To many squeezing of primer bulb

**team supra** · 08-30-2025, 05:58 PM

Took boat out today first time in three months it has a 2018 mercury OptiMaxx 300 XS. did not follow proper instructions on how to prime the boat just kept on squeezing hoping Bob would get firm notice the gas smell took the boat out ran kinda rough seemed like it was flooded where does all that gas can go when you are squeezing primer bulb is there a relief before the EFI

**rock** · 08-31-2025, 08:48 AM

All you are doing when squeezing bulb is fulling the vst which is basically just a float bowl like on a carb. Once it starts getting firm stop. If it just keeps pumping there is likely something is the seat preventing the needle from shutting off fuel flow.

Rock

**Jim Speros** · 08-31-2025, 09:32 AM

And The vst vents into the plenum. The bypassed fuel gets dumped into the plenum intake

**pcrussell50** · 08-31-2025, 09:55 AM

Is the needle and seat in the VST serviceable and replaceable like in a carb?

-Peter

**whipper** · 09-02-2025, 11:02 PM

Originally Posted by pcrussell50

Is the needle and seat in the VST serviceable and replaceable like in a carb?

-Peter

The 2.5 promax vst is servasable. Not sure about 300xs. Probably is though. Are you having fuel issues you think or just odd squeezing so much. If your running fine then the VST is getting fuel. I dont think ive ever had a hard ball from my squeezing it. The fuel pump supply's enough fuel. The only time I prime ball is after a long winter just a bunch of times {not Hard} but it starts letting the fuel pump run a few seconds. Runs fine to max rpm.

**pcrussell50** · 09-03-2025, 12:06 AM

Originally Posted by whipper

The 2.5 promax vst is servasable. Not sure about 300xs. Probably is though. Are you having fuel issues you think or just odd squeezing so much. If your running fine then the VST is getting fuel. I dont think ive ever had a hard ball from my squeezing it. The fuel pump supply's enough fuel. The only time I prime ball is after a long winter just a bunch of times {not Hard} but it starts letting the fuel pump run a few seconds. Runs fine to max rpm.

It's not me mate. I just have carb motors, 2.4/200 and 2.0/150. I was just jumping in on this thread to educate myself a little. Thanks for your great answer!

-Peter

**billybob** · 09-03-2025, 11:07 AM

Always hold your Primer bulb vertical. All newer primer bulbs just have a ball in a cage, to open or shut off fuel supply. It should firm up in just a couple pumps, stop then & just drop in motor well or whatever.

**99fxst99** · 09-03-2025, 11:28 AM

Originally Posted by billybob

Always hold your Primer bulb vertical. All newer primer bulbs just have a ball in a cage, to open or shut off fuel supply. It should firm up in just a couple pumps, stop then & just drop in motor well or whatever.

Vertical with the flow arrow pointing up.

**skialot2** · 09-03-2025, 01:52 PM

I had a 135 Optimax when the VST is empty it takes about 20 pumps or more of the primer bulb to fill it up. They hold a good amount of fuel. Over a quart.