460 idles fine, backfires and dies when trying to plane out

[shmuck2002]

Hi all,
Here's my setup:
Ford 460, Bassett short tube water injected, berkeley jet. Holley red fuel pump w/ regulator set at 4.5 psi.
Quick history on the problem:
Boat ran great for a full season, then I had a mishap with a bad fuel cap seal and got water in one of the tanks. Discovered the water issue while out on the water Drained and flushed both tanks and the whole fuel system, fixed the bad fuel cap seal, and we were good to go for a long weekend at the lake, ran about 5+ hours without a hitch. Next time out, ran well for about 45 minutes, then started having a problem with it running strong for about 90 seconds, then would stall. Would not start up again for about 3 minutes, then would repeat the same pattern (as we're desperately trying to get back to the launch from the furthest point on the lake!!).
I had thought I ended up with water in the fuel again, so I pulled the fuel line off the carb and ran it into a clear container, where I would see the water collecting on the bottom, however no water this time. Went ahead and completely flushed out the fuel system again, and out for another test.
This time, it's even worse: idles just fine, no missing, and when i get out past the no wake zone and start to plane it out, it backfires, and dies. Turned around and idled it right back to the dock.
so i guess my question is... HELP!!!

[nova1]

Just an thought. I had a 460 in a jet boat for 10 years. Start boat out side water with hose or back trailer into lake (best) . Start and idle. I always had my regulator set at 6.5 psi for a 4bbll carb. Check your carb spec by calling Holley.
You should be able to have someone run motor up and you view the fuel sight glass to make sure fuel is at the right levels. And watck your fuel pressure, it should stay the same.
This may show you a little whats happening, You may be running low on fuel when you step on the gas.
Also, slim chance, you may still have some water laying in the bowls.
I know technology is king but I still like the mech. fuel pumps.
I have seen many strange things happen to MSD boxes and ign. systems when your voltage drops below 9v-10v for some reason.

[HOSS]

4.5 is too low, I`d be like said at 7. I too think your running out of fuel in boals. As said, check site glass. Another thought. Sure you dont have bent valves or broken exhaust valve spring(s)?

[shmuck2002]

Hey guys, thanks for the replies! I am running an Edelbrock 1409 (600cfm) carb, and I have the original manual for it, so I will verify recommended fuel pressure, and the float window. Also will drain the bowls to check for water. Sounds like a run to the "test lake" for me this weekend!! Will post results soon

[justfloatn]

There is still water in the carb somewhere. Draining the bowls will still leave a drop or two in there in a passage or corner of the bowl and that is all it takes. You will need to dissassemble the carb and spray it out with brake cleaner.

[shmuck2002]

Thanks JustFloatin, I am suspecting water as well, since that was the root cause of my initial problems.
PS, love that avatar!!

[Wet Dream]

Take the carb off, remove top, turn upside down and squirt every hole with cleaner until it comes out somewhere else. Remove jets too.

[shmuck2002]

Hey guys,
I finally got time to work on the boat this weekend. I pulled the carb, pulled it apart and drained the bowls (no water, clean fuel), and blew out all ports. The only place I found any gunk was the pump jet sprayers. Cleaned them out carefully and made sure they were both spraying smoothly.
Hooked the boat up to the garden hose, she runs fine, and up about 4000 rpm, she starts doing small backfires. Holding the throttle in that range, it doesn't stall and RPM doesn't fall, but the mini backfires remain constant. letting off the throttle hard or soft, it does not stall, idles quite well.
What do you suggest at this point?

[H20MOFO]

I hated my edlebrock carb. Every spring it would start and run but just sickly. It may or may not be your issue, but like wet dream said take it apart and spray every hole out. I know you already did that, I had to use a compressor and some serious psi. Wear glasses, the last chunk of crap I blasted out of there missed my eye by a centimeter. I'm certain carb cleaner wouldn't have touched it. If you know someone you can borrow another carb from that would be a bonus.....maybe you just need a tune up....but what you describing sounds exactly like my 1st trip out every spring.

[shmuck2002]

Thanks H2O, i'll pop the carb and go at it with the compressor (and safety glasses!). Any other suggestions out there from the masses? possible timing issue? plugs?
I pulled each plug yesterday to inspect, most were light brown in color, and a couple were black. From the previous owner and the shop notes, it uses "25" plugs, which I presume is a gapping reference.
Just trying to cover all my bases here. My fear is, although it runs "pretty good" on the hose, I'm going to get it out to the lake to test, and find that under load, it does the exact same thing it did the last time it was in the water. either way, even if it runs the same on the water as it is on the hose, I am not satisfied with the backfiring it is doing.
PS - from reading in other threads, this seemed to be important: it is backfiring thru the exhaust, NOT back thru the carb.