Maybe the gears?

[outoftheblue]

Hi everyone, this is my first request for help here!

I have a 1967 CAL 36 sailboat with an A4.

Engine runs great....in idle even at high RPM (2000) forever.

I've been having a unique issue for the last few years.

When I engage the transmission and raise the RPM to about 1500, it runs great with good power but in about a minute (every time) the RPM starts slowly dropping and if I let it, it will stall.
I can pull the throttle to keep it going until the end of the range of the cable and it will stall...but slowly, gradually.

What i have done so far:
Replaced the carburetor, installed electric fuel pump, new fuel filter and water separator,thermostat, checked fuel hose, tank vent, compression check,
plugs, points....checked the exhaust for restriction and more.
None of the above changes made any difference, it has been stalling the same way, again, slowly, gradually in gear at higher RPM.

From the beginning I had a feeling it might be the trans or the V drive but don't know how to test that?
The shaft was pulled out and the stuffing box and bushings rebuilt but that mad no difference either?

I had mechanics check it out but eventually they leave without having an idea of how to solve this mystery!

I am very curious what I have missed or how I can move forward?

[roadnsky]

Welcome to the crew! You're in the right place.

Do you know the condition of your exhaust? Last time it was rebuilt?

Also, let's try a simple test...
Try running with the fuel fill cap OFF to see if you get the same results.

[Surcouf]

do you have a pressure gage on the fuel supply just before the carburetor? That would allow to rule out all fuel tank / fuel pump / fuel filters / air ingress issues.

When the engine rpm slows down, have you tried to spray start-pilot on the carb? If the rpm does not change much and keeps going down, it would suggest that fuel supply if adequate, and that engine is not starving fuel.

I recommend also to verify what Jerry mentioned before, regarding exhaust pressure: do you have a exhaust lift? direct exhaust like a Catalina 27? Ever checked if there was no exhaust flex hose pipe crumbling on itself? pluggage in the exhasut? The fact that you run a minute stable tend to show that your manifold is likely not plugged, as it would not even run one minute. But could be a poorly working water lift due to flow restrictions?

anyway, you will find on that forum a few individuals that love these kinds of hard to find issues, especially as you seem to have already been checking quite a few things...

[Dave Neptune]

If it is in the trans as you suspect the resistance necessary to stall would create a good deal of heat. Is the trans area much hotter than the engine block? This is a very doubtful cause of stalling.

When it stalls does it just slowly come to a stop or does it shake a shudder a bit when stopping?

I suspect it is fuel related and a pressure gage would answer that if just a few minutes.

Did you do any checks once stalled like spark?

Dave Neptune

[Dave Neptune]

Oops

Oops I forgot to welcome you to the MMI Afourian Forum.

Dave Neptune

[JOHN COOKSON]

IT COULD BE, IT COULD , IT COULD BE..........

Once the engine starts pull wire off spark plug. If the engine runs better on three cylinders it could be a exhaust system problem.

Rig up a auxiliary fuel tank directly to the fuel pump, bypassing the boats part of the fuel system. It could be a blockage in the pickup tube in the fuel tank or a blocked filter. Run the electric fuel pump straight from the battery. It could be something in the wiring circuit to the fuel pump.
Does choking the engine the engine help? It could be something weird in the carburetor.

Report back with the result of these tests. We'll tell you what to do next.

Others will have other approaches and ideas. Consider them also.

As noted a fuel pressure gauge would be a useful diagnostic tool.

ex TRUE GRIT

[JOHN COOKSON]

MORE FREE ADVICE

Hi everyone, this is my first request for help here!
I had mechanics check it out but eventually they leave without having an idea of how to solve this mystery!
?

DITCH THE MECHANIC!!!! "Mechanics" are for the most part are a waste of time and money for an A4.
You have several tests mentioned so far in this thread. Report back with the results. Your engine will run correctly. No ifs, ands, or buts.

ex TRUE GRIT

[JOHN COOKSON]

If it is in the trans as you suspect the resistance necessary to stall would create a good deal of heat. Is the trans area much hotter than the engine block? This is a very doubtful cause of stalling.
Dave Neptune

Is the prop fouled?
The prop can be fouled and whatever is fouling it sort of stays a ball around the prop at low RPMs and is flung out by centrifugal force at higher RPMs causing the engine to stall. (Don't ask how I know this.)
Maybe the reason neither you or the "mechanic" could not find the engine problem because there is no engine problem?

ex TRUE GRIT

[Sam]

Well, you have an impressive list of work done with replacements etc. I also vote for the installation of a liquid filled 0-15ps1 fuel pressure gauge and fitting between the carb and fuel pump [total about $35]. So far you have received a lot good logical advise and I would like to hear the results of running off an auxiliary tank. With a 1967 Cal 36 you have an early model A4 with the small Prestolite distributor [condenser screwed on outside]. If you would like to humor me pull the points plate from the distributor and check the springs and advance weights for proper function, even change springs [moyer] if they are original. Also, the little screw that holds/grounds the condenser may not be original and if the threads are a little too long they penetrate the housing wall and mess up the mechanism.

I have a friend with a restored 31 Chevy with a simple distributor with a manual cabal advance. The cable slipped and wasn't advancing the timing. The engine ran fine in neutral but bogged down under load [going up small hill etc]

[outoftheblue]

Welcome to the crew! You're in the right place.

Do you know the condition of your exhaust? Last time it was rebuilt?

Also, let's try a simple test...
Try running with the fuel fill cap OFF to see if you get the same results.

Hi, thank you for responding. Glad to be here!
I actually removed the whole exhaust system and tested it. it was clean.
i also had the engine run with the cap off.

[outoftheblue]

do you have a pressure gage on the fuel supply just before the carburetor? That would allow to rule out all fuel tank / fuel pump / fuel filters / air ingress issues.

When the engine rpm slows down, have you tried to spray start-pilot on the carb? If the rpm does not change much and keeps going down, it would suggest that fuel supply if adequate, and that engine is not starving fuel.

I recommend also to verify what Jerry mentioned before, regarding exhaust pressure: do you have a exhaust lift? direct exhaust like a Catalina 27? Ever checked if there was no exhaust flex hose pipe crumbling on itself? pluggage in the exhasut? The fact that you run a minute stable tend to show that your manifold is likely not plugged, as it would not even run one minute. But could be a poorly working water lift due to flow restrictions?

anyway, you will find on that forum a few individuals that love these kinds of hard to find issues, especially as you seem to have already been checking quite a few things...

Thank you,

I have checked the exhaust and it has a great water flow out the exhaust pipe.

[outoftheblue]

Once the engine starts pull wire off spark plug. If the engine runs better on three cylinders it could be a exhaust system problem.

Rig up a auxiliary fuel tank directly to the fuel pump, bypassing the boats part of the fuel system. It could be a blockage in the pickup tube in the fuel tank or a blocked filter. Run the electric fuel pump straight from the battery. It could be something in the wiring circuit to the fuel pump.
Does choking the engine the engine help? It could be something weird in the carburetor.

Report back with the result of these tests. We'll tell you what to do next.

Others will have other approaches and ideas. Consider them also.

As noted a fuel pressure gauge would be a useful diagnostic tool.

ex TRUE GRIT

Thank you!
I have ran the engine from a spare tank, connected to the electric fuel pump, no difference but I will repeat because vaguely i rememeber that it ran longer before slowly running out of power but eventually it slowly stalled.
i will repeat the spark plug test but it ran worse on three as far as I remember? I will repeat that.
Chocking, I will ave to try that.
I will test fuel pressure when i get a gauge for that.

[outoftheblue]

Is the prop fouled?
The prop can be fouled and whatever is fouling it sort of stays a ball around the prop at low RPMs and is flung out by centrifugal force at higher RPMs causing the engine to stall. (Don't ask how I know this.)
Maybe the reason neither you or the "mechanic" could not find the engine problem because there is no engine problem?

ex TRUE GRIT

Interesting idea!
I have a two blade folding prop but it is clean.
This stalling issue has been a problem for a long time and boat gets cleaned monthly. It would shake i think when it is off centered?

[outoftheblue]

Well, you have an impressive list of work done with replacements etc. I also vote for the installation of a liquid filled 0-15ps1 fuel pressure gauge and fitting between the carb and fuel pump [total about $35]. So far you have received a lot good logical advise and I would like to hear the results of running off an auxiliary tank. With a 1967 Cal 36 you have an early model A4 with the small Prestolite distributor [condenser screwed on outside]. If you would like to humor me pull the points plate from the distributor and check the springs and advance weights for proper function, even change springs [moyer] if they are original. Also, the little screw that holds/grounds the condenser may not be original and if the threads are a little too long they penetrate the housing wall and mess up the mechanism.

I have a friend with a restored 31 Chevy with a simple distributor with a manual cabal advance. The cable slipped and wasn't advancing the timing. The engine ran fine in neutral but bogged down under load [going up small hill etc]

Thank you, I think checking fuel pressure will have to be done.
On the other hand, originally I had a mechanical fuel pump when this problem started.

I replaced it with the electrical and it had no effect on it. Engine still slowly, gradually lost power after abut a minute in gear sarting at 1500 rpm.

[JOHN COOKSON]

THOUGHT OF ANOHER POSSIBLE CAUSE

After a shutdown check the temperature of the stuffing box with finger or a IR thermometer.

My posts R\E this problem are sort of disjointed I guess. My subconscious is working on the problem. When something pops up in my conscious mind I post. At least I think so.

ex TRUE GRIT