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Got Towed in, Indmar Carb 310hp lost fuel pressure, need help troubleshooting

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We were out on the river last week in our 98 Sunsetter, and as we were crusing, the motor started to lose power quickly, then completely died within 30 seconds. I opened the hatch and tried to start a many times over the next 30 minutes, but nothing.

It felt like the fuel pump stopped working, so I took off the flame arrestor, and pumped the throttle a few times. I did not see any fuel squirting in the carb, so that comfirmed my thought that the motor wasn't getting fuel. I initially thought I lost the fuel pump

Next, I started to mess with the safety lanyard switch because I thought that would cut power to the fuel pump. I checked the wire connections, and played around with the switch to try to make sure that wasn't the issue. The only thing I didn't do, but should have, was jump the two connectors to bypass the switch.

That was all I could think of while I was out on the water. After we got home, I got on this site as started to check on the possible problems. After reading the threads, It seemed like the three most likely issues could be the safety switch, the oil pressure sending switch, or the fuel pump.

I went out to the boat later that night to troubleshoot, and wouldn't you know it, it fired right up. So now I'm not sure how to trouble shoot the issue.

This makes we think it was the oil pressure sending switch. Is there anything else on this motor that would cause the fuel pump to stop getting power?

FYI, I did a tune up at the beginning of the season with cap/rotor, plugs, and fuel filter

Thanks in advance for the help.

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Carbed engines rarely have an electric fuel pump, should be a mechanical unit. There is no fuel cutoff system on a mechanical pump / carbed setup so it would not stop fuel supply electrically in that case. Vapor lock sounds like the more probable cause. The ignition side is a different story and could have an issue where it cuts out.

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Mine does have an electric fuel pump, here is the model that is available on Ski-Dim. Not sure why or when they changed to the electric version. The reason I didn't think Vapor lock, was that it died as I was under way at 2500 rpm. I thought that Vapor lock normally happened after the engine was turned off, then not able to be restarted because of vapor in the fuel lines. Also, I didn't think the carbed motors had issues with vapor lock because of the low fuel pressure

http://www.skidim.com/prodinfo.asp?number=RA080018 - I can follow my fuel line directly from the tank into this pump sitting on the side of the engine.

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So this pump actually sits next to the engine (I assume where the old mechanical one used to be (right side or behind the drivers seat near the front of the block just above the pan rail). Could the pump be getting hot and not pumping but the carb / residual pressure can empty the water separator until it runs out, I would think that might take about the distance you mention. If you have one of those cheap pyrometers' from Harbor Freight you could shoot the pump & other parts when the problem reoccurs. I would also consider getting some clips and wires to jump the pump when it happens again, although you should be able to listen to the pump to see if its at least trying.

Yes vapor lock normally boils the fuel that's in the rail or lines on top of the engine that are hottest, so your theory has merit. If it's like an off/on switch I would do some electron diagnosis (which can certainly be a PIA). Good luck.

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Yes, you are correct, it is in the same place as an mechanical pump in the carbed engines. It felt like the pump stopped working, then it slowly started to lose power and rpm's until all of the fuel was out of the lines and bowls.

Another note, I have owned this boat for 6 years, and I have never had an issue with vapor lock, even on days much hotter than this. That is why I keep going back to a switch that is shutting off power to the fuel pump.

I was trying to get an idea about what switches would stop power to the fuel pump. I searched previous threads and found the following could cut power to the pump:

1. oil pressure sending switch

2. safety lanyard

3. Is there some sort of fuel pump relay?

4. I saw a fuel pressure sending switch on ski-dim, not sure if this could be an issue

I am going to try and reproduce this in the driveway, but I'm not too confident (what are the chances that would happen?)

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