Carver 400 MY engine RPM issue

[g36]

Yes the list or save for later if you move it out of your shopping cart. If I am watching something I will check back on amazon often sometimes more than once a day

[hausherrs]

Hey all,
I have some new developments to add to this thread.

The issue had come back so I went through and changed the throttle body filter and re cleaned the ufo filter. Took it out and tested it. Seemed fine that day.

I took it out again yesterday. Once I got out into the bay I throttled both engines up and the stbd pretty much fell on its face. When I would get it up to 2000 it would drop to 1000 rpm. It would bounce back and forth between 1000 and 2000. If I opened it up all the way it would drop to 500 rpm or less (200ish). Even in neutral it would not throttle up. It would just spike up and down, sputter, and act like its trying to die. After all that we dropped the anchor and fished. We didn’t catch anything. About an hour later we pulled the anchor and headed in. At that time the engine ran fine all the way back to the slip as if nothing ever happened.

I am thinking that this is fuel starvation. There is always quite a bit of junk in the ufo. I have never looked down in the fuel tank. Its nearly full at the moment with more than 3/4 tank of fuel in it. I have a bore scope I could use to get in there. I might consider that. But it almost acts like there is a bunch of junk in the bottom of the tank and it builds up at the pickup and eventually blocks the flow.

One other thing worth mentioning is when it was doing that the exhaust smelled like it was burning bad fuel. Maybe I had a water pocket hit the pickup.

To-Do list:
1) Bore Scope in tank. Clean tank if needed
2) Replace separator filter
3) Replace the check valve


Just curious if anyone has seen this before.
Thanks,

Steven

[cpoint]

Welcome to my problem
On my carver 356 had the problem since last year. After practically replacing all expensive parts, and emptying the tank 3 times (third time supposedly they cleaned up the tank), left tank empty during winter, started this season for an hour all good, second time out past 2000 RPM slight fluttering on tachometer. before going out next time, replaced the filter, all good for an hour and all good as long as under 2000 RPM all other times. So this weekend, replaced the filter and checked the fuel, yeap there is crap in the tank again. See attached picture. This is same brown stuff (dust like) was in tank last year that was supposed to be cleaned. So now I am not sure how its there again if it was cleaned. Anyone have any ideas where this would come from if tank was cleaned? Hate to dump all the fuel again, as it coast 700-800 each time to get the service out recycling the bad gas and getting new gas. Interested thing is every time I change filter, I am good for an hour at any speed, but if over 2000 RPM than starts moving around (tachometer) after 2000 RPM. Not too drastic but enough to make me uncomfortable.

[km1125]

I was doing some research for a friend with a similar issue on his 356. He has what looked like red rust particles in his filer and it would get bad enough that he could not run over 2000 RPM. He would change filters and be OK for a while but then got in the habit of taking the filter off and "reverse flushing it" to get most of the particles out, then he would reinstall it.

I ran across some info somewhere (and I'd have to search again to find it) that for several years Carver used fuel tanks with copper dip tubes. In an aluminum tank, the copper would begin to 'corrode' and shed these particles which would travel downstream into the filter. The solution would be to pull the dip tube and replace it with a plastic one. not sure if there was a recall on this, or just a service bulletin. i'll poke around and see if I can stumble on the site again, but I"d suggest searching for it or contacting Carver or the tank manufacturer and asking them if your tank would have been affected by that issue.

[cpoint]

km1125, thanks for the research. That's a possibility. I'll check into that. I just talk to another company to filter my tanks and clean this time (no extraction as there is no water issue), I think filtering will clear the tank, but need to find the source. What you are saying may be the issue, will definitely look into it.

[hausherrs]

When my problem first surfaced I checked the Oberg and there was quite a bit of black rubber beads in there. It had the Oberg screen about 40% blocked. I cleaned it and immediately took it out for a test. Easily ran all the way up to 4k. I thought that was the issue. Then the next time I took it out it ran good again until about the one our mark and the engine was gradually losing power. I took it back to the slip and checked the Oberg again. It was maybe 5% covered with the black beads. So I replaced the throttle body filter. I dumped it out and some blackish fuel came out. Nothing alarming. Last week I pulled the separator filter out. It wreaked of bad gas (Varnish). I dumped it but didn’t have a filter to replace it with. I have one now and might replace that today. The fuel in the tank is maybe 2-3 months old. The previous owner has a fuel leak in this tank before he sold it to me. It was fixed but the cause was from a rotting rubber gasket on one of the clean out ports dissolving because of the ethanol in the fuel. All gaskets were replaced with ethanol safe gaskets. I suspect that the black beads are from the old gasket, but who knows.

Mine seems to only do it after running for 45 minutes to an hour. Shut it off for 30 minutes and it acts like nothing ever happened. Strong all the way to 4000 rpm. I tried to get a bore scope down there to have a look but I couldn’t get it past the baffle. Mine is to be continued.

Oh and for what its worth this stbd fuel tank has a manufacture date of early 2000s. So its not the original.

[waybomb]

On our project boat that had been sitting 10 years, the starboard tank never cleaned up well. I always get a brown sand-like substance and there is some black gunk in there.

I've been fouling the Wix canister filter on that side regularly, as in twice a year no more fuel flow.

So, I bought two giant Racor separator/filters - the cartridge is a 10 micron S3232TUL.

Installed them this past weekend.

[Viper]

Source of the post.....Mine seems to only do it after running for 45 minutes to an hour. Shut it off for 30 minutes and it acts like nothing ever happened.....

This is typical of the tank pick up tube screen getting covered with debris while you're running. As long as the fuel pump is calling for fuel, the debris remains on the screen. After a while, it gets covered enough to affect performance. When the engine is shut off and there's no more vacuum, the debris falls away and the engine runs fine for a while until the screen clogs up and starts the cycle over again.

While the screen is the first line of defense (not all tank pick ups have them), under these circumstances, they can be a pain. Most guys with contaminated tanks simply remove the screens and rely on primary filters to do the job so they can get longer run times between engine failures due to the debris in the tank.

The other thing that causes the same symptom is the tank not venting properly. This prevents atmospheric equalization, eventually creating enough of a vacuum in the tank to overcome the pump's ability to extract fuel after running for a while. Once the engine is shut off, the tank eventually equalizes and the engine will run again until the above conditions prevent it once more. To check if this is the problem, remove your gas cap and take it for a run. If nothing happens, you likely have a restricted vent line or fitting.

[hausherrs]

Viper,
My 63 year old mother was on the boat when this happened. She told me a story about her beetle having so much rust in the tank that it would gather around the pickup until the car wouldn’t run. Let it sit and it starts right back up. I vaguely remember that car so it had to be 1981 or so.

The last time I filled up the kid overfilled the tank and it spit a little fuel out the vent. It didn’t appear to have any blockage. I’m betting there’s junk in there but my tanks are 90% full. And I don’t want to call the $1000 man out to work on it.

Ill pull the access panel off today and see if I can get to the pickup.

Thanks

Steven

[mjk1040]

Damn ethanol raises hell with everything. Eats up all the rubber parts, draws moisture twice as fast as the old fuel and it has been strongly suggested not to store it for more than 30 days as it breaks down and almost separates, then goes south on ya.