engine is sucking fuel bulb closed?

[stackz]

ok, its my neighbor's boat.

its a 1986 2-stroke v6 engine. he told me its a 175hp engine with 150hp carbs on it.

anyway, at full throttle for an extended time the engine will bog down and when you go back to look, it's pretty much sucked the fuel bulb completely closed.

whats been done
helped him do maintainance last year and thats when the problem surfaced. I cleaned out his carbs for him and pretty much all the jets were clogged with grime. I dont understand how it actually cranked and ran as good as it did honestly. cleaned them out and now he's got another 500rpm on the top end as well as picked up an extra 8mph (gps readings).

what I think is happening
I'm thinking that now that the engine can properly pull fuel, that its basically sucking the fuel bowls dry in the carb and then pulling a vacuum on the fuel line which is sucking the fuel bulb dry.

when it bogs down we just slow down to float and I work the fuel bulb to get it to open back up and then I can literally squeeze it like if you're priming the engine for a couple times before it completely firms back up. this is why I'm thinking its sucking the fuel bulbs dry.

what can be done?
he says that when he put the engine together his guy told him all the carbs are the same on the different size engines? as far as I'm concerned, coming from the cars....the bigger the engine, the bigger the carb it needs, or at least the bigger jets it needs so it doesnt run lean, etc.

am I right or wrong and what can be done to remedy this problem one way or the other?

We went with larger fuel line than what he was running in the past already.

 

[rodbolt]

Re: engine is sucking fuel bulb closed?

all wrong
means the engine is doing what it was designed to do.
also means between the fuel primer and the liquid in the tank you have a restriction or the tank cannot vent.
very very simple.
keep running it like that and you can post about low compression and detonated pistons.

 

[stackz]

Re: engine is sucking fuel bulb closed?

yeah, dont want to post about low compression or detonation lol.

The fuel line is 100% new from the carbs to the pickup inside the tank so I'm pretty sure its not restricted.

guess its time to look at the vent setup he's got on it. I want to say we checked that though and it wasnt clogged...

hmmm

edit: wouldnt it be easy to test the clogged vent setup theory by simply unscrewing the gas tank filler cap while under full throttle? I mean at that point it would simply vent out the fuel filler cap right?

 

[99yam40]

Re: engine is sucking fuel bulb closed?

Why not just test with a pressure/vacuum gauge?

http://forums.iboats.com/showthread.php?t=283363

 

[birdseye418]

Re: engine is sucking fuel bulb closed?

tell him to look inside the tank or use a portable tank hooked directly to the motor. I had the same problem and had to have sludge / varnish flushed from in hul tank.

 

[stackz]

Re: engine is sucking fuel bulb closed?

we've had the tank out 3x earlier this summer as we cleaned it out, then replaced the fuel sender, then pulled it again to make it easier to put in the new larger fuel line.

its clean on the inside that much I can guarantee lol.

we're going to pull out the tank vent assembly completely and look it over. then hit the water and do that vacuum test procedure.

 

[Doernuth]

Re: engine is sucking fuel bulb closed?

If the tank is equipped with an anti-siphon valve check that. Also check the vent.

I would verify that the engines used the same carbs. if the carb is too small it will not run right at high rpm's

 

[rodbolt]

Re: engine is sucking fuel bulb closed?

but even with the wrong carbs it wont suck the primer flat.
only a restriction between the bulb and the liquid level in the tank,or no vent,will do that.

 

[stackz]

Re: engine is sucking fuel bulb closed?

anyone have a pic of a typical anti-siphon valve?

also, i told him about the vent possibility and we're going to look at it this weekend.

I dont remember ANYTHING honestly being attached to the fuel feed line when we ran it. in the past the only thing attached was a fuel/water separater. we bypassed that a long time ago thinking it was the problem or part of it.

we basically super simplified the fuel system to remove any variables and are at the point of scratching our heads lol.

 

[proaudioguy]

Re: engine is sucking fuel bulb closed?

Hey guys (and gals), At the risk of hijacking the thread,...... I am going through this issue as well. In my case I have an Evinrude 140. The boat sat for 3-4 years. I took it to the keys last week after replacing the perfectly good impeller with a new one. I thought I had drained the gas, but now I know there is no way I could have. The boat wouldn't get up at full throttle and ran like crap unless I held the choke in, at which point it got up on plane, and ran much better. While down there I used some Seafoam to clean up the carbs, and that seemed to make a big difference for a little while. Eventually it sucked the bulb flat. I found the pick up screen in the tank was totally covered in sediment. Cleared that and it ran again although not super great. Now I'm home, just spent about 6 hours getting the 85 gallon tank out (that's how I know I didn't have it completely drained!!!) and I'm trying to figure out the best way to CLEAN it. There is no way to get my hand or a brush in there, and it's too large to load up with a few gallons of (expensive) acetone and a bunch of BBs and slosh around, although if that's the way to go, I'll have to figure out how to make it happen. The bottom of this plastic tank is about 75-85% covered in black gak. I really appreciate someone telling me how to best CLEAN it. I can dispose of chemicals pretty easily here. I have a very large concrete area where the left over wash out can evaporate dry and I have no public drains.

Additional information, I purchased new 3/8" fuel line, and I intend to replace the fuel filter holder (not just the filter itself, but the entire part).

I've found a lot of great info here over the last week while trying to sort this out. Thanks to you guys I still have a functioning VRO having heard they were problematic. I nearly got rid of it in favor of premixing, but clearly it's working or it wouldn't have sucked the primer bulb flat.

 

[cwilt]

Re: engine is sucking fuel bulb closed?

just to throw my two cents in......i replaced my primer bulb a couple of months ago because it was leaking and after i replaced it the new bulb started to do the same thing, the old bulb never had the sucking in problem ....i think that the fuel reacted with plastic/rubber bulb. ruined my day of fishing. so i bought another one (which was more expensive) and never had a problem since. i am not telling you that this is your problem, but just what i have experienced..good luck

 

[calboats]

Re: engine is sucking fuel bulb closed?

Another thing is checking the primer bulb for pinhole leaks! I just put a 12volt fuel pump on my Evinrude 50, with the screw on fuel/water seperator and regulator. At first it looked like it wasn't going to work right, but finally found the problem, read on.

By the way, I keyed the motor fuel delivery requirements to the pump size. In my case it used a Mr Gasket #42 S -- 4 psi. and 42 gph max - with a regulator to smooth the flow, not restrict it. Smaller pump is used with the stock one, don't want to overpower that part of the system, just help the three tanks keep pressure up. So far, a much better fuel delivery system seems to me. Good see-through kevlar (?-really tough) reinforced and ethanol proof fuel hoses, so I can keep track. mounted the pump down on the floor, at the 45 deg. angle in the info. sheet, after the tank selector, and before the screw on filter. yeah, it pumps just a touch more than stock but within reason -- just keep a sharp eye on using the pump on/off switch for safety. You can hear the pump with the motor off, so I feel safe to manually control this, -- and the motor will work with it off -- but it's a nice back up touch.

The original Sea Sense primer bulb felt fine -- maybe a touch spongy, but not noticable as a problem -- until I got the power fuel pump hooked up. Then when I shut off the motor, as I reached to shut off the pump, I saw a pinhole stream of gas from the primer bulb. The electric showed it up, pinched the bulb in that area and the bulb split 1/2 inch, ooops. Got a new Moeller bulb last week and the whole system works waaay better. So, beware older primer bulbs, maybe not a Sea Sense ( Bi-Mart) one, and remember to change them yearly or so, if in the sun a lot.

Best wishes, Cal

 

[Old Crow]

Re: engine is sucking fuel bulb closed?

Your problem is from the bulb to the tank.
You replaced the line, did it get kinked or pinched off when replacing it?
Did the fuel tank get placed on top when reinstalling?

You installed new fuel line. Where did you get it? I've seen alcohol in fuel eat cheap Walmart fuel line and plug a line.

I'd check the valve on the suction side of the bulb, bet it's full of junk.

 

[calboats]

Re: engine is sucking fuel bulb closed?

Yeah, on the fuel line being more resistant than original equipment, or should be. Don't know the brand name, but there is a colored but transparent ethanol proof fuel line, (coastie cert.) that has a nylon or kevlar super tough web of reinforcing threads, maybe NAPA parts has it. My source is a wholesaler, so I'm not sure of other vendors.

I use it on my motorcycles too, as it needs no fuel line clamps, they say, but I added them anyhow -- cheap insurance. Great stuff, you can see the fuel flow anytime, watch the hand or power pump work to fill the line, see any air bubbles, etc.

good luck, Cal

 

[rodbolt]

Re: engine is sucking fuel bulb closed?

if the line is under the deck it must be type a1.
b1 or b2 is not rated for under deck use.
electric fuel pumps are NOT certified unless its equipped with a shut off device in case of engine stoppage.
the above posters fuel system is a bomb waiting and NOT compliant with USCG and certain state regulations.

 

[proaudioguy]

Re: engine is sucking fuel bulb closed?

if the line is under the deck it must be type a1.
b1 or b2 is not rated for under deck use.
electric fuel pumps are NOT certified unless its equipped with a shut off device in case of engine stoppage.
the above posters fuel system is a bomb waiting and NOT compliant with USCG and certain state regulations.

I picked up fuel line from Advanced Auto Parts. This stuff is way heavier than the gray stuff Wal-mart sells for boats. It's quite similar to what I used to use on old cars. It appears to have an inside and outside layer with a weave sandwiched in between. It's pretty much the same construction as the old stuff. The only thing that concerns me is that it's about half the wall thickness of the old fuel line. Maybe not quite half. I don't know if the old line was overkill or the new line is just not even close to good enough. We won't be using ethanol at all. Your thoughts?

 

[rodbolt]

Re: engine is sucking fuel bulb closed?

dunno
IF its marine rated for underdeck use it will be marked type A1 the newer line with low permeability has a slightly diferent marking that I cant remember.
the USCG site has it.
but an electric pump wired to the key switch or an on/off switch is NOT USCG compliant.

 

[proaudioguy]

Re: engine is sucking fuel bulb closed?

I'm not sure who you are replying to. In my case even the old line has no such markings (A1, A2, B1, B2) perhaps it's because it's for an outboard and the boat was built in the 80s. I read a very long explanation last night that stated the laws regarding use of those lines applies to inboards only, but advised all boat builders follow them just to be safe. Since the boat is an 88, I'm not sure that company was complying with rules that didn't even apply to them back then.

I'm going to start a new thread with lots of questions.