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Honda Bf100 VTEC loosing prime, surging

C

colinbf100

New member
I have a brand new Honda bf100 Vtec and it keeps loosing prime. Prime bulb hard few hours later it’s completely soft. Runs fine until I tilt motor up out of water or I’m stopped for a bit. Motor will not start unless I prime the bulb.
 
Sounds like the check valve (anti-drainback valve) in the primer bulb is not working correctly.

Make sure the primer bulb is laying flat or tilted upward with flow direction arrow on the bulb toward the engine. You shouldn't run it with the hose routed and hanging in such a way that the flow direction arrow is pointing downward.

It could just be a faulty primer bulb but check that all connections from tank to outboard are secure.

Good luck.
 
It should stay...let's say firm instead of hard...for quite some time. Not days but hours for sure. If it goes soft every time you stop and you need to squeeze it to start up then something is definitely wrong.
 
Changed the bulb. I can pump it hard. Few minutes later it’s completely soft. Can almost hear the fuel going back down into the tank.
 
Wierd.

Make sure that the tank vent is open and is clear.

Is the bulb you used for a replacement new?

Is the flow arrow pointing away from the tank?

Are you positive that there's no leak at the motor?

Any chance that you could try a different tank?

If you're using a portable tank, take out the pickup tube and make sure it's not cracked or damaged.

It's possible that it's sucking in more air than gas from somewhere. You may need to try the smoke test on the hose and fittings.

Some people use a clear section of hose to check for air bubbles but I just use a smoke machine. I used to use a cigarette but don't smoke anymore.

You stumped me on this one.
 
Tank is built into the boat. Brand new bulb. Arrow is pointing up from tank. I have no idea. I’m starting to think it’s an issue with the motor
 
Well, you may be right that the issue is motor side.

But, usually, if there's a problem with the outboard as in a leak somewhere, the bulb never really gets hard so I'm still suspicious of the problem being on the "suction side".

This is where I would run it on a portable tank to see what it does. But if you don't have one or can't borrow one that's a tough spot.
 
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