Griff

Sounds like a fuel/carb issue

TomZ

iTrader: (2)

Griff,

What's your thought on the fuel/carburetion?

This shutting off thing is a new symptom that came up. I'm showing about 8 lbs of fuel pressure, and both carburetors have plenty of fuel. If there was a fuel issue, I would expect the engine to cough and sputter. This seems like someone just turns off the key.

SB

iTrader: (1)

Had one last summer. Pontoon with a 3.0 and Holley 2bbl.

Turned out needle and seat was sticking at times. Fuel would pour out of boosters and kill the engine like a switch was hit. Would take a long time to start, clear itself out, seemingly run okay, then instant die.

I went right for the ignition...all was good. Note: I have an inline spark tester that I used....so clearly could see it working when engine died and was trying to start. Finally took off arrestor, watched top of carb while it was running fine...and then saw the boosters start to poor fuel and then engine die. It was one of the rare times I have seen a N&S stick and fuel not come out of the fuel bowl vent.

SB

iTrader: (1)

Have also had same issue with N&S but not flowing enough fuel. After cranking a bunch enough fuel would get in bowl to start and run....but volume couldn't keep up and motor would just die.

TomZ

iTrader: (2)

A clue?!

Interestingly, when I got the blower and carbs back on the engine, I cranked the engine (without the coil lead connected) to prime the carburetors. I only had one fuel bowl (out of four) fill and produce a pump shot. I couldn't figure it out. I was worried that I had made a mistake rebuilding the carbs because I couldn't get the pump shot. Finally, I pulled a bowl screw, and sure enough no fuel. I found that three out of the four needle and seat assemblies were slammed shut and sticking. These were brand new AED needle and seat assemblies. Finally, I got fuel to the carbs, and fired her up. That's when I started having the erratic spark issue and popping issues. Swapping out the module to my stock Mag original got the engine started, and I was able to run it on the hose. I saw nothing in the way of fuel leaks. I even have a two minute video of the engine running. No hiccups (other than having the wrong module on it). Two days later it wouldn't run at all, and yesterday after replacing the sensor, she fired and ran well for about 15 minutes. Then the trouble started again.

Here's a little bit of a difference and a finding... this go around I ran the engine with the spark arrestor on it. I died so I went to look. I pulled the arrestor off, started the engine (took a little bit), and then saw fuel pouring out of the front carb's rear secondary booster. I cracked open the float adjustment, and got it to calm down, but still, it had done it (this was one of the reasons why I rebuilt the carbs in the first place). Maybe it was doing it again? Not sure. It was dumping fuel though. And thinking about it, it was pig-rich after trying to restart a couple of times. Another thing too... I do have the trailer rather high on the bow. Maybe it isn't even a float or needle and seat issue. Hell, I don't know.

I think I have a few things going on here.

TomZ

iTrader: (2)

Just to restate... there was definitely a problem with the ignition. Replacing the cap and the sensor got her running almost immediately.

Griff

It sounds like its surging at idle. Does it stall on the downward surge?????

Also, what's the timing set at???? With the V6-14, it should probably be set to about 20-24* at idle.
With the V8-24 it would only be 8* so it prob won't idle well there.

TomZ

iTrader: (2)

Before the issue of cutting out, it's had a surging idle. Always has. I've tried to tune it out, but honestly, I haven't had it together long enough to really mess with it, off the dyno. There were no problems running it on the dyno. Since then, the blower has been off for repair, and I did a rebuild of the carbs. I didn't change anything else.

It doesn't stall on the downward leg of the surge. It's totally random. Even etting it run at a high idle (solid 1000-1100 rpm, no surge), she'll quit. No coughing. No sputtering. Just off.

One thing that I haven't tried yet... making sure that the harness connector isn't loose. That's gotten me in the past with other boats. And I was leaning on things in that area while changing the plugs.

distantthunder

I was fighting this issue on a Stingray Maxim 222ss with an older 454 w/ Thunderbolt last week but haven't nailed it down yet. We finally got her to fire up and run with what sounded like a dead miss which cleared on its own briefly, then it would idle for a little bit and shut off. It would do it at High Idle (~1000 RPM) and normal idle. I was at the helm while my friend was in the engine bay and he thought I was turning the key off. Initial inspection showed the bowls were not filling but we didn't get much further than that. The boat was in bad shape when we snagged it last week in Delaware so we decided to do a full tune up anyway (Plugs, wires, cap, rotor, coil, belts, manifolds, risers, water pump, carb rebuild). We pulled the carb last week and rebuilt it over the weekend. I am supposed to go over there tonight to throw it back on with the new manifolds that are arriving today. I will let you know what I find unless you find your solution soon. Have you been able to check the timing while it is running?

Griff

I would start with the coil change. Quick and easy.

I would put a timing light on it when you get it started so you can see exactly what the timing is doing.

Another thought is the possibility of dist gear being bad and timing jumping around.