How to check fuel pump

[Karla45]

I am wanting to check and see if diaphragm on my fuel pump needs to be replaced. What do I look for in order to know whether it is bad or good. Before I got my boat it had been sitting for 5 years. I have some issues of it dying when i slow down and also when i slow down to put into neutral. I was told to adjust idle screw first and then maybe carbs to fix this problem. I am wanting to check the fuel pump to avoid any future problems. Would rather be fishiing than getting stuck on the lake and dealing with motor problems

 

[Frank Acampora]

Re: How to check fuel pump

The fuel pump diaphragm is only about three dollars and the gasket is less. If you are worried, why bother checking it? Simply replace it! It probably needs replacing anyhow.

They do tend to get hard and wrinkled with age. Sometimes they tear or get pinholes in them, and they can start to shed rubber particles. These are what you look for.

The pump is not the cause of stalling when you slow down unless it is leaking fuel through the diaphragm, Low speed stalling can most commonly be due to fouled plugs and too low an idle speed. Correct these conditions first, but replace the diaphragm anyway as preventive maintenance.

 

[Karla45]

Re: How to check fuel pump

I had already been looking on sites for the part but my problem is that everytime i try this they want model number and other numbers so then i get confused on if i am ordering right part to fit my boat. I have 1989 85HP Us Marine. Where on the motor could i find these numbers if any.

 

[Frank Acampora]

Re: How to check fuel pump

Either go to any Mercury dealer and ask for a diaphragm from an 85 to 125 Force--they were all the same part until changed to the square mercury pump-- OR contact franzmarine@aol.com. Franz doesn't need part numbers. He has forgotten more than I'll ever know. OR---Buy the kit here at iboats for 15 bucks or so -- part 18-7806

 

[Karla45]

Re: How to check fuel pump

HOw can i tell if any of these are fouled?

 

[jerryjerry05]

Re: How to check fuel pump

Plugs look good.At any hardware store they sell wire brushes.Get the stainless steel one.Use it anytime you feel the urge to tinker.
These type plugs can last as long as you own the boat.
Get a compression tester and learn how to use it.That is one of the best tools an outboard owner can have.
Then inline spark testers.
Carry a spare set of plugs or the brush and a spare diaphram.One backfire can poke a hole in the diaphram.
Learn all you can about Ethanol.J

 

[Frank Acampora]

Re: How to check fuel pump

If those plugs have all been run the same amount of time and if you have not cleaned them, you need to check your carbs!

The plug on the right shows very little oil and carbon on the porcelain (Notice how it is almost pure white as opposed to the other two?) and very little accumulation on the steel shell, indicating it is possibly not getting as much fuel as the other two.

If that cylinder is indeed running leaner than the other two, there is a danger of detonation at full throttle.

First, search and read my post on synchronizing carbs and timing. Second, be certain that that carb is clean and set correctly.

 

[Karla45]

Re: How to check fuel pump

Fortunately, i have not run the boat at full throttle. I think that I rubbed that spark plug with finger to see what it was. I do not think that that is carbon on them it is silver from the plug, my camera may have made the silver look white. Is there supposed to be carbon on the plugs? I will check everything out like you said. I was trying to buy a manual online last night. I am wanting clymer but could only find ones for force/chrysler up to the year 1988 and mine is a 1989. I know there are ones that say force only that include my year and horsepower but not sure if this would be correct manual. Could someone help me out here? Motor is 989 85HP Us Marine/Force. Is U.S. Marine considered a chrysler? On the issue of inline spark tester that was recommended, is this to test the plug or to see if cylinders are firing?

 

[moparman]

Re: How to check fuel pump

Karla45, the spark tester is usually used to check the firing of the cylinders, just a side note,if you are going to write on the plugs with a marker of any kind either remove it before reinstalling it in the motor or write on the metal base as marking on the porcelain tends to promote spark flashover,as the spark is hunting the path of least resistance and the marker ink will allow it to jump to it instead of firing through the tip. The ribs on the porcelain are to keep flash over from happening but when it collects debris on it it will happen.just my two cents worth