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Cruiser
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Hi all.

My sailboat has a Westerbeke 42B4 diesel engine.
It starts normally, and can run for hours at cruising speed. Later, when I need to wait for as bridge opening, I would witch between neutral and idle speed for some time. Then, when bridge opens, I would press ahead, but the RPMs wild slowly drop and engine stops. Even at full throttle. Sometimes RPM would fluctuate without giving full power.
Restarting the engine sometime fixes the problem temporarily, until the next bridge...
Very frustrating. :confused:

More info:
- In neutral, the RPMs are holding fine, the problem is when engine is engaged.
- Fuel filters are freshly replaced and clean
- Tightened all fuel line clamps, etc. - fuel and air leaks are unlikely.
- Prop is clean

Any suggestions will be greatly appreciated.

Thanks.
 

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check the governor and lift pump filter (side of engine)....either can cause what you are experiencing. If you have changed the lift pump filter, then I would suspect the lift pump itself.

best of luck
 

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What about trannie fluid. If low sometimes it can't decide which gear it's in . Borg Warner for example can do both f and r and jam up everything till it cools off. More likely a fuel issue though.
 

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Maybe check around your filters and check to see they are tight enough may just need tightning up,sounds like a fuel starvation issue or air is slowly seeping in as you idle.Also check your bleed screws and water trap screws on your filter,these sometimes can slowly let air in.Good luck.
 

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argalax :

It sounds like you are drawing air, or perhaps you fuel lift pump is getting tired.
If you can, rig up a temporary gravity-fed fuel supply. Put your fuel in a glass bottle so you are sure that it is very clean indeed, and rig up a wee funnel feeding directly in to your injection pump (not the lift pump).
Tether your boat well at the dock. Do not go out in to open water. Start you motor and simulate your conditions that led to the problem.
If your problem goes away, then it looks like you are drawing air.
Have a close look at the lines when the temporary fuel supply is rigged. Is diesel weeping out? It is a good way to detect and fix leaks.
My old Volvo fuel lines used to draw air. I fitted a Stewart-Warner pressure pump (about 5 psi) that pressurises the fuel system about 4 ft from the tank line, and pressurises the filter and the lines to the motor.

This is a similar model....

http://www.ebay.com/itm/Stewart-Warner-Electric-Fuel-Pump-43-GPH-7-PSI-82091-/191328051425

I have never had a problem since.
I accept the added fire risk that comes from a pressurised fuel system, but I traded that risk against losing power from drawing air. I have very good access to my engine when it is running and I am constantly checking the systems. When the engine is running, I can place my hand on the electrical fuel pump and I can feel the intermittent "thrum-thrum" when it pumps.

Let us know how you get on.
.
 

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More info:

- Fuel filters are freshly replaced and clean

Any suggestions will be greatly appreciated.
• Re-install the fuel filters, and be sure to lubricate the o-rings and gaskets with fuel oil. You may have pinched an O-ring or gasket in the previous change-out -- very common, especially if you re-used the O-rings or Gaskets.
Always use new O-rings and Gaskets when changing the filters, as the previously used gaskets/rings will/can often 'swell and soften' in fuel oil service and the now larger dimensions due to 'swelling' makes them harder to fit correctly into the O-ring grooves, etc. This swelling is especially found 'blends' of diesel fuel that contain 'bio-fuels' / reclaimed cooking oils - sometimes added by private and dishonest distributors to illicitly to 'stretch' the fuel and where 'oleic acid' in the 'bio-fuel' is not removed. If you are indeed using so-called 'bio-fuels', then you MUST change out all gaskets or O-rings (and 'rubber' hose) to Viton® 'rubber' (expensive).

• If you removed any 'compression' or 'flared' fitting during the filter changeout, go back and visualize the compression 'nut' for a small hairline crack. If your system uses 'compression fittings', check the ferrule on the copper tube for 'tightness' - if loose, trim off a wee bit of copper tube at the end and reinstall the ferrule.

• check for partial blockage (fungus 'wads', etc.) in the fuel line, etc. -- Run the engine then return to a dock, etc. and long term idle until stalled, etc. When stalled, then open the fuel delivery system in sequence/series starting from the engine mounted guard filter, going back to the fuel tank ... looking for trapped air. The leak affected zone thats causing the leak will be the last section you open - then narrow down the cause - pin hole in copper tube, cracked compression fitting, pinched O-ring/gasket, blocked screen (small strainer) on the dip tube end, etc.

Consider to install a vac/press. gage on each filter (good to know WHEN to change-out) ..... and to be able to monitor for AIR LEAKS and blockages in future via vacuum 'hold' testing.
 

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I had a similar experience. Engine would run all day if needed and then when I would throttle back for what ever reason engine would slow and stall. Very inconvenient when approaching a dock. Problem was a dirty tank. Crap would slosh forward and block the fuel pickup. cleaned the tank and THAT problem went away.
 

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Closet Powerboater
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I had the exact same thing happen once when idling for a long time waiting for a current through a narrows. Throttled up to go and the engine died. Restarted and no issue. My tank was clean though as I had polished it myself. Engine was a Perkins 4-108 with a Borg Warner transmission.

Never had the issue again with years of boating and motoring. I'll be curious what you find.
 

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al brazzi
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I had a similar issue with my motor hunting for idle and stalling just as we came into the wind to anchor after some pretty heavy seas earlier in the day. I just knew it was a filter issue but turns out the vent screw on the Racor had come loose, a couple of unrelated hoses on each side of that knob twisted the vent screw loose, it would run fine above at higher RPMs with the pump moving lots of fuel back through the return line and only showed at idle where the pump couldn't overcome the air leak. Suction leaks are tough to diagnose sometimes and don't always show as leaks right away at least. If your tank is fitted with a supply check valve some Vacuum will be needed to open the valve creating more resistance to flow and can create a leak that you cant see with the system at rest. Maybe this will help.
 

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A diesel surging is telling you it's starving for fuel.
Had a similar problem on our previous 36t when the fuel tank was about 1/2 full. Finally figured out a filter gasket wasn't seated properly and would suck air when the fuel in the tank level was below the filter.
Pay attention to you fuel level when the problem starts happening and then start looking at fuel connections before the hp fuel pump above that fuel level.
Jim
 

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Lance...

Does that stewart-warner pump self prime? And if so will it prime with let's say a 2 ft elevation? Thanks for posting.

It will lift a 2 ft head of diesel without a problem. Mine has to lift about 3 feet. I built it on to a wee fuel platform together with the filter (an old Racor, still doing OK). I have the pump on an on/off switch. Some owners wire it directly in to the ignition, but I like to be able to switch the pump on and off when priming, and priming is rare, really.

Yes, it does self prime. It sort of chatters a wee bit until it reaches its 5 psi pressure delivery, then stops. With the engine running, it does a wee chatter about every 5 seconds or so. It's a good unit, and not too expensive. There is an added fire risk with it, but air cannot get in to the high pressure side.... only fuel can come out. I trade the starting reliability against the added fire risk.

If you forget to switch it off, it gives a wee single chatter about every half hour to remind you.

There is a wee in-built by-pass facility on it if you forget to switch it on. The Volvo engine-mounted lift pump can still deliver, at least in my experience.

I operate the engine room with the starboard access sliding hatches open all the time. It encourages me to keep checking on the old Volvo, now 37 years old. I have never been at ease with an engine shut-in behind panels.

Rockter.
 
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