Is the Fuel Manifold the Problem?

[Vincentc]

I thought I had the problem with the generator fixed; however both engines and the generator are now getting air and shutting down.

I had disassembled and cleaned the primary filters to removed the black alge.(Racor 1000's for the 671's and the 500 for the generator) and installed new elements. I also replaced the secondary filters for all 3 engines. When I primed the generator, the pump sucked air when the valve was switched to the fwd/midship tank, but not when I turned the valve to the aft tank.

We went for a boat ride this afternoon thinking everything was OK since I switched both sets of manifold valves back to the aft tank. Everything appeared to be fine for about 45 minutes running at about 1100 rpm, until while we were anchoring, the stb engine quit. I went into the ER, opened the top of the Racor and found that it's fuel level was low. I attempted to refil the Racor with the electric priming pump but it would not pump. I turned the valves on the manifold for the stbd engine to the fwd tank, and the pump would then fill the Racor. I loosened the bolt on the secondary filter (actually the 3rd filter, there are 2 after the Racor) and pumped fuel with the priming pump until it ran down the sides of the filter canister. The engine then cranked with little problem.

Later, while at anchor, the generator quit. The generator is paired with the port engine fuel valves. Like the stbd engine, the generator racor was low on fuel. When I attempted to fill it with the priming bulb in sucked air until I turned the port engine fuel manifold valves to the fwd tank. After turning the valves, the pump would then refill the Racor. I then used the electric priming pump on the generator and noticed that a small amount of air was visible entering the Racor bowl out of the turbine as the priming pump was running. After this, the generator cranked and ran fine, for about 30 minutes.

On the way home, everthing appeard to be fine, until we were almost home, after about 30 minutes running. This time the port engine shut down. Again, when I checked the Racor, it was low on fuel and the priming pump would not work until I turned the fuel manifold valves for the port engine to the fwd tank. Around this same time the generator had again shut down. I refilled the Racor, primed the engine and it started.

Since the engines suck air intermittently from both tanks, I appears the problem is with the fuel manifold valves. Any thoughts on how to correct this problem?

Thanks

 

[bobk]

I had a similar problem several years ago. I initially thought it was due to sludge blocking the pick up tube. I installed vacuum ages and found vacuum generally stayed low but would occasionally rise to the red zone. My Florida mechanic noted fuel weepage around the manifold valves and dissasembled them and refaced them (I think he did something like valve lapping) and at the same time replaced the hoses. The leaks are fixed, and I have not seen erratic high vacuum since, so our presumption is that there was a problem with the inner liner of one or more fuel hoses. Bottom line.... check/replace the hoses.

Bob
1981 48MY

 

[Vincentc]

Bob,
Thanks, we have plans for the boat this weekend and I need to fix the problem soon. Makes sense to repair the valves and replace the hoses. I might even add the Fleetguard spin on primary filter recommended by Tony Athens.

Does anyone know the details of getting to and repairing the valves?
I wonder what is involved in valve repairs and if it is more practical to replace than to repair the valves?

Regards,

 

[Vincentc]

After much pondering and pursuit of solutions, I can answer my question.
The Fuel Manifold is not exactly the problem.

When all else fails read the manual, do not assume and consider simple solutions to apparently complex problems. The manual has a print showing separate fuel lines from the aft tank to the manifold for the 671's and generator fuel lines which do not go to the manifold but go direct to the generator. Therefore, the generator draws and returns only to the aft tank.

When I turned the manifold valves to the forward tank I thought that switched to generator to the forward tank. I knew the aft tank was low, but thinking I was now drawing from the forward tank, didn't think that mattered and decided I had some complex problem with the fwd tank. All 3 Racors were loaded with gunk, and that coincided with rather than caused my manifold problem. The gunk may have ruined or imparied the fuel priming pumps, but I can prime and start the engines now that I have sufficient fuel in the aft tank.

Best I can tell, on the 43 DC you can only run the propulsion engines from the fwd tank, and cannot run the generator without sufficient fuel in the aft tank. Let me add, when you have a lot of people on board who enjoy riding on the bow, you should not try to run off of a tank with low fuel, since the fuel pickups are in the aft part of the tank and a bunch of adults on the bow will lift the stern.

I hesitate to broadcast my ignorance, but perhaps some of you can benefit from what I've learned.

Regards,

 

[sgharford]

Glad you shared. I remember YachsManWillie saying something about generator fuel pickups typically only extend about 2/3's way down tank so you do not inadvertently use all your fuel and have nothing to get home. That's why I read every post - never know what you are going to pick up along the way.

 

[sgharford]

Jeese Vincent - Deja Vu. Coming back from musical festival yesterday my port engine dropped 1000 RPM out of no where and started bouncing (ran about 4 hours that day no problems). All gauges looked normal so I dropped to 1000 rpm where port engine ran pretty steady and had my brother take the wheel while I went below with the ear muffs on and flashlight in hand. Nothing gushing (hurray!) and the fuel filter bowls looked good (Dahl 200's). Thinking I got something in port tank, so I flip the manifold over so port engine drawing from startboard tank and everything evens out. I could see big air bubble in fuel bowl as I switched over. Anyway, assuming somthing came loose between port manifold valve and port fuel pick-up which I'll have to delve into later this week. On my 1976 43 DC, I have port and starboard tanks under single berths in rear stateroom that feed each engine respectively (and reason fuel coolers a neccessity - keep your bed cool!). The generator has it's own pick-up in port tank.

I ran next hour home at 1400 rpm instead of 2400 rpm as I was not sure if copper fuel lines from starboard tank to manifold could handle twice the normal flow thru them. Anyone know if the good folks at Hatteras sized the copper fuel lines to and from the tank(s) twice as big for this occassion? My gut says yes.

 

[REBrueckner]

On my 1972 48 YF, I know I could run both engines from any of three tanks without any fuel issues. If your fuel manifold allows you to select either tank or both tanks, it's likely Hatteras provided adequate size fuel lines for proper operation. That applies to both supply and return lines.

From all prior discussions on this forum, it seems the gennny is generally supplied from one fixed tank without any selection options. On Hatts with dual gennys perhaps someone could post how the fuel supply and return options, if any, are plumbed.

 

[MikeP]

On an '80 53MY, the genny feeds ONLY from the FWD tank so if you run out of fuel in that tank, you have no genny capability. The position of the fuel manifold levers has no influence on the genny fuel feed/return.

 

[rsmith]

On an '80 53MY, the genny feeds ONLY from the FWD tank so if you run out of fuel in that tank, you have no genny capability. The position of the fuel manifold levers has no influence on the genny fuel feed/return.

mines the same way altho I have a 6.5kw backup genny that feeds from the mid. Mike is your fuel tank setup the same as the 50-53c? 3 tanks down the middle? 250 aft 350 mid 450 fwd? 275 h2o?
The main genny runs out of fuel leaving about 75 gal in the fwd tank and it is a PITA to reprime if it runs out.