DF15 Losing Speed

[iliketurtles813]

This is my first post, but I was a long time lurker before joining.

Anyways, I noticed my 99 four stroke DF15 was losing a few mph off the top speed and had trouble cold starting. I was told by my mechanic to replace the fuel line, fuel filter, and put an inline filter in. There was some pitting in the lines and there was a considerable amount orange gunk in the filter. It fixed the the cold starting problem, but the boat just doesn't go as fast as it used to. I tried running some carburetor cleaner, but that didn't help.

I recall my mechanic saying to replace the carburetor diaphragm, but I'm not sure which part it is on the diagram.

My best guess is ref # 1
http://store.brownspoint.com/df15-02/fig011.asp

Any other suggestions to fix this problem?

 

[Handyman1]

Re: DF15 Losing Speed

Hi and welcome first you should check compression and the fuel pump if everything is ok then you have a dirty carb.

 

[NetDoc]

Re: DF15 Losing Speed

That carb does not have a diaphragm. Part #1 is the gasket between the intake and the carb.

 

[robert graham]

Re: DF15 Losing Speed

If you had "orange gunk" in the filter then it's probably in the carburetor, maybe disassemble and clean carb, or have it done by a Yamaha dealer. Start using Stabil in your fuel to help keep it fresh, especially if it sits in the tank for days and weeks between usage. The gas now with ethanol breaks down and deteriorates rapidly causing deposits and "orange gunk'...Good Luck!

 

[iliketurtles813]

Re: DF15 Losing Speed

Thanks for the input. I had a feeling I was going to have to take apart the carburetor. It was rebuild last year, because the boat was sitting for a while. I'm not about to pay someone a few hundred again to take apart the carb, so does anyone know a link to a guide, because I haven't found any that were a similar make to the DF15 ?

 

[NetDoc]

Re: DF15 Losing Speed

Looking at that diagram, its as simple as a lawn mower engine. Be sure to replace items 1, 14, 19 and 28. They probably come in a carb rebuild kit. Take your time and have fun with it. The specs on how to set the linkage and float level are probably in the kit. I would go at that with a can or two of carb cleaner if you didn't have a bucket of dip. Do the disassembly on a restaurant tray to help you control the parts. Have a camera on hand and takes lots of pictures for reference. You can't take too many pictures.

Restaurant Tray​

 

[iliketurtles813]

Re: DF15 Losing Speed

Looking at that diagram, its as simple as a lawn mower engine. Be sure to replace items 1, 14, 19 and 28. They probably come in a carb rebuild kit. Take your time and have fun with it. The specs on how to set the linkage and float level are probably in the kit. I would go at that with a can or two of carb cleaner if you didn't have a bucket of dip. Do the disassembly on a restaurant tray to help you control the parts. Have a camera on hand and takes lots of pictures for reference. You can't take too many pictures.

Restaurant Tray​

Thank you that's very helpful, but I'm not sure if it qualifies me to take apart the carburetor. Excuse my lack of knowledge, the most I've done to the engine is changing the impeller and oil. All of those tiny pieces in the carburetor scare me.