cleaning fuel tanks

[dogon dory]

Sorry, Folks - Post Deleted By Author

[dogon dory]

Sorry, Folks - Post Deleted By Author

[Larry H]

Here is another possibility,

If a carb is too lean at idle the motor will not accelerate properly.

I looked at a Honda carb expanded parts view for a Honda 40/50 and there is NO accelerator pump. I think the Honda 90 carb is similar.

Too lean at idle can be caused by partial obstruction of the idle circuits, or obstruction of the idle circuit only on one or two carbs.

To check for air leaks into the fuel system while running the motor, substitute a clear hose for the rubber hose between the primer bulb and the motor. Watch the clear hose while running the motor. A few very tiny bubbles are ok, but large bubbles are an indicator of an air leak into the system. It is possible for air to be drawn into the fuel system without gas leaking back out. Be sure to remove the clear hose after testing!

I have also experienced poor running after taking on fuel at fuel docks. Fuel docks don't sell as much gas as land stations, and if their fuel is old, the octane may have declined. Also the ethanol in modern gas attracts water and the ethanol/water mix is a poor fuel.

[Almas Only]

Thanks for feedback and suggestions on possible causes.

Rick: I’ll check credit card receipts, logbook, etc., and get some info on where I took on fuel, and began noticing the problem on our cruise. Maybe we can figure something out.

Joe: I don’t think the fuel selector switch is causing the problems I’m experiencing, but I’ll be sure to make some specific notes on this possible cause the next time I’m on the water (hopefully, soon!). Although the primer bulb can cause lots of problems, I don’t think that’s the case here. Mine does face the right direction (almost put it in backwards, but managed to see that big, old arrow). A failed anti-siphon valve should allow the fuel to flow from the bowls, back into the tanks, when the motor is turned off. That would result in hard start problems. However, once the motor is up and running, the fuel pumps are sucking fuel from the tank, and the anti-siphon valve doesn’t do anything, other than present a slight impediment to the flow of fuel from the tanks, to the motor. Seems like once the motor is running, the primer bulb is the functional equivalent of a bulge in the fuel line.

Vern: I’m wondering whether you also got hesitation when you tried to power up, or if the motor just quit running and wouldn’t start, as if it were out of fuel? I think I’m going to take along a portable tank of fuel I know to be good, and do some more experiments to see it I can pin this down a little better.

david

[Larry H]

Anti-syphon valves,

Anti-syphon valves are not required if all of the fuel system hoses are above the top of the tank.

An anti-syphon valve is a check valve which has a ball and spring inside. The ball is held onto the seat by the spring and is pulled open by the vacuum provided by the fuel pump.

If the ball is steel, it can rust from ethanol/water in the fuel system causing it to stick in the closed position. Varnish deposits from old gas can do the same thing.

The primer bulb has to be soft enough to squeeze, however if the bulb is too soft, it can collapse under vacuum and not let the anti-syphon valve open(as per Dans post). An air leak into the fuel system can cause the same thing. Primer bulbs can become soft due to age or components of the gas like alcohol.

If the anti-syphon valve is removed and any of the hoses dip or are routed below the top of the tanks, a leak in the hose at the low spot can cause gas to syphon from the tanks into the boat.

[dogon dory]

Sorry, Folks - Post Deleted By Author

[BrentB]

Would a bad vent hose or vent cause this problem?

[Holoholo]

My motors would die as I powered up, so we figured there was some kind of vaccum leak because the carbs were adjusted to factory specs. After draining the tanks and examining the pickups, they crumbled like potato chips and since the bottom screens were broken off, you could surmise that the small fragments could easily be sucked into the fuel lines. Also, since we don't know how much of the one pickup was broken off from the top of the starboard tank, this could also have affected the acceleration problem when the boat and tank and fuel shifts on acceration. Plus, after changing the primer bulbs, I noticed that they would now prime hard before starting both motors. And finally, when I changed to both new Yamaha fuel connectors, they would engage where you would feel and hear the snap when plugging them in, thus giving me the confidence that there were no air or fuel leaks. I purchased my boat back in October and the prior owner had not given it much use and although the motors had only 100 hrs each, I would have been far better off to have first checked the tanks and changed the hoses, fittings and filter. Anyone who has plastic pickups, should definitely change them out right away!

Hope this helps.

Vern

[blackfish]

In reading some of the latest posts it would seem there is a problem with the fuel pickups in boats around the same age as mine
so I think I'll be removing mine for inspection.
back in nov not long after buying the cd I tried removing the fuel tanks with not much success. I was unable to get the large fill tube off the top of the tank it almost seemed like it glued onto the post. Has anyone else had this problem?
I should have time next weekend to give another go, I was thinking about cutting the intake line but then I'm left with problem of replacing it.

if some how I manage to get the tanks out how would I go about removing the fuel pickups?

[BrentB]

Where do you purchase parts?

[Holoholo]

I found the easiest way to remove tanks is to first siphon as much gas as possible. Remove both starboard front covers. Then take some silicon spray with a tube and spray lightly between the connection of the black fuel hose to the male fuel tank inlet after removing the clamps. Do this for both the fuel and air lines. Then tilt up the section of the tank closest to the center of the boat and twist gently until you free up the fuel and air lines. Once you free the lines, get a pry bar and gently pry both hoses off, they should come off fairly easily and then the tanks will easily slip over the starboard tank strips. My mechanic ordered the pickups but I believe you should be able to easily find them at most online marine stores. If your pickup has disintegrated (like mine did), after you get all the large pieces out, take some air and blow it dry. I then took a shop vac and put a smaller hose taped to the main hose and sucked any small remaining particles in the tanks.

Vern

[Sea Wolf]

Next question:

When reinstalling the pick up tubes, how far off the bottom of the tank should the intakes be placed?

I assume they can be cut to the desired length and the filter/screened intakes replaced on the tubes.

Too long and they'll pick up debris or water in the bottom of the tank, too high, and they'll waste fuel capacity by not picking up as much fuel as practically possible.

As a guess, I'd say 1 to 1 1/2', but I wonder what the directions (if any) on the pick up tube box says?

Joe.

[Almas Only]

For those who are going to be removing or working on fuel tanks, or changing out fittings, here's a suggestion: be VERY careful.

The fuel/air mixture inside gas tanks can be explosive, which is why spark arrestors are required. Although the tank is plastic, not metal, it's still capable of providing everything but the spark needed for an explosion. I would be particularly concerned about purging the tanks with air (which can introduce a static discharge to an accidentally grounded fitting), or sucking them out with a shop vac (which can introduce a spark in the vac, and a flame which would travel back to the tank).

I don't know if there is an accepted procedure for making a plastic tank safe to work on, but if you have any reason to believe that the vapors in the tank could possibly be ignited, you might consider filling the tank to overflow with water, and then removing only enough water to allow you to do the work. Once the work is completed, remove the rest of the water. The reason for not removing all the water at once is that plastic absorbs and is itself a source of vapors, and that sometimes you think you’ve purged all the gas out, but have managed to miss a little pocket. If you decide to drain all the water at once, you're still going to be way safer than had you not put the water in the tank to begin with. Draining the water onto an absorbant pad will catch any fuel or "gunk" that the water removes from the tank. If any water remains in the tank afterwards, it can be removed by letting the tank sit in the sun, or via the fuel/water separator.

I once did work for the wife of a poor fellow who managed to ignite what he thought had been purged from a tank. He hasn’t been doing boating, or much of anything, ever since.

[dogon dory]

Sorry, Folks - Post Deleted By Author

[Holoholo]

Thanks for the saftey check...it's better to be safe than sorry.

Vern