing by removing wires one by one and looking
for difference in rpm. Remove plugs and look for fouling as well.

[AIM]

Once again thanks for the replies.
You have no idea welcome these tips are.

I was thinking about it overnight and I think the fuel idea could be right.
I will also plan on replacing the distributor cap and condenser as a precaution.

So I can flush the carb without having to remove it? i'm dreading removing it while the boat is in the water. Well to be more accurate I'm dreading having to put it back on while the boat is in the water. I barely have enough room to get my hand in between the carb and the bulkhead. Reattaching the choke cable and its housing was a royal PITA. I ended up changing the screws and nuts to match the tools i could fit into the gap.

I replaced the gas filter a couple of weeks ago. i poured the contents into a clear container and i thought it looked ok (yellower than I expected but no visible particulates). I put some stabilizer in the gas at the end of last season

Do you think I need to drain and flush the whole tank? I'm not sure where I would put all of that gas.

[ArtJ]

You should have a new one of the Fuel water separators that MMI supplies and
also a in line filter before the Carb to keep particles out of carb over season
and during storage.

Don Moyer's Carb flushing procedure involves removing the main
passage plug ( be sure to place rags underneath so don't lose plug in
bilge first. He recommends flushing a cup or so through the passage
hole . Gather the gas in a container and make sure bilge is completely
dry and free of gas fumes before starting.

[ndutton]

i'm dreading removing it while the boat is in the water. Well to be more accurate I'm dreading having to put it back on while the boat is in the water. I barely have enough room to get my hand in between the carb and the bulkhead. Reattaching the choke cable and its housing was a royal PITA. I ended up changing the screws and nuts to match the tools i could fit into the gap.

I don't understand what difference it makes whether the boat is in the water, on the hard or on the moon. It's location doesn't affect carburetor access.

Have you considered cutting a generous access hole on that side of the engine? You'll be removing the carburetor as a regular maintenance routine so you may as well make it as easy as possible. You can always close up the hole with a removable panel or door.

[sastanley]

I hand pumped my mostly full 18 gallon fuel tank last year after it was contaminated with water..I used the $8 multi-use plastic pump from the auto boutique..it was not the quickest, but getting the fill hose off, and getting everything set up took just as long..I duct taped a piece of stiff plastic to the hand pump pick-up hose to keep it from rolling around in the tank, and to get it to the bottom of the tank. The adhesive in the duct tape lasted just long enough to get the fuel out.

I don't even think I finished a beer when the pumping was done. I pumped mine into 3 jerry cans, took it home, got the water out of it about a gallon at a time in a big pitcher (letting the water sink to the bottom and pull the fuel off the top), and I burn it in the lawnmower.

I think the yellow comes from the corn in the fuel. Non-ethanol fuel is NOT yellow, even months later.

Good luck with determining carb access..as mentioned, it really is a regular maintenance item and much easier to work on out of the engine compartment.

[JOHN COOKSON]

Well to be more accurate I'm dreading having to put it back on while the boat is in the water. I barely have enough room to get my hand in between the carb and the bulkhead. Reattaching the choke cable and its housing was a royal PITA. I ended up changing the screws and nuts to match the tools i could fit into the gap.

I scribed a mark on the fixed arm and the carb with a diamond tip pencil so I can reinstall it in the correct position easly. Also I changed over to small nuts that I can get a 1/4" socket on to. No room for a scerw driver.

TRUE GRIT

Edit: AIM - Just read your post #16. Put a crumpled rag under the work area. It will catch the parts you are going to drop.