Yamaha 2.5 4 stroke issues - SailNet Community
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post #1 of 32 Old 06-26-2008 Thread Starter
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Yamaha 2.5 4 stroke issues

My 2004 Yamaha 2.5 4 stroke is having what I think are carb issues
(lo carb diet?)

After doing spring commisioning and testing last spring I loaned it to a friend last year as a kicker for his small sail boat and ultimately it got laid up without being used (read gas left in tank and carb for a year while laying in his basement).
I've drained the tank of the gummy gas, rinsed it with clean and refilled the tank. Drained all lines, drained the 'bowl' (really a tube) and cleaned it all out with carb cleaner and reinstalled the carb (and gasket).
The motor will start and run with starter fluid sprayed into the air intake, and will occasionally pop with no starter fluid - but will not continue running once you stop spraying starter fluid. I've worn deep blisters on the index fingers of both hands pulling the starter and beginning to give up.

It seems like it's a fuel flow problem. Yes the fuel shut off was open (and turned to closed as well just to make sure I did not reinstall it back wards).
I also tried to start it with the vent to the tank both closed, and open (normal).

I took it back apart and blew into the fuel intake housing (where the gas tube goes into the throttle body) and no air flow was apparent, but I'm not sure if that is a good measurement. In either case the results were the same.

Right now the entire carb is sitting in a can of gum-out soaking. I really don't want to have to dissemble the entire carb as I don't have a rebuild kit and don't know the adjustments etc.. I'd have to make.

Anyone got any tips, hints, tricks or tales?
(besides not loaning equipment to friends
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post #2 of 32 Old 06-26-2008
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Take it to a repair shop, send your friend the bill. I have been there and you pull so many times that you end up crawling away rather then walking. Let go the stress, take it to be repaired.

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post #3 of 32 Old 06-26-2008
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I have the same engine and went throught the same situation to find the vent in the fuel tank plugged, found this by providing a separate fuel source.

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post #4 of 32 Old 06-26-2008 Thread Starter
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Free, motor's worth 500, the shop costs 95 a hour, 3 hour minimum and as I said it's a friend - and he's standing right next to me as I work on it (it's sitting on a rack at his house now). Repair shop is not a option.

Art, I took the top off the tank just to check that, didn't help.
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post #5 of 32 Old 06-26-2008
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A couple of dollars spent on fuel lines (you didn't mention whether or not you replace them) would be a good idea. Before you cut and install the new fuel line, attach it to the carb still too long and filled with gas (be creative but careful) with the open end held up high. See if it will crank and run the gas out of the line. If it will, then the carb is ok.

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post #6 of 32 Old 06-26-2008 Thread Starter
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I did not replace the fuel lines because when I detached them from the carb the fuel ran just fine all over my index fingers newly blistered and open sores. Fuel appears to run just f%&ing fine up to the brass tube that goes into the throttle body.
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post #7 of 32 Old 06-26-2008
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Ahhh... welcome to the wonderful world of 4 strokes. I had two strokes for a long time and hardly ever had issues. Is it just me, Chuckles, or do you feel like they suddenly decided one day to switch over to 4 strokes (and take away the 2's) without actually trying to start one at the factory?????

I have a Merc 6 that runs really well after every $300 tune up bill, until the 90 warranty is off and it is right back to CHug... spit... chug... die unless you have 1000 rpms on it.

Is your engine made by Tihatsu? I think it is.

At any rate, this will not help your current woes, but I have found the ONLY way to prolong (key word P-R-O-L-O-N-G) the time between shop visits is to run it dry everytime you go to put her up. Pull the fuel line and just let her go until she is dead (and I mean that in every possible sense). I also run a fuel cleaner in her. THis has helped considerably. If you do not run her dry each time, you will be faced with the same problem (exception is when you run her everyday. When we were Liveaboards, this was never a problem. Go figure??).

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post #8 of 32 Old 06-26-2008
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Chuckles....

More bad news I'm afraid.......

I have a 2005 Yamaha 4hp 4 Stroke.... guy owed me money... Anyway mine sat for a year w/gas and it got so gummed up even though I took the carb off and cleaned it in the whoptie sonic aircraft parts cleaner at work....

I still had to rebuild it...it was just too gummed up even for the nuclear cleaner's I used on it.


Also sitting killed my fuel pump too...

Best of luck,

Tim

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no name yet (it's in pieces!)
Coconut Grove, Florida
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post #9 of 32 Old 06-26-2008
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I had the same problem w my 3.5 Tuhatsu. Thought I'd cleaned it out and it ran rough and only w the choke on. A friend suggested the needle valve was clogged so I added some carb cleaner to the gas. I put it in a barrel and got it running like a kitten in about 10 minutes.

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post #10 of 32 Old 06-26-2008
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Quote:
A friend suggested the needle valve was clogged so I added some carb cleaner to the gas. I put it in a barrel and got it running like a kitten in about 10 minutes.
I use to use carb clearner so much, a friend of mine, called it tune up in a can.

S/V Scheherazade
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I had a dream, I was sailing, I was happy, I was even smiling. Then I looked down and saw that I was on a multi-hull and woke up suddenly in a cold sweat.
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