Can't find replacement fuel pump for '07 25hp

Hi boaters,

Pretty frustrating as I've called a few places only to find out they don't carry a replacement fuel pump for my 2007, yamaha 25 HP 2 stroke (model MSH). Am I missing something here? I checked my manual, there is no replacement part listed for the fuel pump.

Just some background. My motor coughs/backfires at low rpms, does not do this at higher RPM's. Motor starts fine, gas was recently replaced. I opened up my cowling for a visual inspection the other day to find a tiny bit of fuel/oil underneath my fuel pump. I wonder if my motor symptoms could be from a faulty fuel pump?

The motor is also idling at high RPM's (like 1.5 RPM), but I think this is a separate issue that may have to do with idle/mix screw.

Any advice would be greatly appreciated. I could take the skiff out now, but it's a pain to dock due to coughing/high rpm at idle. I can call a guy, but both seem like a simple fix that maybe I could do myself. Thanks everyone and really look forward to hearing some responses!

-Brad

Do you have a model # by chance ?----2 stroke or 4 stroke motor ?----Have you looked on -------boats.net-----Some parts are listed there.

racerone said:

Do you have a model # by chance ?----2 stroke or 4 stroke motor ?----Have you looked on -------boats.net-----Some parts are listed there.

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Yes, sorry.

It's a 2 stroke (model MSH).

I checked a few websites, still nada. Maybe I'm not looking in the right spots? I even checked the existing fuel pump itself, no part # there either.

The fuel pump is right where the Yamaha parts catalog says that it is.

From what I am reading, the fuel pump is not the problem.

boscoe said:

The fuel pump is right where the Yamaha parts catalog says that it is.

From what I am reading, the fuel pump is not the problem.

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Thank you for the diagram boscoe, but were you able to find a part # for the fuel pump? Could you elaborate a little more on why you don't feel it's the fuel pump causing the issues? I appreciate any thoughts on the matter really.

There is a small drip of fuel coming from underneath the fuel pump itself, but that could also maybe be the fuel line. I just wonder what is making the motor cough at low RPM's and how I can lower the RPM's at neutral.

As I see it the pump does not come as a separate and complete assembly. Maybe that is what you are looking for. It is integral to the fuel bowl which is available for purchase. Item 3 in the illustration above. However, all of the piece parts that comprise the fuel pump can be purchased. Why buy a bunch of stuff you don't need if for instance just a diaphragm has gone bad.

Coughing and back firing is indicative of a lean air/fuel mixture. The fact that the motor runs well when at high power tells me the fuel pump is doing the job that it needs to do.

Running at high idle RPM could also be related to the air/fuel mix and/or just a simple idle RPM adjustment.

Now if there is a fuel leak then get that fixed. It could be related to the problem you are having. Fuel leaks are not normal and can be problematic at the least and dangerous at the worst.

Are you the original owner? Has anyone ever messed with the idle air jet and/or the idle RPM adjustment screw? Is the choke adjusted properly?

boscoe said:

As I see it the pump does not come as a separate and complete assembly. Maybe that is what you are looking for. It is integral to the fuel bowl which is available for purchase. Item 3 in the illustration above. However, all of the piece parts that comprise the fuel pump can be purchased. Why buy a bunch of stuff you don't need if for instance just a diaphragm has gone bad.

Coughing and back firing is indicative of a lean air/fuel mixture. The fact that the motor runs well when at high power tells me the fuel pump is doing the job that it needs to do.

Running at high idle RPM could also be related to the air/fuel mix and/or just a simple idle RPM adjustment.

Now if there is a fuel leak then get that fixed. It could be related to the problem you are having. Fuel leaks are not normal and can be problematic at the least and dangerous at the worst.

Are you the original owner? Has anyone ever messed with the idle air jet and/or the idle RPM adjustment screw? Is the choke adjusted properly?

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Thanks for the response and your time once again, Roscoe.

I am actually not the original owner and I do know the previous owner mentioned he has messed with the idle adjustment screw before. I'm thinking this is part of the problem, at least with the high RPM's at idle. The choke seems fine. Do you think the coughing at low RPM (<2 RPM) also has something to do with the idle adjustment? I hope so because it sounds like a simple fix. As for the leak, it's not very much at all, just very little oil that I found on the bottom of the fuel pump.

I'm thinking of turning idle adjustment screw once the motor is warmed up tomorrow and turning it counter clockwise until the RPM's begin to lower at idle. Would you agree that this is the best approach? If the manual says the idle adjustment should be at 3 1/4 turns for example, does that start from turning the screw counterclockwise all the way to the beginning to where it is loose and then counting 3 1/4 turns? Also, does the engine have to be warmed up before adjusting the screw or can I do it before starting it up? It's a lot easier when motor is off and not shaking to adjust, but whatever is best.

Sorry for all the questions, basic ones at that. I'm great at fixing things in the house, not so much with boats. Thanks Roscoe!

Just an update for anyone who may need this help down the road searching the internet like I did...Never did hear from Roscoe again or anyone else for that matter and that's a shame because a lot of people need help out there with their boats.

I ended up fixing the problem as it was the RPM idle adjustment (do this while running and watch the RPM gauge until you get the right idle speed a little < 1 rpm for me). I also added some seafoam and now I don't get any misfires and idles beautifully. Just remember when doing your idle adjustment that a little turning does a lot and counterclockwise reduces the idle speed and clockwise increases it. If anyone needs help down the road with this, just pm me, but it was fairly simple overall once you locate the right screw under to cowling.

Seafoam is a great thing. I will caution you and all with 2 stroke outboards... With the introduction of ethanol in our fuel, you can get major gumming issues in all outboards. When it comes to 2-stroke outboards, it can be especially deadly. Be sure to use the green marine Stabil ALL THE TIME. When it comes to winter storage, if you don't fog it and let it run itself out of gas, at least pull the fuel line and let it run until it runs itself out of gas and squirt some oil in the cylinders and then dry crank for 2 seconds. I fried a cylinder in a 75HP 2-stroke because I had a little gum built up in one of the brass fuel jets on one of the three carbs. It idled fine and it ran well but at high RPM it came up short on the top end. I didn't think too much of it but that one cylinder out of the three was receiving maybe 40% less fuel than it should have. That means it was getting less lubrication than it should have. Rings fried, cylinder walls scored, costly mistake. For craps and giggles, take those brass fuel jets out of the carbs each spring and make sure the orifices are perfectly clear and clean. Blast them with carb cleaner and run a thin copper wire through them to clear any really tough gum out (copper is softer than brass so it shouldn't scratch them and provide a place for gum to build up quickly). As they say, 2-strokes can last forever so long as they are run on a regular basis. Let them sit with this ethanol fuel in them and that will be the kiss of death.