97 25hp 2 stroke fuel issue

Jamesaelliott

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I’m sure somewhere around here is. Always been a DIYer. I’m always scared of them labor costs. But I may just have to bite the bullet on this one and find a mechanic.
 

racerone

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Some simple testing will find the issue.-----But I know from many threads here that folks want to hear about an instant fix.----Reluctant to do the testing.
 

Jamesaelliott

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Well, if you read my original thread, I’ve done the testing, and replaced every inch of fuel related part. That is why I’m here. Hoping that someone would have a similar resolved issue. I mean, at the end of the day, that’s why these forums are here, right? To find help, suggestions or opinions? So, yes people come here to find answers.
 

racerone

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See post #18 ?-----Your answer is ?----I have a 25 Yamaha that I got for a favor for a dealer.----Good looking motor with lower unit missing.----Have not done any work to it yet.
 
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Jamesaelliott

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See post #18 ?-----Your answer is ?----I have a 25 Yamaha that I got for a favor for a dealer.----Good looking motor with lower unit missing.----Have not done any work to it yet.
I replied back to you on post 19. If the flywheel key was broke or sheared, my time marks wouldn’t line up when pistons are top dead center.
 

Jamesaelliott

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After speaking to a guy on a Facebook group, I believe I am getting too much fuel at higher throttle. Little to no fuel is shooting out of the main jet into the carburetor at idle to almost the point of it bogging down. Once it reaches bog point fuel is almost pouring out. Not sure if it’s normal or not. I did try adjusting fuel/air screw, for more air less gas. But it idled worse and died.
 

99yam40

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No fuel should be flowing thru the main jet into the motor during idle.
as I said check to make sure the timing is advanceing as the extra fuel starts hitting the motor.

or just tak it into a shop to let them fix it
 

Jamesaelliott

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No fuel should be flowing thru the main jet into the motor during idle.
as I said check to make sure the timing is advanceing as the extra fuel starts hitting the motor
Everything on top end is moving like it should as far as I can see. Timing advances a litttle bit while In neutral, once shifted into gear obviously it has a much broader advancement and it stops maybe an 1/8th of inch before the stopper peg, “what ever it’s called”
 

99yam40

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Everything on top end is moving like it should as far as I can see. Timing advances a litttle bit while In neutral, once shifted into gear obviously it has a much broader advancement and it stops maybe an 1/8th of inch before the stopper peg, “what ever it’s called”
is the idle timing in spec and does it show as it advances when throttled up.
guessing does not help.
check with a timing light
 

Jamesaelliott

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is the idle timing in spec and does it show as it advances when throttled up.
guessing does not help.
check with a timing light
Just out of curiosity,, I’ve never messed with a timing light before so this may be an invalid question. Beings there’s timing marks on the the flywheel for “I think” 10, 20, and TDC probably wrong on the degrees without looking at it. Then the timing mark on motor. To my knowledge everything is in time by those marks and seen plain as day. If those marks were revelent to OEM specs, and seem to be visually correct, what would a timing light do? Where would you point a timing light? I’m dying to get back on the water to fish, not to mention duck season is 30 days away. That’s why ive dumped so much money in fuel related parts and carb cleaner. You would think from one great running tripS to a not running trip would be a clear sign of fuel relation. I can pull a motor apart all the way down to its core and put back to together, done it several times in my life. However timing, never bothered with it other than OEM time marks. You tell me to use a timing light and I’m lost, Genuinely asking.
 

Jamesaelliott

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is the idle timing in spec and does it show as it advances when throttled up.
guessing does not help.
check with a timing light
I can do pretty much anything myself, if I don’t know from experience a simple google search is my friend. Finding nothing on this specific model Yamaha is now a concerning factor. Parts, specifically the carburetor, is apparently discontinued as well as rebuild kits. Haven’t done much research on it but as far as I’m concerned Yamaha dropped the ball on this model outboard. Sucks I ended up with it and will probably have hell getting rid of it, but it will for sure be in the works
 

99yam40

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Just out of curiosity,, I’ve never messed with a timing light before so this may be an invalid question. Beings there’s timing marks on the the flywheel for “I think” 10, 20, and TDC probably wrong on the degrees without looking at it. Then the timing mark on motor. To my knowledge everything is in time by those marks and seen plain as day. If those marks were revelent to OEM specs, and seem to be visually correct, what would a timing light do? Where would you point a timing light? I’m dying to get back on the water to fish, not to mention duck season is 30 days away. That’s why ive dumped so much money in fuel related parts and carb cleaner. You would think from one great running tripS to a not running trip would be a clear sign of fuel relation. I can pull a motor apart all the way down to its core and put back to together, done it several times in my life. However timing, never bothered with it other than OEM time marks. You tell me to use a timing light and I’m lost, Genuinely asking.
the light tells you when the spark is happening.
idle timing is usually ATDC (after top dead center) it should advance to BTDC( before top dead center) to be able to burn the extra fuel at higher RPM

there is a reason they give you the specs in the service manual( so you can check it)
 

99yam40

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My 1999 C40 specs are 7 deg ATDC at idle and 25 deg BTDC at full advance.
I have no idea what the specs are for your 25
 
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