Runs for ~30 seconds then dies (04' Mobius 310 Indmar Carb)

[smokeysevin]

Hey guys I have a new issue in the 04' Mobius, the motor is an Indmar 310 assault carb with the stock Holley 4150 on it. When we got the boat with 318 hours on it I noticed that the top speed was slower than it should have been topping out around 35. I attributed this to the ballast bags filling up on their own and put it out of my mind. Since then the bags have been fixed and the top speed has been down still.

I took the boat out last week and it died several times, when it died it took me priming the carb by pumping the accelerator to get it to fire back up. When it died the first few times it would run for several minutes and eventually ran well enough to ride for the afternoon. While running it there was a slight hesitation on takeoff a few times but it quickly woke up.

I shut the boat down and had dinner on the water and after about an hour went back to bring it home and it was at this point that the motor would only run for roughly 30 seconds then die and only restart after pumping the accelerator. This tells me that it is a fuel supply issue.

Based on the symptoms and some quick searching, am I right in replacing the fuel pressure safety switch, oil pressure switch, fuel filter, and fuel pump for peace of mind? I am not a fan of carbs in general but since the cost of replacing the carb with EFI on the stock motor is prohibitive and offers little power gains, is there anything I can do on the stock motor for the next few seasons until I can justify a 6.0 LS swap or similar?

If this all makes sense, where is the best place to order parts from? I need to have the boat up and running by this weekend.

Sean

[parrothd]

Skidim.com and check that the choke is working. Should be fully open, sometimes the wire on the side to it comes off... If replacing that stuff doesn't help I'd rebuild the carb or have someone do it., you can also buy a new one from skidim. The carb rebuild kit from holley is around $100?.. I think.

[smokeysevin]

Skidim.com and check that the choke is working. Should be fully open, sometimes the wire on the side to it comes off... If replacing that stuff doesn't help I'd rebuild the carb or have someone do it., you can also buy a new one from skidim. The carb rebuild kit from holley is around $100?.. I think.

I have really been eyeing the edelbrock 1409 or 1410 with the edelbrock replacement manifold as a replacement for the stock holley, they seem to have good reviews.

I am betting the carb needs a rebuild anyways

Sean

[parrothd]

The choke should be closed when cold and and open when hot. Try bypassing the oil pressure safety switch and see if that helps.

[smokeysevin]

I am assuming that the oil pressure safety switch is normally open and goes closed when it gets pressure, is that correct?

Sean

[parrothd]

Yep.. Jump the wires together, but don't leave it that way when not running, the fuel pump will run constantly..

[smokeysevin]

Easy enough, I ordered a new fuel pump, pressure switch, spark plugs, and fresh water flush kit (unrelated to the issue)

do you know what the part number is for the fuel filter?

Thanks,

Sean

[smokeysevin]

Shotgun approach worked, the boat runs fine now. I think the carb needs a rebuild as well because it can be hard to start after sitting for more than an hour or so but otherwise its great now.

Sean

[parrothd]

Mine does that, are you giving it throttle when starting? I generally don't shut it off.. :)

I give mine a good pump(accelerator squirts fuel) then leave it near 3/4 wide open when starting...

[smokeysevin]

Typically I give the throttle 3 pumps then it will fire. I am just spoiled coming from the efi world.

Sean

[smokeysevin]

Where is the filter and water separator located on these boats? The LS started struggling again last night. I did find a slight exhaust leak which I am sure partially contributed to the issue as well.

Sean