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Old 31-01-2014, 16:03   #1
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HELP: Yamaha 4hp outboard engine

Help!
My outboard (yamaha 4hp 4 stroke) is still not starting.
The carburetor has just been cleaned by a yamaha workshop and the spark plug is new. When I check the fuel flow into carburetor (take hose off from the carburetor and pull the starter rope) fuel spills out of the hose (looks nice). Even the spark plug makes nice sparks. Still the engine does not start at all. (in both choke positions).
I have opened the little drain screw on the carburetor and some fuel came out, not so much.
In the recent days I had repeatedly the problem that the engine suddenly stopped working which is why I have asked the workshop to clean the carburetor. (At that point I could not start it again)
I think they have done this job well!
After this service the engine worked fine for one day now but suddenly stopped again. Now I can't start it anymore.

We desperately need our dinghy with the outboard. We have two little kids on board and the coming 4 days the workshop is closed....

So what can I check next to find the problem?

Thanks in advance for all hints!
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Old 31-01-2014, 16:15   #2
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Re: HELP: Yamaha 4hp outboard engine

How good is the gas? Is it that ethanol crap that's been sitting in the tank for over a month?
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Old 31-01-2014, 16:40   #3
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Re: HELP: Yamaha 4hp outboard engine

Do you still have bad gas?

Here is a youtube on how to clean the carb yourself. It is easy
Make sure that you clean the filter and have new gas.

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Old 31-01-2014, 17:07   #4
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Re: HELP: Yamaha 4hp outboard engine

is it a two stroke or a four stroke? if a two stroke, i have a yamaha 3 which is the same engine. i also had problems where the engine would run and then not run, start and then not start.

you say you are getting fuel in to the carb, so the problem may be what the carb is doing with the fuel. if the engine smells of gas after a few pulls of the starter it is most likely the float in the fuel bowl stuck in the down position, allowing too much fuel into the carb. take out the bowl drain screw and lightly stick a paper clip up through the hole to exercise the float.

if you don't smell gas after a number of pulls, no fuel - or not enough fuel - is getting out of the bowl. check and clean your jets and any other passages in the carb. as a last resort check the reed valve to make sure it's free, although that is rarely the problem.

and like vasco says, most of the problems we have with fuel today is due to the inclusion of ethanol, which does not store well. try to keep stored fuel to a minimum whenever you can, always buying fresh. there are also some additives you can put in fuel storage cans that are supposed to help the situation. if you're not in the USA then you probably don't have this problem.

still, i think your first step should be to get a gallon of fresh gas from the local station, run it through a filter on the way into your tank, and drain any old gas from the engine before trying again. last time i had trouble with my yamaha 3 it was dirty gas; now i personally filter all gas before it goes in to the tank.

and don't be so sure that the 'workshop' did a good job of cleaning your carb. i gave my troublesome yamaha to the same 'workshop' three times and it continued to have intermitent problems. i finally decided it was not the carb, but the fuel pump that is intergral to the carb body. i rebuilt the fuel pump and end of problem....
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Old 31-01-2014, 17:43   #5
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Re: HELP: Yamaha 4hp outboard engine

I had similar problems with a 4 Hp, 4 stroke Tohatsu. I would get the carb cleaned, it would run for a day and then it wouldn't start again. Eventually I came to the conclusion that my portable fuel tank was contaminated. As long as I don't use it, it runs great. Now my problem is, what do I do with a half full portable tank of gas that is contaminated?
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Old 31-01-2014, 18:05   #6
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Re: HELP: Yamaha 4hp outboard engine

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Now my problem is, what do I do with a half full portable tank of gas that is contaminated?
I had five gallons of crappy ethanol gas. I took it to the beach, dug a little pit and poured it in. I then lit it (wasn't easy it was so crappy) and it burned off. The EPA or nsa (lower case so they don't pick this up) was not watching.
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Old 01-02-2014, 16:48   #7
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Re: HELP: Yamaha 4hp outboard engine

I have (had) the same engine. The carburetor has really small jets and chambers that you can't see. Takes ultrasonic cleaning to clean them out. I bought a 5hp Lehr propane to solve my problem.

I have spent $990 over the last 5 years cleaning carb, new tank, new hose, new fuel filter, etc. All 4 stroke under 15 hp have the same problem with this crap gas with ethanol. Great engine when it ran, just no good while cruising when it wouldn't run. If using an external tank make sure the hose is well attached on both ends. Last problem I had was bad hose connection at external tank in addition to all other problems - make sure it is solidly connected and not sucking air.
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Old 01-02-2014, 17:09   #8
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Re: HELP: Yamaha 4hp outboard engine

I researched one of these engines prior to deciding not to buy. They are reported to be one of the worst, most problematic engines yamaha eever made. I do not remember all the detaila why, but I would get rid of it. and get something else.
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Old 01-02-2014, 18:52   #9
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Re: HELP: Yamaha 4hp outboard engine

i'm beginning to feel thankful that i still have a two stroke engine. also good to know that you can buy new two stroke engines outside the USA, like in the bahamas.
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Old 02-02-2014, 05:53   #10
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Re: HELP: Yamaha 4hp outboard engine

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Originally Posted by onestepcsy37 View Post
i'm beginning to feel thankful that i still have a two stroke engine. also good to know that you can buy new two stroke engines outside the USA, like in the bahamas.
Doesn't help the OP but yes. Even though the fuel consumption is higher than a four stroke I bought a new 15hp two stroke to replace my old one. The old one had never been in the shop. Had to clean the carb every so often especially when my ethanol gas turned to piss. Change the plugs every season whether it needed it or not and changed the bottom end oil once in a while when I remembered.
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Old 02-02-2014, 06:17   #11
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Re: HELP: Yamaha 4hp outboard engine

I have the same 4hp engine one thing with these engines for some unknown reason is the float valve jams fully open indicating fuel bowel chamber is full i found by slightly moving the float pin over the one that the float swings on one way fixed the prob and the second prob it might be is the kill switch one way of testing this is to disconnect the white wire near spark plug and see if she starts
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Old 02-02-2014, 10:00   #12
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Re: HELP: Yamaha 4hp outboard engine

Quote:
Originally Posted by Vasco View Post
Doesn't help the OP but yes. Even though the fuel consumption is higher than a four stroke I bought a new 15hp two stroke to replace my old one. The old one had never been in the shop. Had to clean the carb every so often especially when my ethanol gas turned to piss. Change the plugs every season whether it needed it or not and changed the bottom end oil once in a while when I remembered.
i guess if i was cruising on a small boat with an auxiliary outboard i might choose a four stroke. then fuel consumption would become an important factor. but for just dinghying around i actually use oars on occasion...
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Old 02-02-2014, 11:20   #13
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Re: HELP: Yamaha 4hp outboard engine

Thanks for all your hints!!
Yes, it was very old fuel, but I don't think with Ethanol. Anyway I have replaced it by new fuel and the engine still won't run.
I found that the carbs 'cup' did not even get wet anymore.
I found a nice guy here in the bay, boatbuilder, who knows a lot about engines and he helped me to get this solved: The inlet valve into the card which gets actuated by the float was blocked by a little tiny black piece dirt. This must have ended up there after the reassembly of the engine in the service.
Now its all up and running again and - may be even more important - I will have no problems to solve such issues by my own in future because I have learned a lot!
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Old 02-02-2014, 12:37   #14
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Re: HELP: Yamaha 4hp outboard engine

yes, learn to clean the carb. probably 90% of outboard problems are carb/fuel related, now that cd ignition has replaced the old points/condensor system and mostly eliminated ignition problems. at the small horsepower level the carbs are fairly simple.....
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Old 02-02-2014, 13:25   #15
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Re: HELP: Yamaha 4hp outboard engine

Use Stabil fuel stabilizer. The green marine is better but red is OK. But always use the stabilizer even if you know your going to burn the fuel in a week and most of your problems will go away
Inline fuel filter wouldn't hurt too
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