Carver 400 MY engine RPM issue

[Viper]

The problem with adding more filters is that you create more restriction which can lead to vapour lock. It may not happen due to temps alone but it might happen from increased vacuum in combination with normal engine bay temps. More filters, fittings, bends, fuel line, etc. will all contribute to getting the vacuum to a place where it becomes a problem. To complicate things, you may then end up with a completely different issue that you'll likely think is due to something other than the fuel system because you then assume you've corrected that problem with additional filters.

[g36]

i thought those racor 500s are diesel only. 10micron? do you need such ahead of the other fuel filters? i have the same black stuff and i just swap obergs with cleaned screens.
theres 3 options for the oberg micron. although the smallest oberg is 28 micron i would think with the ease of filter swaps you could carry a extra set of screens and then replace when neccessay and then reclean the dirty and then have them ready when needed again which is my approach.

[hausherrs]

Qr Bbpost racor 500s are diesel only. 10micron? do you need such ahead of the other fuel filters?

Nope the 500mam is Gas and Diesel. I got the ma and bought a mam (metal bowl conversion kit) for when I get most of the stuff out of the tank.

For now I am using 2 micron. Once the trash level drops ill go to 10 micron. But Ill probably be changing the 2 micron every week for the next month or so.

[hausherrs]

Qr Bbpost adding more filters is that you create more restriction which can lead to vapour lock

I had vapor lock issues before the racor. Not bad. Just start the engine with 10% throttle. But the way these fuel pumps operate they do not prime well at all. I replaced the oberg with the racor. Added about a foot of fuel line and the swapped filters. And went from non running engines to running engines. I found a vapor lock kit. Its basically a pump that primes. But thats $400+ per engine.

Thanks for the input, ill keep that in mind.

[390Express]

Qr Bbpost The problem with adding more filters is that you create more restriction which can lead to vapour lock. It may not happen due to temps alone but it might happen from increased vacuum in combination with normal engine bay temps. More filters, fittings, bends, fuel line, etc. will all contribute to getting the vacuum to a place where it becomes a problem. To complicate things, you may then end up with a completely different issue that you'll likely think is due to something other than the fuel system because you then assume you've corrected that problem with additional filters.

My initial plan was to go back to the Oberg fuel filter alone, once I got rid of my fuel filtration issues, but I think I'm going to scrap the Oberg setup all together, and go with the can style filter. It's a better filter, with more surface area, and helps pull more sediment and water out of the system. After 6 hours of running I had zero water/ethanol separation in my last filter swap. I'm fairly confident that my Ethanol separation issue is done, but I still have a fair amount of sediment in my tank. After the same 6 hour period, a fair amount of crud came out of the filter. The only real advantage I see with the Oberg, is you get to see what was in your tank. If the boat is running right, I really don't care. It's like being able to see a colonoscopy of a dead cow I'm about to eat... It's not like an oil filter, where it could point me to a diagnosing a long-term issue. As long as the boat is running, I'm good with not being able to (easily) see the inside of the filter.

I'll try to update pics when I get a minute, just trying to finish up some last minute boat issues, before I have to pull it. We only have a couple more weeks of boating left in the season up here. I am having a bit of a hard time maintaining 3k+ rpms. For the time being, I'm attributing it to the dual filter, and lower octane fuel, given that about 1/2 of the prior fuel in the tanks had ethanol separation. The ethanol and water is gone, but it leaves behind lower octane gas. It's only 40 gallons max, I'll add another 20 gallons of 91 this weekend, and see what happens. After this weekend I will also pull one of the filters to see how she runs, going back to a one filter setup. I'll post those results as well.

I plan on authoring a complete ethanol separation/bad gas thread for future reference. At this point, I've done a shitload of research on the subject, and although my issue should be resolved, I think others would find it worthwhile.

[Bentone23]

Thank you for teaching me about my fuel system. I wondered what that pancake thing was. I will clean those next trip to the boat. Hopefully this will solve the 10 psi fuel pressure to the port engine. My Carver 355 1996 vintage has a generator. Where in the fuel system does it take fuel?

[Viper]

If I'm not mistaken, the generator draws from the port tank. A 355 owner might chime in and confirm.

[tomschauer]

My 1998 355 generator draws from the prot tank with no option to change tanks.

[tomschauer]

Port tank. Apparently, my keyboard has dyslexia.

[cpoint]

my 2000 356 aft cabin takes it from port or aux depending on switch, but definitely not from star board. I think 355 and 356 are very similar.