Yamaha 2 stroke fuel pump

tech_dog

tech_dog

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I broke a barb off one of my 95 Yamaha 175 2 stroke fuel pumps while changing out my hoses, a $50 mistake. It turns out the face plate is metal but the body is grey plastic and I should have been more gentle. It's an exceptionally easy job to remove and replace these.

What's got me baffled is that there's no apparent power being delivered to the pump, no electrical connections and no mechanical drive. Does anyone know how this works? I'm guessing there's some sort of magnetic interface, but that's just a desperate guess. Are these just magic?

T.
 
Take the old one apart and you'll find rubber diaphragms inside. Look on the side of the pump case that attaches to the engine - see the holes? As the pistons travel they create alternating suction/pressure which moves the diaphragm in/out and along with the check valves inside the pump it draws the gas.
 
If you have multiple low pressure pumps and they may be original ( there is a way to tell by lookin at the color of the diaphragm material ) you should replace all of the pumps.

I can't remember at this moment what the colors but look at a new pump and note the color of the diaphragm. It should have a tab sticking out a bit. I think newer pumps have black diaphragms but just compare the new to the old. If the old are a different color, they are older models)
 
DennisG01 said:
Take the old one apart and you'll find rubber diaphragms inside. Look on the side of the pump case that attaches to the engine - see the holes? As the pistons travel they create alternating suction/pressure which moves the diaphragm in/out and along with the check valves inside the pump it draws the gas.
Click to expand...
That appears to be it. The two holes on the side are for mounting, the one in the middle must be the port for the alternating pressure/suction.

This photo is the new one, and both old and new have the black tabs.


1705616459731.png

Thanks,

T.
 
seasick said:
If you have multiple low pressure pumps and they may be original ( there is a way to tell by lookin at the color of the diaphragm material ) you should replace all of the pumps.

I can't remember at this moment what the colors but look at a new pump and note the color of the diaphragm. It should have a tab sticking out a bit. I think newer pumps have black diaphragms but just compare the new to the old. If the old are a different color, they are older models)
Click to expand...
Good point. Even though old and new had black tabs, I just ordered a second so I could be sure both are new and matched.

T.
 
Side note... there's no way those are original or anywhere NEAR original! Give or take, figure replacing every 5 years. If you get a decent amount longer than that... consider it a bonus :)
 
DennisG01 said:
Side note... there's no way those are original or anywhere NEAR original! Give or take, figure replacing every 5 years. If you get a decent amount longer than that... consider it a bonus :)
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Dennis,
I didn't see any pics of the old pumps. How are you sure there is no way they are original? The fact that the tabs are black??
 
seasick said:
Dennis,
I didn't see any pics of the old pumps. How are you sure there is no way they are original? The fact that the tabs are black??
Click to expand...
No, it's been my personal experience (and have read WAY more about these pumps than I should!) that the diaphragms and seals just don't last all that long. They're basically considered a regular maintenance item. Rebuild kits are available - but they're not THAT much less than a brand new pump (fully assembled) ready to bolt on. In this case, his engine is nearly 3 decades old :)
 
seasick said:
Dennis,
I didn't see any pics of the old pumps. How are you sure there is no way they are original? The fact that the tabs are black??
Click to expand...
To the best of my knowledge, I was was replacing the original 30 year old fuel pumps. I've owned this boat since new, but used to have a co-owner that sometimes did work, most of it wrong and cosmetic. There's s a very slim chance he replaced them without charging me half, but it's unlikely.

I also read stories of fuel pumps leaking after a few years, and I think counterfeit parts may be the reason. I'm convinced that most of the sellers on Amazon are selling cheap fakes, and I only buy from dedicated marine retailers for that reason. Ever notice how cheap and available 316 hardware is on Amazon?

I just changed out all the 30 year old rubber and plastic from the fuel tank to the carbs, and to be honest it was all extremely clean and looked good as new. I'm sure it needed it, but none of it looked like it was on its last legs.
 
tech_dog said:
To the best of my knowledge, I was was replacing the original 30 year old fuel pumps. I've owned this boat since new, but used to have a co-owner that sometimes did work, most of it wrong and cosmetic. There's s a very slim chance he replaced them without charging me half, but it's unlikely.

I also read stories of fuel pumps leaking after a few years, and I think counterfeit parts may be the reason. I'm convinced that most of the sellers on Amazon are selling cheap fakes, and I only buy from dedicated marine retailers for that reason. Ever notice how cheap and available 316 hardware is on Amazon?

I just changed out all the 30 year old rubber and plastic from the fuel tank to the carbs, and to be honest it was all extremely clean and looked good as new. I'm sure it needed it, but none of it looked like it was on its last legs.
Click to expand...
I only use Yamaha stuff for things like this, as well. I'd be very surprised if it WAS original... but hey, it COULD be! :)
 
I think that Yamaha purchased on Amazon or Ebay isn't always Yamaha.
 
I don't keep a good repair log, but I do usually take photos, so that I know how to put it back together, and they are dated. On things like pumps, starters, filters, etc, I also write the date on it with a Sharpie.
 
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