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Here is the deal:

About 3 weeks ago I bought a 16' Mitchell to use as my donor boat for the 15' Whaler. It has a 2005 Yamaha F60 which the previous owner bought new. When I ran the boat at the guys house it ran great, idled fine etc. I brought the boat home, cleaned it up and took it out for the first time. It ran great for the first 15 minutes, jumped up on a plane and was pretty fast. Then it slowly had less and less power until we couldnt get it up on a plane and had to idle back to the boat ramp. The whole time it still idled fine and never quit, it was just low on power. Yesterday I replaced the water/fuel seperator, fuel lines and primer bulb. I also noticed a crack on one of the fuel tank fittings so I just dropped the fuel line into the tank for testing purposed. I took the boat out again and it ran great for the first 45 minutes. It was fast, planed will and I thought the problem was solved. Then it started to get a little slower until it quit. After that the motor would start right up, idle for 5-10 seconds and then quit. If we revved it up or gave it some gas we could sometimes get it on a plane and cruise until it quit after 30-45 seconds. We limped/got towed back to the ramp the rest of the way home. Could this still be a fuel issue or what do you think? If I disconnect the fuel line from the motor and pump the priming bulb there is still plenty of fuel making it through the filter and to the engine. What do you think?

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It reads like a fuel quality or delivery problem.

Is the existing tank a portable or in deck?

I would run it on a seperate portable tank with fresh fuel and a connected hose/primer.

Report back.

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I just went through a very similar set of circumstances on my 15' with a 70 Yamaha 2-stroke. After replacing the entire external fuel system (it needed it anyways, fiberglass tank and E-10 don't mix, I also had a fuel quick disconenct leaking) I was still having the same problem.

A local mechanic suggested I replace the on-engine fuel pump. I did that and have put about 45 miles on it (almost all going fast) without any problems.

I took the old fuel pump apart and everything looked intact... But no problems and it starts better now... 23 year old engine, once its primed, it starts with a quick touch of the key...

The fuel pump was easy to replace...disconenct the fuel lines to/from it and take out two bolts....

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How much was a new pump?

Update:

Ran the boat again yesterday after replacing the fuel with brand new 87, replacing fuel lines, checked inline filter, replaced primer bulb, replaced fuel line fittings and replacing the fuel/water seperator. Same thing happened as before. It started right up, revved fine, and moved at idles speed for 10 minutes with no issues. Then I gave it 3/4 throttle and it popped right up on a plane for about 2 minutes when it slowly lost power and got back to a plane. I tried to get it going again with no luck and it would only idle. Any ideas?

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Did you replace your fuel pump?? Does the motor come back to life after squeezing the fuel ball a few time??

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Buy the OEM service manual.

Follow the fuel line and find the 2nd fuel filter. It should be after the lift pump and inline. This filter should be replaced too.

Check your vapor separator tank (VST). Drain the contents and clean. The fuel pump is inside this part.

If the engine is bogging (runs fine then changes sound when more throttle is applied with no increase in speed) I would suspect clogged injectors due to debris.

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Where can I get the OEM manual? I was going to pick up a SELOC manual after work one of these days, will that work too? When you say 2nd fuel filter, do you mean the 2nd one after the fuel/water seperator I have mounted on the transom? Or is there 2 underneath the cowling. Can the injectors be cleaned if they are clogged or do they need to be replaced?Where can I find the VST?

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Do not get an aftermarket manual. You want the factory service manual - available many places but I recommend SIM Yamaha: http://www.simyamaha.com/category_s/1...s/1729.htm. The manuals are not cheap, but are well worth it.

Tim

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SIM is a great source. Look under fuel system for the diagrams.

Thee is a cartridge style fuel filter under the cover (follow the fuel line) before the fuel pump (aka lift pump). This gets fuel to the motor.

Here is the online parts diagram. You can select from a list in the upper left to see other areas.
http://www.yamaha-motor.com/partviewe...LR_-_2012)
If you follow the fuel line you may see a small cylinder in the fuel line. That is the second filter. There is a chance the F60 does not have one like my F115.

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Thanks, I have already checked/emptied that filter prior to the last outing. The local shop didn't have one in stock but I will be sure to buy one when I order the manual. Previous owner said Yamaha just did the 200 hour maintenance on it but what would you guys recommend for some preventative maintenance? Might as well order some parts while I am getting the manual.

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Ask Andy at SIMyamaha - explain the situation to him and I'll be he can work you through it.

Tim

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I don't think you have a fuel line problem. I think it's on the ignition side. Check the sparks from the power packs as well as the stator. When they get hot the faults appear - expand the material causing the gap to widen, for example.

When the engine dies after twenty mins or so what was the charge on the battery? If the battery is being charged between trips it will last for twenty minutes without a charge being applied and then die.... So also check the bridge rectifier charging circuit.

One last thing:

When you next run the boat and it starts to die manually prime the fuel line as fast as you can to see if it makes a difference.

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Remember, we are talking about a F60 4 stroke.

I would have the fuel injectors cleaned professionally.

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I had a yamaha 115 2-stroke that had similar problems. After spending a lot of time on things described here, I realized that the motor has overheat sensors on the block. There were two of them and the are inserted into small indentations in the block. Two wires [pink and yellow I think] are connected to them. The sensor is a round "button" like a camera battery used to be and simply pushes into the indented hole. I disconnected them and the motor ran fine. The motor was not overheating but the sensor was telling it that it was. I then bought new sensors. The labor involved was easier than screwing in a light bulb. Worth a try anyway.
With all the e-10 issues around it is easy to figure it is fuel; which is what I did for weeks also.
Good luck.

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Thanks. I purchased the Yamaha manual but there are so many yamaha specific tools I am kind of thinking this better be left to the pros.

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Keven -

My low hour 2003 F115 suffered from bogging (idled fine, got on a plane but no more speed) in 2007.

The Yamaha mechanic removed the 4 injectors and sent them to Flagship Marine (200 East Ann, Punta Gorda FL) for cleaning. He also cleaned the VST and replaced the filters.

Injector cleaning runs ~ $50 per and includes shipping and dealer markup. Think the entire bill was $500.