40 HP Yamaha keeps clogging carbs

[40yamahammer]

I have a 40 HP yamaha that I aquired. It ran good for about 30 minutes then starting rough idel and skipping. I took it to the shop and they cleaned all 3 carbs and fuel filter. It ran fine again for about another 30 minutes and then it had no power at all. At full throttle it didnt have enough power to plane my jon boat out. I take it back to the shop and he says the No.2 carb is trashed up again and the fuel filter is filthy again. I am trying to figure out what could have caused so much trash in the fuel both times. The gas tank is brand new. I did have some tempo fuel line from tank to motor, which i have heard can break apart and cause this. Is this a likely cause, or could I have gotten a batch of bad gas that would cause this?? Any help would be appreciated.

[Bay Catt]

These problems you are haveing seem to be common place with us boaters since the ethonol gas came out. Try the simple things first to narrow your search down some. Empty the strainer,Blow it out with air and check the o-ring seal. Look at the upper part where the bowl connects for any dirt or perhaps a piece of an old o-ring. Drain the carb bowls by removeing the drain screws on each carb bowl and then reinstall them. Take a regular gas can with fresh gas in it. Drop the intake line before your primer bulk into the tank, prime the engine and then start it. Allow it to run for a good 15 minutes then start throtteling up and down with quick short blast. Repeat this over and over. What you will be doing is trying to push through any foriegn crap that may be in your carbs. This is done best if you manually move the throttle linkage. Wait to see if it made a difference. If problem is still there start checking some other things. If you question the fuel line from your tank go ahead and change it. Look at all the fuel lines and connections. Change the fitting on the primer line that connects to the motor.Cost about $4.00. There is an o-ring in there that may be bad causeing your engine to suck in air. check the main feed fuel lines from that point up to the carbs. Again if you question any of them they need to be replaced. check all the bolts and screws on the air intakes and the carbs to insure everything is seated properly. Do not over tighten anything, the engine houseing is made from cast aluminum and you can strip threads easily. Check to make sure the plugs are tight, or better yet change the plugs. Check all electrical connections including the ground, clean or replace anything needing attention. Check your battery for proper voltage and charging. Start it up again still useing the fresh gas. All of the things mentioned are relativly easy to do but it is time consuming. The parts are inexpensive, however use good quality and not any aftermarket parts. This may seem like a lot to do but it is a must to eliminate any small causes that can produce big problems. Any parts you may need can be bought on this web site and their shipping is fairly quick. You can also find a parts manual to ID all of your parts. Let me know how you make out.

[40yamahammer]

The fuel lines from thank to motor have been replaced. The carb has just been cleaned by the mechanic as well as the filter...So I think Im in order now...is there anything i can do to prevent this from happening again??

[Bay Catt]

perhaps a fine micron fuel/water seperator.

[40yamahammer]

I was thinking of getting a racon seperator. What size or model Racon would I need for the 40HP?

[Bay Catt]

Not sure what brand is Racon but it should not matter as long as the element is a 20 micron.

u need a 10 micron now with the new fuel evrybody will be getting in te next years

[Deepwatertroller]

I was going to put a single Sierra water seperator with 2 fuel line feeds going to filter and 2 going out for my main motor and kicker motor. Yamaha mechanic advised against it because it would place to much restriction. He said factor fuel/water seperators were adequate. I guess if you've had one on your boat for a while with no problem than I was misled. I'm leaning toward installing water seperator and seeing what happens. I haven't had a fuel/water problem yet but don't want to test my luck.