Hello everyone. Have read many threads on this topic and there are just as many opinions. Fact is it gets abit confusing and I am hoping you can clear the mud for me! 
I try to sort through the logic but I'm not overly knowledgable on the workings of engines.
I have a 3L 135hp Mercruiser I/O and the kicker is a 4 stroke 9.8hp Tohatsu. I want to run the fuel for the kicker off the main fuel tank (I understand the risk if the fuel fowls both engines are pooched when only using 1 fuel source). No real room for a separate gas tank in the boat along with the family and all the gear (2007 18' Maxum bowrider). I have installed a separater that has 2 outlets. 1 goes directly to the main I/O and the other will run to the kicker. They put on a hose to go to the kicker that has a bulb after leaving the separater.
By having a bulb going to the kicker does this solve possible problems of the main motor sucking air from the kicker? I read in a post the bulb must remain with the outflow end higher than the inflow end for the ball valve to function correctly?
Is it possible that the kicker can suck air from the I/O rendering the main engine non-functioning?
Is all of this only an issue if I would run both engines at the same time? I'm not sure when I would actually do this (run both motors at the same time). The kicker is 99% back up to the I/O (ideally it would never actually be used as a back-up). 1% of the time I will be using it to troll for salmon. If I'm running to a new location the kicker would be off and the main engine would be used, then turned off again. Kicker re-started to again troll. Any problems fuel-wise with this scenario? Each time the kicker is re-started would the bulb need to be primed? (the bulb is with the engine compartment).
I plan to run the fuel after the bulb through the hull using a brass bulkhead fitting, then to the engine using the standard external clip on attachment. I assume the bulkhead fitting plays no role in any of this?
Thanks for your input and time,
Ken
I try to sort through the logic but I'm not overly knowledgable on the workings of engines.I have a 3L 135hp Mercruiser I/O and the kicker is a 4 stroke 9.8hp Tohatsu. I want to run the fuel for the kicker off the main fuel tank (I understand the risk if the fuel fowls both engines are pooched when only using 1 fuel source). No real room for a separate gas tank in the boat along with the family and all the gear (2007 18' Maxum bowrider). I have installed a separater that has 2 outlets. 1 goes directly to the main I/O and the other will run to the kicker. They put on a hose to go to the kicker that has a bulb after leaving the separater.
By having a bulb going to the kicker does this solve possible problems of the main motor sucking air from the kicker? I read in a post the bulb must remain with the outflow end higher than the inflow end for the ball valve to function correctly?
Is it possible that the kicker can suck air from the I/O rendering the main engine non-functioning?
Is all of this only an issue if I would run both engines at the same time? I'm not sure when I would actually do this (run both motors at the same time). The kicker is 99% back up to the I/O (ideally it would never actually be used as a back-up). 1% of the time I will be using it to troll for salmon. If I'm running to a new location the kicker would be off and the main engine would be used, then turned off again. Kicker re-started to again troll. Any problems fuel-wise with this scenario? Each time the kicker is re-started would the bulb need to be primed? (the bulb is with the engine compartment).
I plan to run the fuel after the bulb through the hull using a brass bulkhead fitting, then to the engine using the standard external clip on attachment. I assume the bulkhead fitting plays no role in any of this?
Thanks for your input and time,
Ken