2006 Mercury 8hp 4 stroke

"Hi guys. I have a question th

"Hi guys. I have a question that I hope someone can shed some light on for me. I have a new 2006 Mercury 8hp 4 stroke that I run on my boat as a kicker. Upon purchase, I plumbed the fuel line to the kicker from my water/fuel seperator. I had an anti syphon valve in the line as well. The motor would die about avery ten minutes or so. IF I ran the motor on the 3 gallon can from Mercury it would run fine. So I removed the syphon valve from the seperator and that didn't help. Next I bipassed the seperator and ran the motor directly from the boat's fuel tank. That corrected the problem. My question is: has anyone else had this problem and are the fuel pumps in the smaller motors not strong enough to suck the fuel through the seperator? Thanks for any info provided."

"Doug, I'm not familiar wi

"Doug, I'm not familiar with 4 stroke motors at all - but have the collection of service manuals.

I took a look and the fuel pump on your motor should produce between 3 and 6psi depending on whether it's at idle or full throttle.

Compared to say a 90 horse (which would normally be on a built in tank), the 90 produces a minimum of 7 psi at idle.

So perhaps your motor simply does not develop enough pressure to suck the gas through your separator - do you have literature or specs on it?? does it specify what kind of pressure it needs to get gas through it?

Just guessing here, but since your motor appears to function normally otherwise, perhaps you are simply going to have to bypass your separator or find one with a high enough flow rate that your little engine can pull through it...."

"Graham, my theory is: since t

"Graham, my theory is: since this is a 4 stroke it turns half the rpm's of the 2 stroke so at trolling speed maybe the motor doesn't develop enough suction from the fuel pump to draw fuel through the seperator. Since I plumbed the motor directly from the fuel tank it runs fine."

"Graham,

Similar problem he

"Graham,

Similar problem here, but related to starting the 8.0 when it is cold. With it plumbed through the water seperator it seems to be a magical trick to get the thing started. Pump the ball (it doesn't seem to be filling), choke, and press the front gizmo several times. Then pull, and pull, and pull. If lucky it starts on the 7th or 8th pull and then more magic required to keep it running between the choke and the gizmo.

When plumbed directly to the auxuliiary tank, 1st pull, no magic and the little guy seems to run fine. Similar issues for you?"

"Yes, I had similar problems s

"Yes, I had similar problems starting the motor when it was plumbed to the separator. Since plumbing it directly from the tank no more problems. One other trick I have learned is to push in the shift release button on the side and advance the throttle a little more. The motor starts better this way when it is warm."