Yamaha 40 Primer

david18

Seaman Apprentice
Joined
Jul 22, 2005
Messages
35
I am working on a 2005 Yamaha 40 horse 2 stroke. It runs great but is hard to start. I am looking at the primer device located on the middle carb. I checked the blue wire for power when the key is pressed and I get nothing. I removed the primer and went straight to the battery with the blue and black wire and the plunger doesn't move. I don't change parts until I understand the problem.
Should the plunger move when the key is pressed? Is there an automatic mode for this thing? Thanks for the help.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha 40 Primer

It is called Prime Start Enrichment System or Prime Start System, do a forum search on it and you will find some good info on it.
I too, did not understand how it worked and Rodbolt helped me out.
I even studied it trying to understand the passages and flows flow paths of liquid fuel and vapor and tried drawing sketches of what I thought.
Rodbolt told me I was thinking to hard. But you can find all kinds of info when you look.

See if this helps you understand the system.
http://forums.iboats.com/showthread.php?t=357552
 

serenaa

Recruit
Joined
Mar 16, 2011
Messages
1
Re: Yamaha 40 Primer

Hello,
The Primer bulb leading to the Racor from the fuel tank will not stay primed. The one from the Racor to the engine will stay primed. I noticed this because when I went out in the boat today all it would do is go slow ahead. Whenever I tried to go on plane there was not enough power (rpm's would only hit 24 or 25 hundred) and it just sounded like all cylinders were not firing - it just sounded bad.

thanks!!

__________________
used car vancouver
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha 40 Primer

Serenaa,
Start your own thread with all you motor info and ask you questions
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Re: Yamaha 40 Primer

I am working on a 2005 Yamaha 40 horse 2 stroke. It runs great but is hard to start. I am looking at the primer device located on the middle carb. I checked the blue wire for power when the key is pressed and I get nothing. I removed the primer and went straight to the battery with the blue and black wire and the plunger doesn't move. I don't change parts until I understand the problem.
Should the plunger move when the key is pressed? Is there an automatic mode for this thing? Thanks for the help.
Prime start is totally automatic, turn red plastic lever to emergency start position and try to start the motor. If it starts in that position then that might confirm a problem with the primestart system. If motor still won't start, then maybe another problem. Good Luck1
 
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