1987 Mercriuser 3.0L Ran out of gas?

[UNSUREBOATGUY]

After a great day out on the water, our boat started to sputter a bit while pulling two tubes around the lake (big turns, lots of lean, etc.) like it was running out of gas. Leveled the boat out and it ran fine again. Parked for a bit, warned the folks we were out on the lake with that we might be running out of gas Started the boat back up and started the long trip back to the dock, and the boat was running great for a while, then sputtered out again until it died. (Seemed like it was totally out of gas.) Our friends towed us back to the dock, and I tried to start it once more because it would be a lot easier to dock under power, but it sputtered out and died right away. Everything to me says we simply ran out of gas.

Stopped by the gas station on the way home to see how much it would take to fill the tank to see if it was just a lack of fuel issue, or if it might be something else. Filled with close to 15 gallons, which is the most I have ever put in the tank by a couple of gallons (we've never run out of gas before ).

Here's why I ask the question-the tank is supposed to hold 19 gallons according to the old specs I found.

Is it possible I have 4 gallons of water or something in the bottom of the tank? Seems very unlikely to me as the boat has been running great for years. I did start using the regular 87 octane gas with 10% ethanol this summer where I had always used no-ethanol in the past because it seemed silly to spend the extra money if I didn't have to, and I didn't notice any difference in performance. That also seems an unlikely culprit, but I thought I'd mention it just in case.

Full disclosure-I have a water separating spin on fuel filter on the boat that I have not changed in years. I ordered a new one last night. I will check the contents of the old one when I pull it off the boat to put on the new one. Is it possible that the fuel filter just reached it's limit of junk?

By the way, the boat is always parked in the garage when not on the lake, so it stays nice and dry. (Except for the humidity of WI summer).

Thank you!

 

[alldodge]

Tank pickup tube is close to the bottom, so if there was water in the tank it would be sucked out first. The water would fill the canister filter next. If its running out of gas then the pickup tube may have broken or corroded off the end. If tube is now shorter then this would cause it to run out sooner.

Another thing which may cause the symptom of running out, would be if the fuel pump is getting weak and unable to pull fuel when the tank gets lower

See if you can remove the pickup tube and check fuel pressure

 

[UNSUREBOATGUY]

Thank you. I'll take apart the tank access as soon as I can and take a look. Might have to be this evening.

The fuel pump is mechanical on the block, and fairly new (hours wise anyway). Do the mechanical pumps get weak before they fail?

 

[UNSUREBOATGUY]

Hmmm....I took a quick look at the fuel pickup on the tank while on my way down to my shop, and I'm not sure if I would be able to get it out without cutting out a small piece of the floor Is it common for the pickup tube to go bad? The tank does say 19 gal capacity on the plate.

 

[alldodge]

Is it common for the pickup tube to go bad? The tank does say 19 gal capacity on the plate.

Normally no
Maybe try something like this; get the tank down low and remove the fuel sender. Use a outboard hand pump or other safe method to get the tank down to maybe having a gallon left.

Reinstall sender and then attach a outboard hand pump bulb on the autisiphon valve. See if you can suck any fuel out with primer bulb. If no, add 1 gallon to tank and try again. Repeat until you can get gas out.

 

[UNSUREBOATGUY]

Thank you very much. I'll see what I can do. If I can figure out a good way to pull the pickup tube, I'll try to measure to see if it goes to the bottom of the tank. If not, i'll try your idea to find out.

Forgive me if this is a dumb question, but are most pickup assemblies the same size (same fitting threads, etc.)? I haven't done a ton of research yet. I would like to have a new one on hand in case I mess up the old one removing it or find that it needs replacing. Also, can one adjust the length of the pickup tube by cutting it to length on the top end?

 

[alldodge]

Have not removed enough tubes to say they are the same, only all I have removed are 3/8

 

[UNSUREBOATGUY]

Well, I pulled the water separating fuel filter and emptied into a clear container. Nothing but clean nice gas as far as I could tell (I let it sit for a while to see if anything would separate out.) I made a small notch in the floor right above the fuel pickup tube (still covered by the engine cover when closed), and pulled the tube. It still looked to be in good condition. I measured and found it to be about 3/8" to 1/2" or so short of the bottom of the tank. I cut the new pickup tube so it would be just about to the bottom of the tank (with a good notch for the gas to get in of course ) and installed. I put everything back together and it ran perfect.

Is it possible that the 3/8" to 1/2" gap from the bottom of the tank was enough to leave 4 gallons in the tank? I suppose it's possible it didn't get totally full at the gas station, but it was flat and level on the trailer, and the pump stopped itself with the tiny bit of spill from the filler tube. The tank is a flat rectangle 6' deep by something like 24" x 30". I suppose the angle of the boat underway may have made a difference, but I thought we were pretty level. Next time (hopefully never) we seem to be running out of gas, I'll have everyone go the the back corner of the boat to get all the gas to the pickup tube

I'm happy it seems to have been nothing other than underestimating the amount of gas we were burning. It was a long day on the water with a long, fast (for our boat anyway-following friends with a 19' bowrunner with ac 5.7) run down the river and a bunch of tubing, skiing, etc., then a long run back. I'll have to be more careful next time, I guess. Thankfully we had good friends willing to tow us the rest of the way back.

Now to try to adjust the fuel sender when the tank is almost empty so it reads more accurately instead of reading empty at more than half a tank By the way, is that a symptom of the float being fuel logged, or probably just out of adjustment?

Thanks a bunch and happy boating.

 

[Searay205]

why wouldn't you just fill up and take back to water and try before disassembling the boat? if it only had 4 gallons left you ran out of gas. gas slouching around on lake pretty easy to see how it would move away from pick up tube. drill a hole in the bottom of your seperating fuel filter that is where the water would be.