Thunderbolt 5.0 keeps dying

[amplay]

You guys are being so helpful !!
I fixed the jumper on the OP sensor, it was not done well. I then put a meter on the wires for the Fuel Pump, and had 12V continuously. Then I tried pumping the fuel into a bucket, and that worked without stopping. I then put all back together, and started the engine. It ran at 1500 RPM for ~ 30 seconds and just died (as usual). So I'm thinking a bad fuel pump, unless one of you has a different suggestion. I was unsuccessful loosening either the top or bottom bolt to the pump, as they are too tight. I sprayed WD40 and will try again tomorrow. Thanks .

 

[alldodge]

Might be the OP switch
Jump the switch (connecting both wires together) and start the motor to see if it continues to run. The pump will turn ON when key is turned ON.

If this works its the switch

 

[nola mike]

guys are being so helpful !!

I fixed the jumper on the OP sensor, it was not done well. I then put a meter on the wires for the Fuel Pump, and had 12V continuously. Then I tried pumping the fuel into a bucket, and that worked without stopping. I then put all back together, and started the engine. It ran at 1500 RPM for ~ 30 seconds and just died (as usual). So I'm thinking a bad fuel pump, unless one of you has a different suggestion. I was unsuccessful loosening either the top or bottom bolt to the pump, as they are too tight. I sprayed WD40 and will try again tomorrow. Thanks .

Did you still have 12v at the pump when it died?

 

[amplay]

I replaced the fuel pump, and I thought I had everything fixed. Boat ran for about 2 hours, mostly in idle while I was trolling. When I was done I powered up and the engine died, and I had trouble restarting. I also smelled a little gas. I could not find a fuel leak, so I'm wondering if the carburetor got flooded. Do I need to re-adjust the carburetor with the new fuel pump? Once I got it restarted, it ran at 2000 RPM all the way home.

 

[Scott06]

I replaced the fuel pump, and I thought I had everything fixed. Boat ran for about 2 hours, mostly in idle while I was trolling. When I was done I powered up and the engine died, and I had trouble restarting. I also smelled a little gas. I could not find a fuel leak, so I'm wondering if the carburetor got flooded. Do I need to re-adjust the carburetor with the new fuel pump? Once I got it restarted, it ran at 2000 RPM all the way home.

May have been flooded. I often get that with my eldebrock carb and advancing the throttle helps clear the flooded situation as it dribbles fuel when stopped.

You may want to also look at a carb rebuild you may have had a situation where your needle and seat is getting hung up. If it happens again look down the carb and see if float bowl is overflowing or if booster is dripping fuel at idle

 

[tank1949]

I have a 1998 Mercruiser Model 5.0L (2-BBL) 1998-95 GM 5.0L - 305ci - 8cyl; S/N OL045552

Rebuilt carburetor in the spring, and engine ran well. Now about 50 running hours later having a few problems. First the engine died going from 2500 RPM to Idle. Then the engine died on throttle up, and throttle down. Then I would have trouble starting, then no starting. I jumped the Oil Pressure Sensor, and engine starts every time, but dies after about 10 seconds. I have replaced the Coil, Distributor Cap, Rotor (all were original, so ready to replace) but no change. I disconnected the gas line going to the carburetor, and gas immediately leaked out, so I don’t suspect a fuel issue. Not sure if this is related, but I have a (slightly) wondering tach.

Purchase a new Edelbrock with electric choke.

 

[alldodge]

Might just be a speck of crud in the needle seat. Get it started and see if you see fuel dripping at idle or when its shut off

 

[amplay]

After reading this page in my owners manual, I think I'm going to switch the Needle Valve as shown. Has anyone had success with that before?

 

[stresspoint]

hot wire the fuel pump and check it , sounds like its dead ,

 

[alldodge]

The spring loaded needles can be an issue with flooding

 

[isaacs]

Have you ever replaced the ignition pick-up in the distributor? If you still have the old two wire "open" style (you can see the little circuit board) replace it. You may still be getting a weak undependable spark which is just enough to trigger your timing light but not enough to ignite your fuel. Don't buy aftermarket (Sierra), get Mercruiser or Quicksilver.

 

[amplay]

The spring loaded needles can be an issue with flooding

The picture below shows 3 parts in the kit. I have ordered the Mercury Quicksilver OEM Fix Kit Part# 3302-9407 3 times, and it always comes with just the part on the right. Does anyone have experience with this?

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[alldodge]

The ebay link isn't working but did look on ebay for 3302-9407 and several showed up shows pics of all 3 parts, where others that didn't show any parts

Merc part shows same but cost more.
https://www.mercruiserparts.com/9407-fix-kit
Might contact Mike's carbs and I'm sure they have what you need for less

 

[amplay]

I got 2 shipments from ebay with pictures of all 3 parts, one 1 from Wholesale Marine. All came in Quicksilver sealed bags with the 3302-9407 stamped on the bag, but just 1 part inside. I am thinking either Mercury changed the kit to 1 part, or the factory in China errored in packaging. Has anyone change to this setup, and are all 3 parts required?

 

[alldodge]

Merc Tech support
920-929-5040

 

[Scott06]

I got 2 shipments from ebay with pictures of all 3 parts, one 1 from Wholesale Marine. All came in Quicksilver sealed bags with the 3302-9407 stamped on the bag, but just 1 part inside. I am thinking either Mercury changed the kit to 1 part, or the factory in China errored in packaging. Has anyone change to this setup, and are all 3 parts required?

There is an error in packaging or counterfeit part.

The needle and seat always comes together as a matched set regardless of weather it is a spring loaded needle and seat or not. Contact who you bought them from and return them.

Also make note since the spring loaded needle and seat was a running change to help flooding issues at idle - there are different float level specs for spring loaded vs non spring loaded.

Also would recommend Mikes carb parts as a supplier

 

[amplay]

I went to change the Needle Valve today, and found that it already had the "non-spring" style. Any other suggestions as to why my carburetor is flooding? (I changed my fuel pump recently).

 

[alldodge]

Float level is set to high or pressure is to high

 

[amplay]

Are those adjustable?

 

[alldodge]

Are those adjustable?

Yes
Float level is done by adjusting the float tang

The fuel pressure is adjusted by a regulator if needed