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Crusader 350 Repeated Stalling at less than 1100 RPM

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bonanzas35

New member
I have twin carburetor crusader 350 engines with approximately 300 hours on complete overhauls. After several years of satisfactory operation, the port engine (only) came out of winterization having a repetitive engine stalling problem after warmup. Racor fuel filter checked out OK.
The engine stalling is only present below 1100 rpm regardless of whether the engine is in or out of gear. Slower rpm results in more frequent stalling. Hitting the starter switch results in immediate restart.
Complete rebuild of the carburetor made no improvement. Engine operation above 1100 rpm is satisfactory and achieves full rated rpm.
Mystified!
 
How complete was the carb rebuild?

I take it these are Model 350's (454 BBCs) and there is no indication of rich running in the exhaust?
 
Carb rebuild was represented as a complete shop rebuild using a full kit.
After installation, the installer spent time setting up the idle mixture and idle speed. Speed set to approximately 700 rpm in neutral gear and just over 600 rpm in gear. No obvious evidence of rich idle mixture however, the exhaust is an underwater discharge (amidship) which is a little hard to "read".

Proposed "fix" by the same shop is carb replacement with a "overhaul facility" rebuilt carb. Say they suspect something amiss in the idle circuit that was not found during the shop overhaul.

Idle stalling problem only starts after 15 to 20 minutes of running time including both cruise and idle operation.

Still mystified.
 
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Did the installer give you any details regarding the function of the idle mixture screws? In other words, did adjusting the screws change the air/fuel mixture delivered?

Sad to say but most shop rebuilds do not clean the idle channels adequately. Sounds to me like you have insufficient fuel flowing thru the idle path which causes the stalling below 1100 rpm. The main system on most carbs will start to flow fuel above 1000 rpm.

An overhauled unit is probably the fastest method to resolve your issue but won't be the most economic option.
 
The installer noted that changing the idle mixture did affect the idle rpm. I could also hear and see a change in rpm while he was changing the idle mixture.

Carb change scheduled for this afternoon. Will check for results as soon as the wind subsides later today.

Thanks for your observations.
 
I went through that on one of my engines as well. Very frustrating! Kept tinkering with it and it went away on its own. It's the carb, no doubt.

Jeff
 
Put on another overhauled carb. Problem almost exactly the same as the original carb and overhauled original carb. So, same problem with 3 iterations of carburetors.
Problem also time related and repeatable. Stalling problem begins after 25 minutes of running. Engine cuts out at 850 rpm at 30 to 50 second intervals. At 950 rpm, cuts out at 60 to 80 second intervals. In all cases, the engine restarts immediately with a bump of the starter. At 1050+ rpm, engine does not cut out.
Totally normal operation above 1050 through normal cruise at 3000-3100 rpm.
Anyone traced a similar problem to an aftermarket electronic ignition?
 
Hi Bonanza,
You did not give us the yr. of the motor. On some of the newer carbed models the electric fuel pump is energized during cranking and kept running via pressure on the oil pressure switch. If the carb bowls are filling during cranking and not being replenished via the oil pressure/fuel pump switch you might be running the carb dry resulting in your stalling issues. If the oil pressure is low at low rpm or if the oil pressure/fuel pump switch reads it as low, you can see where it would not supply current to the fuel pump. The fact that the motor can reach and maintain cruise rpms makes me suspicious of low oil pressure or a def. oil press/fuel pump switch as areas of concern at least regarding the fuel system.






Good Luck
Jon C. Allen
 
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Great observation; very possible indeed.

sounds like a test light and pressure gauge are prerequisites for his next trip to the boat.
 
Did you ever find out what the problem was? I have the same problem and tried the same fixes and still the same problem. My engine is a 1987 and has a mechanical fuel pump. Replaced the distributor last year and put in an electronic model. Just about everything replaced in the last year.
 
Something getting warm and failing. Ignition coil comes to mind. Higher dwell at low rpms maybe causing more heat. Is the coil too hot? Is there a ballast resistor?
 
I picked up an '85 silverton 34 with twin 270 crusaders this summer. Starboard eng has same problem. The problem is more intermitant. At idle either warming up or underway slow run, the enginge randomly dies. Starts right back up. Not a problem at cruise RPM's. The stalling doesn't happen all the time, it culd be hours into the day. when it stalls, it can be morie frequent.

It is a problem because my mechanic is puzzled and it won't happen for them. They adjusted carb. Next is to change the coil, condenser, cap and rotor.
 
Both of you need to pull the coil wire and crank it over to check for spark the instant the motor dies! Don't wait a second. I suspect that this is an ignition, not carb problem.

Note: Carb problems are slow reacting; ignition problems tend to be instantaneous.

Jeff
 
I had this issue. It was a short in a DC wiring to a bilge alarm. This ruined the alternator and several batteries. You could watch the power drop on a meter and when it got to low to fire the ignition, the engine died. Three mechanics and one marine electrician missed it, finally got my meter out and found and fixed it myself.
 
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