Running out of gas

I have a 1984 35hp Mercury and it has been running great. The last two trips out after trolling for a couple hours the engine would just run the gas out of the fuel line. I repeated pumping gas in the line several times and it just would run it out and die. I then pumped gas in and ran it at full throtle and it ran normal then slowed down to trolling speed and it ran fine again. Just before the first time this happened, I ran the boat in shore and there was a lot of brush and moss and I am starting to think that some of the moss may have gotten into the engine through the rear intake. Not sure if thats the case. Does anyone know what needs to be adjusted? I am going to check the lower unit but I know something else has to be adjusted just not sure what.

Re: Running out of gas

You need to rebuild the fuel pump and replace the fuel filter

Re: Running out of gas

Is the vent on fuel tank open and clear?

Re: Running out of gas

Yes the vent is open. I will have to check out the fuel filter, does anyone know where it is, I have a Seloc manual? Also is there a post that explains rebuilding the fuel pump? I try to do everything I can because of the rates at the boat shops. Thanks for the info.

Re: Running out of gas

Locate the fuel filter by following the fuel line where it enters the engine to the carb. The filter is somewhere in between.

Re: Running out of gas

Ok I just took a look at the fuel pump and it looked ok I took it off but couldn't get into it, didn't notice anything wrong. Then I took off the prop and noticed that there was a piece of debris that looked like coal stuck in one of the holes, not sure what it was, but it could have been wood from when I docked on shore.
Should there be a lot of lower engine gear oil, in the prop hole? Is the fuel filter thin and leathery? I think I took it off and cleaned it. It didn't have any tears so I don't think I need a new one. I put everything back together and it started up just like it was new, but I have to take it out and see how it runs. Thanks for the help.

Re: Running out of gas

Can anyone answer any of questions in my last post? Thanks

Re: Running out of gas

I think you disassembled and reassembled the fuel pump.

The prop hub will be oily. It's unburned 2 cycle oil because the exhaust goes through there. You should change the lower unit gear lube at least once a year, preferably before you put it to bed for the winter. If it's milky, or has water in it, the lower unit needs seal service. There should not be any lower unit lube on the prop at any time.

2 cycle oil and gear lube have very distinctly different smells. You should be able to sort it out with your nose.

If the hose goes dry, you either have a plugged pickup, or an air leak somewhere in the pickup or gas line to the engine. Often the pickup tube in the tank will come loose at the top and cause just that kind of trouble. When the tank is full, it seems to work fine, but when the fuel in the tank is low, the pickup sucks air and the engine starves. If you put a short piece of clear vinyl hose (temporarily) between the primer bulb and the engine, you'll see bubbles in the gas if it's sucking air.

hope it helps
John

Re: Running out of gas

After looking at the manual I have I did take the fuel pump off. Is that the fuel filter inside or is it just called a diaphagm? That makes sense because when I was haveing trouble the fuel was low, I still haven't tried it out yet so not sure if there is another problem. Should the prob hub be cleaned out or does it matter? Thanks for the information.

Re: Running out of gas

HTG said:

After looking at the manual I have I did take the fuel pump off. Is that the fuel filter inside or is it just called a diaphagm? That makes sense because when I was haveing trouble the fuel was low, I still haven't tried it out yet so not sure if there is another problem. Should the prob hub be cleaned out or does it matter? Thanks for the information.

Click to expand...

That's the diaphragm. It should be replaced if you disassemble the fuel pump, as it is a critical part.

The filter is usually a thumb sized in line thing beteen the fuel pump and the carbs. It might not have one.

I think the fiel pickup tube is sucking air. Go check it out.

Hub is always oily, unless the only 2 speeds you know are off and WOT. Then it's still dirty.

Hope it helps
John

Re: Running out of gas

Went out today and its purring like a kitten again. The low fuel caused the surging. I will have to buy another diaphragm and fuel filter while I'm at it. Is anyone cheaper than Mercury Express? Thanks again thats a great help.