1991 Mercruiser 5.7 350 isles for a few seconds then dies. Help needed - badly

[RoseTopaz]

I can’t figure out what is going on with this boat.

I’ve installed:
New Rochester Quadrajet w/ electric choke
New electric starter
New thermostat
New manual fuel pump
New fuel filter
Blew all hoses out with compressor
Started with the gas cap off
Replaced fuel line from carb to engine
Ran boat with new clean gas
Ran in the lake
Ran on my trailer
Checked vent on tank
New anti-siphon/check valve

What the heck guys. Help me out. I’m running out of **** to replace.


https://m.youtube.com/watch?v=giEw3JsViH4

https://m.youtube.com/watch?v=FnskVWVFDcc

https://m.youtube.com/watch?v=JfxhYrHBcp4

 

[greno]

Ok, things that come to mind:
1. timing is off and you're compensating with idle adjustment
2. float level is not set right
3. carb is set too lean

 

[Rick Stephens]

Start out simple. Get a baseline compression check. Check timing. Prove you have good fuel flow at the carburetor - pull the line and crank the motor with it stuck in a coke bottle. Check for vacuum leaks.

 

[Lewis1111]

Does it shut down around the exact same time every-time it dies? Does it die with a little bit of fuel being sprayed into the carb? How long has the issue been going on? Did it just start or something else has led to it?

 

[thumpar]

Try running off a small tank to rule out anything tank/pickup/line to pump issues completely.

 

[RoseTopaz]

I’ve run it off a separate tank of fresh gas, still died.

it seems to run about the same length of time but I haven’t like timed it. Usually between the count of 5-15 seconds-ish.

When we first got it, it ran fine on the test drive. We got it home and had issues with it kinda not wanting to start. Found out the starter was seized. Replaced that with a new electric one. Then this issue started which turned into the “throw parts at it” you see.

Lewis, how do you spray gas into the carb? I’ll take a stab at it. Also I haven’t had the carb open? viewable? While trying to start it. How do I go about that?

i did test it and it does get the full 12volts to the electric choke when the boat is running. (For the short time it will)

 

[RoseTopaz]

Is there a warm up process I should try? Like let it sit with the key on or something? I usually hook up the water, turn the key and it’ll start. I don’t know if I’m supposed to just let it sit with the key turned but not actually turn to start it?

 

[kenny nunez]

Get a volt meter and connect it to the + side of the coil and check that there is 12-13 volts when the engine is running and when it stops. If you manually close the choke just when it is about to stop will it keep running?

 

[RoseTopaz]

I know when it was/is running the wire the carb is connected it is 12.5~ (Before it takes a **** of course)

i can try manually closing it and seeing what happens.

 

[Maclin]

What do the sparkplugs look like. When was cap & rotor last replaced, or distributor looked at. Is the carb full. I did not see where you had done a fuel pump flow test.

 

[alldodge]

It acts like it has an electric fuel pump. Crank until fuel pumps into the carb and it starts, and once started the key is released and pump stops. It starts but bowl is not full so it only runs a short time. you said this is a mechanical pump but sure doesn't act like it

This also appears to be an inboard ski boat type, which one?

 

[NHGuy]

I just watched your video. In video 1 it is showing that the choke is wide open. That should be adjusted to be closed on startup. And it should open in a couple of minutes while running.
In summer, (now), it's adjusted by loosening the hold downs on the round black electric choke coil and rotating it til the choke is just barely closed.
Then tell us if it still quits after 15 seconds.

 

[thumpar]

Is there a warm up process I should try? Like let it sit with the key on or something? I usually hook up the water, turn the key and it’ll start. I don’t know if I’m supposed to just let it sit with the key turned but not actually turn to start it?

Are you setting the choke? You need to run the throttle forward to close the choke before starting.