Help setting Carb Floats!

[mwinchel]

Hey there i bought a boat last year. It is 15 foot and has a merc 115 on it. Both the boat and the motor are 1971 models. The boat bogs out at wide open throttle. I am thinking that maybe the floats are not set right that is is getting to much fuel of not enough. How do i set the floats on this motor. I took that carbs the whole way off last year so that is why i am thinking i didn't get them set right. Let me know what you all think. I have good compression on all cylinders, new plugs, wires, and i re wired the entire motor because of the rotted wires. The boat runs good for what i want it to do i just want to hit wot without it bogging. My boat should fly with the big old motor. Let me know thanks a bunch for any help.

 

[j_martin]

Re: Help setting Carb Floats!

Hey there i bought a boat last year. It is 15 foot and has a merc 115 on it. Both the boat and the motor are 1971 models. The boat bogs out at wide open throttle. I am thinking that maybe the floats are not set right that is is getting to much fuel of not enough. How do i set the floats on this motor. I took that carbs the whole way off last year so that is why i am thinking i didn't get them set right. Let me know what you all think. I have good compression on all cylinders, new plugs, wires, and i re wired the entire motor because of the rotted wires. The boat runs good for what i want it to do i just want to hit wot without it bogging. My boat should fly with the big old motor. Let me know thanks a bunch for any help.

Do some more testing. Have someone squeeze the primer bulb when it's bogging down. If it picks up, it's short of fuel. If it bogs further, it's flooding. If it doesn't make any difference, the trouble is ignition.

The problem is more likely fuel supply. If the primer bulb and hose isn't stock Mercury, replace it. Check the tank vent and pickup screen. Replace the fuel filter. Put in a fuel pump kit. If the stock mercury metel bayonet fitting has been replace by an aftermarket plastic one, replace it. (experience has shown me that the aftermarket plastic fuel parts just can't deliver enough fuel to a bigish engine.

hope it helps
John

 

[Willyclay]

Re: Help setting Carb Floats!

While you have the boat in the water and are trying the fuel primer bulb test recommended by John, you can also check for clogged main carb jets. With the motor in forward gear, warm and bogging at WOT, activate the choke/primer. If the motor RPM's jump up, you probably have gunk in your main jets. Depending on the design of your motor and carbs, you may be able to clean the jets without removing them or the carbs. Good luck!

 

[j_martin]

Re: Help setting Carb Floats!

While you have the boat in the water and are trying the fuel primer bulb test recommended by John, you can also check for clogged main carb jets. With the motor in forward gear, warm and bogging at WOT, activate the choke/primer. If the motor RPM's jump up, you probably have gunk in your main jets. Depending on the design of your motor and carbs, you may be able to clean the jets without removing them or the carbs. Good luck!

If they're that bad, I'd take em off and rebuild them, because that's easier than dealing with melted pistons.

John

 

[mwinchel]

Re: Help setting Carb Floats!

I took the boat out 2 weeks ago. I had a friend pump the ball when it acted up and it did nothing different with the motor. I did replace the fuel pump ball and line when i bought the motor. I replaced it with a cheap after market one. I noticed another member said that the cheap ones are not good. Has anyone else heard of that. The ball is not hard with fuel either when i am going down the lake. I also have replaced the fuel pump diagrams and still nothing. Like i said earlier the boat goes fine just not the last inch of throttle.

 

[Laddies]

Re: Help setting Carb Floats!

Your starving the engine for fuel at high speed, clean the carbs like John said or keep running it and wonder why it's blown up. Your choice, your money

 

[jheron]

Re: Help setting Carb Floats!

I replaced it with a cheap after market one. I noticed another member said that the cheap ones are not good. Has anyone else heard of that.

I went through 2 of the aftermarket bulbs and fuel lines on my 9.8...
I didn't even try aftermarket on my 115, I bit the bullet and bought a name brand bulb and top quality lines...
Regards,
Jon

 

[ccmarsh]

Re: Help setting Carb Floats!

I just rebuilt mine as well. (Holley 2b) start your engine and let it warm up for a while. There should be a screw on the side of the primary float bowl. The fuel should just trickle out when the motor is running. Once you have accomplished that you need to adjust the needles. Start to close the needles slowly until the engine starts to die then open them up one and one half turns. Mine has two so i had to do it to both needles. Hope this helps.


Chris

 

[j_martin]

Re: Help setting Carb Floats!

I got a good deal on an XR4 because it crapped out at WOT. The aftermarket fuel line and plastic bayonet fitting were most of the problem. That engine wants more fuel (about 15 gal/hour) than yours, but the aftermarket parts are basically junk.

The primer bulb should not be hard while running. You're drawing fuel through it. It should not collapse, but it wouldn't be hard either.

Sometimes, there gets to be a little flake of something in the float bowl of the carb, and it drifts over the jets on and off. The most classic case I saw was my father in law's buick. Stalled on takeoff and wouldn't restart on several occasions. He had the carb rebuilt twice with no improvement. I checked it out, and determined it was starving, and insisted on tearing down the carb. I said if I can't find something obviously wrong, I'd buy the parts to put it back together. When I was backing out the main jet, he commented, "you don't have to do that, nobody else does." I backed it out and found a "factory installed" brass machining chip under it. That was the problem.

Another thought; if that engine has an 'Idle stabilizer" module on it, disconnect it temporarily and try it out. Sometimes they are troublesome in unpredictable ways. Good tune and adjustment make the module unneccessary.

hope it helps
John