2007 25 hp Yamaha 4-Stroke Start Issues

[novascotia_zodiac]

A photo from January 2016 in Lobster Bay, Nova Scotia. August and September are the best months around here since there is little fog and it is still fairly warm.

[99yam40]

I am glad there are people that enjoy the snow,ice and cold, I do not.
it would be very crowded down here along the coast of the GOM if no one liked the cold

[boscoe99]

Lots of time left yet....all of Aug, Sept, and Oct!! You wont be out in October with your shorts on though...which is fine with me.

If it never went over 20C I would be fine with that, I don't like the heat.

If it never got below 20C I would be fine with that. I don't like the cold.

[novascotia_zodiac]

I'd rather just replace the prime start rather than try to measure the plunger length, and see if that helps, as long as it isn't too overpriced. There is a Yamaha dealership nearby that I can get it from.

Turns out the prime start is rather expensive at $200-300. Looks like I'll be trying to measure the plunger length first. I should be able to get the local Yamaha Dealer to do that.

[99yam40]

heck, you just pull it out and measur, and then put 12VDC on it and measure again to see if it moves.
it is not that hard to do

[novascotia_zodiac]

heck, you just pull it out and measur, and then put 12VDC on it and measure again to see if it moves.
it is not that hard to do

Sure, but I need to know what to compare the measurement to. Also, what about how quick it might go back to "cold" mode?

[TownsendsFJR1300]

Sure, but I need to know what to compare the measurement to. Also, what about how quick it might go back to "cold" mode?

About 13 minutes into the video:


https://www.youtube.com/watch?v=x35uqVMu2r0

[99yam40]

that video was not on a 4 stroke, and I do not know how far the F25 PS unit should extend, but my thoughts are as long as it extends it should be working..

time wise , how long does it take for you motor to warm up once started?
should be a few minutes, so that is how long to put 12V on it.

problem is if it does extend during the test, you still do not know if there is power getting to that unit while running unless you test that also,

does this motor have an emergency valve you can turn to get the motor started if things fail?
if so what position is that in right now.
hopefully it is in the normal/auto position.
not the on or off position

[panasonic]

Zodiac.

It appears that Yamaha made the F25A engine type with prefix 65W for approximately 10 years starting in 1998, with changes and improvement's along the way, but essentially the same engine.

As Yam said take out the prime start and test it yourself, it is only one screw and you don't have to take the carb off. Hook it up to a 12 volt battery and see how much it extends. The manual doesn't tell you how long it takes to retract, it only gives approx time to extend and a length that it should extend to.

I have tested a few of these (for hard to start dead cold) and never really paid too much attention to how long it takes for one to retract, only that it extended a certain amount. But I am pretty sure that it takes a fair amount of time for it to retract...I just cant remember. This was only a theory I had to explain the hot start problem.

The manual I have is for good for up to a 2003 model, it says the plunger should extend 4-5mm (0.16-.20") in 5 minutes. The 2003 model has Prime start P/N 65W-14380-20 and your engine has the same Part number prime start thermovalve.


As for heat soaking,I am not convinced of that at all, especially operating up here where we are. You could test that theory out fairly easy. Get the engine up to temperature and let it sit for the 30 minutes or so and if it does not start, then take the drain screw out of the carb bowl (small slotted head brass screw) and see if there is fuel left in the bowl. If there is, there is no reason for it not to start in a pull or two. If there is no fuel...then you found your problem.


Yam, this engine does not have emergency valve..

[TownsendsFJR1300]

that video was not on a 4 stroke, and I do not know how far the F25 PS unit should extend, but my thoughts are as long as it extends it should be working..

The point was to show an idea of what movement, IF ANY, should be happening..

Whether it be a 2 or 4 stroke,,

[99yam40]

well looks like you will need to figure out if it is a lack of fuel or too much fuel keeping it from starting after a 30 min set.

I would think that if it was just a lack of fuel in bowl then pumping the primer ball before trying to start would help

if too much fuel then opening the throttle to let more air in to clear out the too rich fuel charge in the motor helps

[novascotia_zodiac]

well looks like you will need to figure out if it is a lack of fuel or too much fuel keeping it from starting after a 30 min set.

I would think that if it was just a lack of fuel in bowl then pumping the primer ball before trying to start would help

if too much fuel then opening the throttle to let more air in to clear out the too rich fuel charge in the motor helps

After running, then shutting off for 30 mins to 1.5 hours, It won't start unless I give it lots of throttle. Also, I can smell the gas, so likely too much fuel.

[boscoe99]

To confirm that it is too much fuel try pinching off the fuel hose and starve the motor to make it quit running? Then let it sit for the period that you are normally letting it sit when the problem shows itself.

Pump the primer ball only until it just becomes firm. Then crank the motor. Does it start right up or is it still in a no start condition?