prime starter

[maco]

How can I test the prime starter to see if this unit is functioning? This is on an '03 40hp. I've been through all 3 carbs. cleaned and compressed air the whole 9yards. The motor will not idle very long but runs well at WOT. I have to baby it to reach 1000rpms and then she'll run. It is hard to start, which leds me to think that there may be a problem with the prime start. I read that the prime start shuts down at about half throttle. I don't think mine is working at all. Can any one help? Maco

[dorf]

Just my 2 cents but it sounds like a restriction in fuel supply problem,... filters, anti-siiphon valve in fuel tank, hoses or even vent, etc. Or even idle speed setting low......

PrimeStart increases fuel flow then shuts off.

[99yam40]

look at this and see if it will help you understand the prime start system.
You can also do a forum search on prime start to read more about it

Rodbolt and Yamaha Prime Start - Awesome - iboats Boating Forums

[dorf]

Yeah...Service manual !!!
Clymer Manual great. Lots of pictures and desriptions, better than factory. IMHO.

Cheers !!!

[maco]

Thanks for the response! Believe it or not I'm thinking fuel line also. I should have checked this sooner but I just didn't think I would have this problem so soon. With all the talk about ethanol, I assumed the worst (inside carbs). I watched the fuel filter slowly fill with air as my motor ran yesterday and then the motor shut down. I seem to have an intermiting problem with my prime bulb. It will pump hard sometimes other times it wont. I'm going to get a new bulb today and try that route. Thanks again. maco

[dorf]

I've had an on going problem with Yamaha Primer Bulbs. I've tried numerous after market ones also.

I finally purchased an Evinrude/Johnnson /Bombardier --0775639--that seems to work great.

Check all lines and clamps.

Let us know what fixed the problem.......

[maco]

YAHTEEZ!!!! New prime bulb. The motor ran for about 5 minutes after installation, then shut off. The filter had air. I pumped the bulb up again and it ran for about 15 minutes, then I shut her down. I didn't see any more air. It did idle a little rough but it took gas. Probably because I tinkered with the carbs. I can't wait to put it back in the water to see how well it will run under stress, wot, whole shot, etc and then return back to idle without shutting down. Thanks for sharing your knowledge!!!! I'm still curious about the anti-siiphon valve mentioned thats in the gas tank? Because air came back once, I'm still wondering what I may have in store for me. Again thanks for sharing.

maco

[dorf]

Anti-siphon valve is a ball-with seat affair(prevents drainage and siphoning of fuel from tank when engine is not operating) that comes off seat when the fuel pump is sucking fuel.

If it sticks----no fuel to the engine untill the suction increases.

It is located at the output of an on board fuel tank and is easily removed.

[maco]

My motor has improved 90% since putting on the new primer bulb but it is still sluggish when I do a whole shot. It has to reach 1000 to 1200 rpms before it will run wot. Could this be a symptom of the anti-siphon valve or maybe something else? Thanks in advance and in the past!!

maco

[dorf]

I'm certiantly no expert but it seems like if the primer bulb helped your problem must be fuel related.

I don't know what kind of set up you have but it is very easy to punch out the valve/bulb in the fuel outlet.
Take off the outlet valve from the fuel tank, put in a vise, use a punch and wholla.....it is gone.Re-install If no improve ment .

[maco]

I have a 18 gal. tank that fits under the center console of a 19' carolina skiff. Hooked up to an 03 40 hp.

[dorf]

Un screw the fitting where the fuel exits the tank. In that fitting is the anti-siphon valve. ... I'll bet.......

Let us know what you find....and what happens after you remove it.