87 Crusader 270 5.7/350 Stalls at Idle

R

Rybad

Member
Joined
Mar 17, 2005
RO Number
16624
Messages
7
I've been trying to track down an issue of one of my engines stalling at idle, but only after running fine for any length of time. Here is the symptom;

I can fire up both engines, warm to operating temp. and run my boat fine at crusing speed for long as 3 hours non-stop. No engine problems at all. Then, when throttling down to idle/docking speed, the engine will slowly drop out and stall after approximately 5 minutes at idle speed. It will "usually" start right back up, but will stall again in a few minutes exactly the same way. This has been happening for a year. This actually started on port engine, but is not happening on the startboard. The port engine has new electronic ignition system (not conversion, full replacement) and new (rebuilt) carb. Now I'm having the same problem on the stbd. engine. I just ordered the Voyager elec. dist kit for this engine as well, but wont be here until Monday. I'm just wondering if anyone has any suggestions that would back my theory that the electronic dist. kit will solve this problem, or if there are other considerations. I have already changed gas source between tanks, replaced fuel filters etc.. all the basics. On port side I even changed fuel pump and replaced the fuel line from pump to carb. I will be checking choke plate at operating temp see if its open etc.. and maybe swap carbs. Anything else anyone can think of?
 
Does it start to smoke before stalling?
Does it have points? Check gap.
 
What is the age of the gas in the tanks? What does the temp gauges show? Are the alternators still charging at idle?
 
I'm no pro but have the same engines.
There's a stone filter at the carb inlet.
I'd also check the vacuum line and accelerator pump.
Good luck. I know how frustrating it can be!
 
Did you set timing to Crusader specs ( 10* BTDC?) at 750 rpm in Neutral or did you set it by ear and tach or full spec advance at 3-4000 rpm ?
Crusader recommends just setting at idle which is what I always did when I had carbed '88 Crusader 5.7L engines .

Same idle base timing only ( in Time mode) after I had the Voyager EST kits installed too, then of course reset to Run mode. . Loved those Voyagers.

You said you changed fuel tank sources, but is each engine running only off it's own independent tank, with any crossover valve hopefully left closed?
Or are you having the engines run down low 1 tank before switching to the 2nd?

Are you running them on the specified AC MR44T plugs at 0.035" gap, not another brand or hotter or colder plug? ( I have no idea if that plug # has been superceded.)

If the engine has had a recent full tune-up , it could be something as simple as just needing to adjust the idle mix screws a slight bit at a time for highest reading (15-18" ) on a vac test gauge or just by ear and highest tach reading at lowest idle. The vac gauge test can reveal or rule out a lot of other possible issues too.

-But before doing that , you might try putting some carb cleaner in the fuel filter and running that through . And if there is any carbon build-up on the throttle pladed and throat clean that out too.

Lastly , my '88 manual spec 89 octane gas, so if you are using regular 87 that could be another suspect.
 
Sandy:
late timing could cause idle stall but i dont see the rest of it. Flooding or an electrical problem would be my guess.
 
Next time it does it, pull a plug and see if it's carboned up ( black soot/too rich) or white-no color (too lean). This could be float problems. While running, fuel is being used up from the float bowl and the fuel pump is keeping up but the bowl is low on fuel. Bringing to idle, it's running out of gas. OR, it's over filling the float bowl, killing the engine from too much gas (smell the plug...gas fouled)
 
I had the same issue with the same motor. Turned out to be loose bad connection on spark plug wire between cap and coil. Ran ok until coil would overheat and not idle.
Jim
 
If it were me I would rev it up out of gear with the air cleaner off. At a high RPM slam the throttle shut while also blocking off the carb barrels. This will create intense vacuum.
I think your idle circuits in your carbs are partially blocked. I would also get a can of carb cleaner and go at it. Pull the pull the idle jets and idle screws if you can and squirt in there. Shoot a bunch in the bowls.
I could be wrong. I think it's worth a try.
Steve

PS inb4 "you'll drop something in the motor and its dangberous!"
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