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Yamaha outboard help


fishbum321

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I have a Yamaha F40 that fails after a few miles on hot afternoons.  it does not fail in the morning when it is cooler.  the engine goes from full power to zero power instantaneously and back to full power a few times and then will barely run at all.  It is in the shop and the say it has thrown no codes.  they have checked all the usual suspects to no avail.  they are looking to get help from Yamaha but have not had great success yet.  it has been in the shop only a few days.  this has rendered my HPX Micro inop and really want to get back on the water.   is there anyone out there that can help.

thanks

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34 minutes ago, Bamaskeet said:

I suggest you run the motor on a separate fuel tank to eliminate and fuel delivery issue.

X2, including hose, fittings, and bulb. Also, is bulb soft or hard when the events happen? Does it improve when pumped up? Sounds like a fuel problem, though. I’m not familiar with the smaller 4stroke frames, is it carborated or injected? Odd....no codes.

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entire fuel system reviewed.  shop has ruled boat out entirely.  bulb stays hard when it occur.  the loss of power is instantaneous.  not a fuel issue in my mind it does not fade away.  suddenly nothing like you hit something and then it comes back. just as quick until it wont come back.  it is injected it runs ok up to about 1000 rpm when it fails then stalls out.  I would think with 3 coils if one hiccups it would run rough not completely fail.  It is acting like there is a bad electrical joint somewhere that manifests when warmer.  all fuel filters etc replaced in June. 

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Fuel bulb did not help and replaced all filter annually.  Problem is limmited to hot afternoons.  I work with a ton of engineers all say eci after looking at schematic and knowing symptoms. No codes and changing failure modes and it progressively getting worse make me believe this as well. It is under warrenty so tech is following ser ice protocall i would have purchased the 600 dollar computer if not on warrenty. Will let you know where it goes. 

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I had the same issue with my Micro. If you have a 2012 you have an injected 40. Check the fuel cooler for obstructions like sand or dirt. It's super easy to get them clogged up. During long runs in hot weather we would get a vapor lock situation same at very low speeds like idle for long periods of time. Once everything cooled down all was fine. Wait 30 minutes and it will crank right up. I can't tell you how many times I got stuck up on a flat until I traded it in for a Honda. My dealer says there is a fix out for it. I also had a carbed 40 on my HPX 15 that was a piece of junk as well until I spent $2000 for a new gas tank and carb re-jeting.

good luck!

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I vote with Mulligan on th coil 

It may not be the coil  itself but it is something after the computer sends the signal to fire. The thing to understand about  fault codes is that the problem  needs to be  before or in the computer for it to know what is going on. Once it sends a  command it assumes it was done.

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This only made it as attachment last time so here goes.....

Yamaha F40 Fuel Issue

 

Thanks to all of the posters on this forum. Your advice has been very helpful to me in the past.  I’ve just completed a series of trouble-shooting procedures to try and isolate a problem I’ve been having with my 2009 Yamaha F40 and I’d like to pass along my experience:

After running the engine for a while at high power and then shutting it down, the engine would begin to stall/bog down the next time I tried to run it at speed. Also, while running at idle for about ten minutes, the engine would stall. In either case, pumping the primer bulb would bring the engine back to “normal” operation. Gradually this behavior began to worsen and occur more frequently so I took the boat to the local Yamaha dealer and had him check for any codes that the engine might have thrown. They said everything looked OK and said they would have to run it on the water in order to further diagnose the problem.  Since an on the water test here involves 3 hours of labor (at a minimum), I decided to try and figure out what was going on by myself.  I mistakenly believed that there was most likely some sort of air leak in the fuel system or perhaps a vapor lock. I replaced the fuel feed hose and it’s associated fittings from the Racor to the engine. While troubleshooting the problem further, I found that the engine mounted fuel filter housing was cracked allowing air to be drawn into the fuel system. The housing is not sold separately by Yamaha so I had to replace the entire assembly at a cost of nearly $200. Although this improved the performance of the engine, it did not solve the original problem, so I moved on to replacing the low pressure fuel pump which didn’t help either. From there, it was on to the fuel cooler. I found the water passages in the fuel cooler completely blocked with sediment so I cleaned them out and restored normal flow to the cooler. This did not improve the problem either. Finally, I checked the VST filter which I found to be discolored by a substance which had turned the filter black. Upon replacing the VST filter the engine ran normally. I assumed that the black substance blocking the VST filter had originated in the boat’s tank to engine fuel hose. Although I have only run Rec 90 fuel in this 14 year old boat, the previous owner most likely did not. As a precaution, I replaced the tank to engine fuel line. When I inspected the interior of the original fuel line, it appeared to be in decent shape with no cracking or delamination, but it did have a dull, somewhat weathered appearance which I attribute to some sort of erosion of the hose. I’ve put 105 hours on the engine since the VST filter replacement and it now seems to be running perfectly.

.

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I assume the answer after all that hard diagnosis was the VST issue.  This seems to be one of the main areas of Yamahas problems.  It should be the first thing to check out I guess.  I have a 40hp carbed which has been great after I  stopped using  E-10 and had the carbs rebuilt. 

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24 minutes ago, polliwog said:

VST issue.  This seems to be one of the main areas of Yamahas problems

It does seem to be an issue that always comes up.I have not read all the maintenance schedules for all Yamaha motors but for my motor the VST is part of the regular maintenance.  I am not sure why but there are a lot of people that overlook that little filter when it comes time to do their regular maintenance.

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