4.3 MerCruiser Intermittent Stalling

[NotAGreatMechanic]

This is my first post here. Sorry if it’s a duplicate.
I just bought a 2002 SunTracker Party Deck 21 with a 4.3 I/O MerCruiser. Prior to me buying it the motor had about $5000 worth of work getting rebuilt. Included in that was a new carb. I have an invoice of all the work done and can provide a picture later.
I’ve taken it out about 5 times since buying it. The first two times, it ran great with no issues. The third time, it ran great initially. After fishing for about 30 minutes, I went to move spots. It started up just fine. I gave it throttle and it died. It started up just fine and would idle for a minute before dying. I limped it back to the ramp. Just before getting to the ramp, it started working fine again.
The next time I took it out, we were out for 7 hours with no issues at all.
Yesterday I took it out with a full tank of gas. Ran fine for about an hour and half. Then it started stalling again. We could put it in neutral and increase the rpm’s but anytime it was under a load it would die pretty quickly. It was also pretty choppy yesterday and I noticed the waves would affect how it ran.

Just trying to figure out where to start. Because it’s so intermittent, it has me confused. I have not been able to recreate it with muffs.

 

[stresspoint]

take a look at the fuel tank breather or filler cap( some systems breath from the cap).
you guys are required to have an anti siphon system , that would also be worth taking a look at.

suck some fuel out from the bottom of the tank and check for water.

other than that : possibly a connector plug in the wiring has not been plugged in completely when work was done and is causing an intermittent bad connection.

 

[NotAGreatMechanic]

take a look at the fuel tank breather or filler cap( some systems breath from the cap).
you guys are required to have an anti siphon system , that would also be worth taking a look at.

suck some fuel out from the bottom of the tank and check for water.

other than that : possibly a connector plug in the wiring has not been plugged in completely when work was done and is causing an intermittent bad connection.

Thanks for the quick response!
Could that be related to fuel spitting out when I fill it up?
This is only our second boat. Slowly learning about them.

 

[palumanic]

it sounds like you're having some trouble with your SunTracker Party Deck 21. It's been stalling on you a few times, and it's driving you nuts because it's happening randomly. I get it, that can be frustrating. Here are a few things you could look into to figure out what's going on: Fuel issues: Sometimes stalling can happen if there's a problem with the fuel delivery. Check the fuel filter, fuel pump, and venting system for any clogs or issues. Make sure everything is clean and working properly. Ignition system: It's also possible that something's up with the ignition system. Check the spark plugs, ignition wires, and ignition coil to see if they're in good shape. If anything looks worn out or damaged, it might be causing the stalling. Carburetor: Since you mentioned getting a new carburetor, it's worth double-checking that it's adjusted correctly and functioning as it should. Sometimes even a small misadjustment or debris in the carburetor can mess things up. Make sure the fuel mixture is right and that all the carburetor parts are clean. Electrical connections: Loose or corroded electrical connections can mess with the power supply to the engine, which could cause stalling. Take a look at all the electrical connections, like the battery terminals, ground connections, and wiring. Make sure they're all tight and not covered in gunk. Propeller and hull: It's interesting that you noticed the waves affecting how the boat runs. Maybe there's something going on with the propeller or the hull. Check the propeller for any damage or debris that might be messing with its performance. Also, inspect the hull for any signs of damage or water getting in where it shouldn't.

 

[Scott06]

Thanks for the quick response!
Could that be related to fuel spitting out when I fill it up?
This is only our second boat. Slowly learning about them.

Yes if you have fuel spitting out when u fill up likely vent is plugged. Next time this happens open the fill cap and see if tank is under a vacuum. If it runs better with cap open then go clear the vent