possible fuel line / carb question

joho5 · May 9, 2009

Ok, I just got this boat. Its a 1989 70hp Evinrude motor. It ran well before I messed with it, but was a little moody idling. I proceeded to pull the carbs (3 of them) and clean them. I just did a spray clean. They looked clean and I just sprayed out the bottom jet and all orfices I could get to...some of the fuel lines seemed a bit loose and all they had on them were zip ties.

Now it seems like its running weird when I open it up...it surges, then slows down, the goes to WOT for a sec, then boggs.

I am almost sure its the loose fuel lines, because some were too loose in my opinion. I am going to changeout the lines and get clamps and I am pretty sure thats the problem.

Could I have messed up the carb somewhere though in case the fuel lines arent the problem?

When there is 3 carbs to a motor, do they have to be adjusted at all? Or is everything fixed?

thanks

Matt

film495 · May 9, 2009

Re: possible fuel line / carb question

don't know, but if you change one thing at a time and test after any change you'll get it. Could be carb could be fuel lines, start with the easiest first, fuel line and hose clamps are not expensive; you probably want new ones anyways since ethanol is in the gas now and old lines were not made for it.

Alex1342 · May 9, 2009

Re: possible fuel line / carb question

A lot of times with my motors, when I run WOT and the engine bogs down, usually the culprit is the WOT adjustment. The sync and link adjustment that controls the butterfly valves. It's flooding out at WOT because your cam roller is being pushed beyond its range. Your WOT adjustment may need to be rolled back a lil bit.

joho5 · May 9, 2009

Re: possible fuel line / carb question

where is this adjustment? I just got this boat and up to this one, the biggest motor I have worked on is a 25hp...the butterfly valves should be able to handle being open all the way at WOT though correct?

joho5 · May 9, 2009

Re: possible fuel line / carb question

also, I just noticed something. There is a hose that connects to the very bottom of the intake manifolt and then attaches to the silencer. I am sure its purpose is to intake air...well I didnt attach this back by accident, so that little hose was connected to the manifold inside the cowling but just dangling down and not attached to the silencer. Could it have been choked out?

I guess I will install the new hoses and reattach this and see if the problem fixes...

thanks

Alex1342 · May 10, 2009

Re: possible fuel line / carb question

You reach your recommended WOT setting at full throttle. But at full throttle, you can still manually push down your throttle linkage on your carbs all the way down with your hands which in turn would flood your motor out.

The WOT adjustment is the throttle stop screw. Located behind the throttle linkage body which is underneath where your spark advance rod is. This is usually the setup of the motors I touch. 55HP and 70 HP Johnsons. It will be a screw held by a nut and then a stop to the right.

If you choose to do this. With the motor not running, open it up wide open. Look to the side of your carbs for the linkage that turns with your butterfly valves. The "posts" should be perfectly vertical. If they are turned too far counter clockwise, you might be flooding out at WOT.

Loosen the nut for the throttle stop screw, and turn the screw counter clockwise until you get the posts on the side of the carbs vertical. Note this is done with the motor at full throttle and not running.

Hope this helps. And your intake manifold hose issue, not being connected to the air silencer wouldnt be choking it rather not enough.

tashasdaddy · May 10, 2009

Re: possible fuel line / carb question

it is very easy, motor not running, to put the control in forward and WOT. look in to carbs, if the butterflies are going past horizonal, you need to adjust them.

now my question. did you remove the jets and clean them? read the TOP SECRET FILE, your jets are fixed so there are no adjustments. i suggest replacing all fuel lines, from tank to carbs, with alcohol resistant fuel lines. most likely you are sucking air.

is the vent open on the fuel tank?

joho5 · May 10, 2009

Re: possible fuel line / carb question

well its a bass boat and I dont know where the vent is...its a built in metal tank. Its not a portable.

Where is the vent at?

thanks

Matt

tashasdaddy · May 10, 2009

Re: possible fuel line / carb question

should be above the rub rail, near the filler, on could be a combo filler, vent.

crxess · May 10, 2009

Re: possible fuel line / carb question

joho5 said:
well its a bass boat and I dont know where the vent is...its a built in metal tank. Its not a portable.

Where is the vent at?

thanks

Matt

Look on the sides of the boat. Should be a small through hull fitting (1" or so) with a screen on the opening.

Mas · May 10, 2009

Re: possible fuel line / carb question

If you use zip ties on your fuel lines, make sure you use factory or high quality ones for this. Each are made for a specific line size by having a rigid curved portion to ensure even clamping thus preventing air entry.

MAS

joho5 · May 10, 2009

Re: possible fuel line / carb question

Well, the butterflys are going past horizontal, so that is probably a problem. On bass boats, do you normally have to manually vent the gas tank every time?

I will replace fuel lines and adjust the butterfly valves and see what happens.

thanks

Matt

tashasdaddy · May 10, 2009

Re: possible fuel line / carb question

critters love to get into vent lines a make homes, blocking the vent.

Alex1342 · May 10, 2009

Re: possible fuel line / carb question

spider eggs

joho5 · May 10, 2009

Re: possible fuel line / carb question

ok I see where the vent is and I havent checked it, but I did just now get back from lake testing the motor after changing the gas lines.

It still is inconsistent. about 40 percent of the time I ran it today it ran good, but the other 60, it wasnt getting up to the high rpms and still bogging up and down.

1 thing I could do to make it run consistent is hold down the primer button on the key. as soon as I would let off, though it would go back to running bad.

could this be a clogged fuel filter possibly? fuel pump? still an air leak somewhere, I was hoping the primer butting thing would be a clue that you guys might be able to figure this out.

in the meantime I will check the vent line and fuel filter.

thanks guys

joho5 · May 10, 2009

Re: possible fuel line / carb question

well a little more info for you guys. I pulled the fuel pump to check out all the fuel lines underneath...the fuel pump has a 4 prong pump that wasnt hooked up...I see the other side of the pump, but for some reason it wasnt hooked up.

Is that a problem and what is electrical on the fuel pump?

also when I pump the bulb it doesnt pump well, it kinda seems flat, then gets firm sometimes, then a few seconds later, its back flat again.

the fuel filter is fine, because I inplugged it from the fuel pump and pumped the bulb and it spit fuel out fine with ease.

I doubt there is anything in the vent of the gas tank, because its a straight rubber hose and there is a screen on the outside of the hull.

any ideas or things to check, please shoot them my way.

TimmyC · May 10, 2009

Re: possible fuel line / carb question

your fuel pump could be the problem, try running it and have a buddy pump it as you are running to see if it is the fuel pump or it could be a bad bulb.

joho5 · May 10, 2009

Re: possible fuel line / carb question

when i was hitting the primer it would go normal as long as i was pushing it or holding it down.

it is a vro pump and the person that had it before me cut the oil line and now i just premix.

I have researched and read some bad things about the vro pump and how some people just get a normal $35 fuel pump.

I would love to do that...what fuel pump would go with the motor though.

its a 1989 Evinrude 70hp motor.

TimmyC · May 10, 2009

Re: possible fuel line / carb question

i dont really know what other types of fuel pumps that your engine would use, but I have been looking into it and the vro pumps are around $360.
I have a 150 gt and it has one, I premix my oil also. I was told that after running a engine with the oil side disconnected that it will mess the pump up after a couple of yrs.

I have been having probs with my engine to and thought that it was my fuel pump but I done what I told you and their was no change.

It really sounds like to me that your fuel pump is bad.

Alex1342 · May 10, 2009

Re: possible fuel line / carb question

Usually when you have to hold down the primer to keep it running, its a carb issue. If you have pump the bulb, its a fuel pump or bulb issue. Seems to me you have both.

possible fuel line / carb question

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