1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Morning everyone,

I am stumped here, and have read the forums over and over, yet no avail on my issue. Any help would be appreciated.

I have a 1986 Four Winns Liberator with the Mercruiser 350 and Alpha outdrive. (Motor model # MCM 260.) The issue left to solve is this-

The boat runs great at WOT for about 4-6 minutes and then acts to the degree the fuel line is pinched off. If you throttle back quickly it seems to recover, but then doesn?t want to run WOT again for a while. (Assume it is cleaning fuel out of carb bowl and then refilling?.) So I have replaced the fuel/water separator filter, the filter that goes up by the carb and the check valve on the tank. Also (before 3rd round of filter changes) cleaned the fuel tank out. It had a nice nasty layer of ?crud? on bottom which I got out, and then blew the lines clean (really sucked fuel out of them) until the fuel coming out was clean. All I can figure out is that the fuel pump is bad, not sure what else is left to R&R! Any suggestions or comment s? I am concerned about spending $150 on a fuel pump to find out that is not the core of the problem. Also I checked all fuel lines and they appear good. When filling boat the vapors come out the fuel vent tube release (near filler cap) so I assume that line isn?t clogged either. Do I spend the money on a fuel pump or does anyone else have any ideas?

Thanks in advance for the help, these forums are great.

P.S.- Mercruiser parts maybe expensive, however their dealers are great people. I can't say how much help they are, and actually want to listen to questions, not just sell items off their shelf!

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

i would test the fuel presser and maybe the float level

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Thanks for the help.

A few questions-

1. What are you defining as float level?

2. What is the actual fuel pressue required?

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

1. What are you defining as float level?

2. What is the actual fuel pressue required?

Click to expand...

Ayuh,... 1,.. That's the carb's float level in the carb...
2,.. 4 to 6psi for a Carb...

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Sorry should have been more accurate. What level is defined as "correct" for the float? Are you referring to it sticking or being inop, etc?

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

What level is defined as "correct" for the float? Are you referring to it sticking or being inop, etc?

Click to expand...

Ayuh,... All of the above,....
The required Float Level is listed in the manual, or in a carb Rebuild Kit,....
You haven't said whether it still has the original Rochester, or a Merc./ Weber, or,.?.?.?.?.

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

I assume you are askign about Manufactor of fuel pump, that I don't know. it is coming off tonight and I will be able to tell yas. The more I read, the more I think a fuel pump replacement is the answer to the problem.

Does anyone suggest a true Mercruiser pump or are aftermarket (marine) pumps worth the $20 saved?

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

manufacture of your carb? pull the line out b4 it enters the seperator insert line in gatorade or water bottel have someone crank the engine and watch fuel flow. Should be stady, like a drinking fountain no bursts. do the same b4 it enters carb. I have also read that fuel lines can blister inside and cause the "pinching" you refer to at higher rpm, this would be the line coming from your tank to the pump. the vacume created by the pump colapses the line on itself. rent fuel pressure tester at autozone for free, hook it up inline to you carb run engine and record readin 4-6psi i beleive. had this problem pin hole on the fuel line b4 the pump under the clamp no fuel leak was hard to find. was suking air into the system causing engine to sputter, die, hard to start after.

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Update:

1. Installed new fuel pump, boat ran better (more RPMs and speed) but problem still existed further down the water way. (Ran about 2-3 minutes longer)

2. Hooked up separate fuel source to fuel/water separator barbed connector (used 2 gallon gas tank) - boat ran perfect! Couldn?t off been happier, so know problem is from fuel line back into tank.

3. Got it home, pulled all fuel from tank, checked fuel pick up, screen is clean. Fuel coming out looks good to!

4. Checked vent line, free and clear!

Now very puzzled as the tank has small amount of ?junk? particle(s) here and there but should not clog up or stop fuel pick up in tank to make boat stall out. Thinking that the hose (rubber, double walled) between tank (check valve actually) and fuel water separator may be collapsing under pressure. The new pump really ?sucks?!

Open to any ideas any one may have.

Note- I noticed a seal that goes between engine compartment and main part of boat that fuel lines run through, are they a onetime use deal? I am contemplating replacing the fuel hose to see if that solves the problem. (Nothing left to replace, other than that???)

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

You never mentioned the anti siphon valve. It's that fitting on the top of the gas tank that looks like a hose barb. Pull it out and look at it. There is a spring and check ball in it. May be clogged or sticking.

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Yeah. Your Liberator does have an "Anti-siphon" check valve in the fuel line. It's screwed into the right-angle fitting at the fuel pick up on the top of the tank.

The check ball probably has some debris in it or it's got a little corrosion etc that is making the check ball stick.


Just get another one. West Marine usually has them on the shelf. That's where I got mine.

It's aluminum so don't try to tighten it too much or it'll break off.

Cheers,


Rick

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

You could very well have old fuel lines that aren't alcohol rated. They can be turned to sponge by the alcohol...even MTBE did it. easily suckable. Any gas smell?

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Thanks for the help and suggestions. I replaced it with a brand new check valve, it was one of the first "wrenching" repairs made. The dealer said one piece of "crud" in those and you are sunk. At this time it didnt seem to make a difference. I can push fuel out of tank through the valve, so that said I know that the check valve works, and the vent hose isn't clogged. (Don't ask! )

My father in law has been a car "guru" (sp) for over 50 years, and the boat has him stumped. I can honestly say that I have never seen him not come up with some degree of repair or solution to anything. Duct tape aside we are both lost.....

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

jtybt said:

You could very well have old fuel lines that aren't alcohol rated. They can be turned to sponge by the alcohol...even MTBE did it. easily suckable. Any gas smell?

Click to expand...

Not to sound silly, but yeah the do have a slight gas smell as the fumes in the motor area do add up when pull and moving gas lines around. The line from the fuel/water seperator to the tank (really the check valve) is a very thick, if not double walled (one solid hose though) rubber hose. I cut a small piece of to get the last (old) check valve free and it was still pliable. We pressure tested it (air compressor on one side, old check valve on other) and it holds pressue.

Not to be a broken record but I am lost. It is surely a fuel delievery problem, but the only options that are left are this hose discussed here, and then tank itself!

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

You may have a defective fuel pump.

Also (before 3rd round of filter changes) cleaned the fuel tank out.

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Also, just how did you "clean out the tank"?

Before I pulled the 44 gallon tank out of my Lib, I removed the tank sender and used a clear 3/4" vinyl hose to "vacuum" out the tank with the bow up a little..... (Using a long enough hose you can get a good siphon going that will act like a vacuum)


I didn't have any "crud" in my tank at all.


Also, did you remove the fuel pickup and inspect & clean the screen?
When you remove the fitting on the tank the anti-siphon check-valve and fuel pickup line all come out together.

Once you get all that clean, try disconnecting the fuel line to the carb and crank the engine and see if you get good fuel flow from the tank thru the filter and pump..... You could use a separate tank and fuel line to the carb and run the engine (on a flush adapter) to see if the fuel pump is doing the job.

I don't know what fuel pump you have but you can go to Schucks/Kragan/Oreilly autoparts and ask to see their MASTER or Airtex catalog. Airtex makes the just about all the marine fuel pumps for the whole industry.

I was able to get the correct marine pump from them to replace my Mercruiser pump.

It was about 1/3 the price of a Mercruiser pump and was the exact replacement model.


Regards,


Rick


Oh by the way, while you're in there, replace all your flexible fuel lines with new hose from West Marine or equiv......

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Evening,

Thanks for the great and detailed response, nice to know there is some ?free? help still in the world! I will answer the questions block by block with detail hopefully that will lead to the next step, of which I hope the solution!

1. I did the same, just used a ?? ID piece of tubing to vacuum the bottom of tank. Had a red film on bottom, of which I got about 99.9% of it off/out. I cranked the trailer tongue up as high as it would go to ensure all the fuel and any debris would slide to back of tank?
2. Pulled pick up and inspected it top to bottom, clean as it can be. This really frustrated me as I thought it would be the source of my issues!

3. Ran the boat on a separate fuel source, never seen it run so good. The problem, at least in my opinion has been isolated to the line from the water/fuel separator back to the fuel tank. Next step I am planning is to replace the lines as you stated. (Only fuel line that is rubber is the line from water separator to fuel tank check valve. With the exception of the vent and fill lines which are fine?) So will replace the one rubber line that I can?t rule out as bad?..

4. Yeah I all ready bought and installed the overpriced Merc pump- stupid me. I thought that was the problem and went off on my own and made the purchase. Kicking myself for that now. Nice warm feeling knowing my $131 plus tax is pumping away!

So to summarize the next move is the fuel line replacement from the water/fuel separator to the fuel tank check valve. After that if it doesn?t work, I am seriously considering pulling the tank out and examining every darn inch of it. I am well baffled at what is wrong here???

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Yeah I all ready bought and installed the overpriced Merc pump- stupid me. I thought that was the problem and went off on my own and made the purchase. Kicking myself for that now. Nice warm feeling knowing my $131 plus tax is pumping away!

Click to expand...

Well, it's not going to kill you and you'll know better next time. That pump will last a long time, so in the grand scheme of things it's still a small price to pay to fix it!

You will want to know that you have good fuel flow from the whole thing once you replace all the fuel lines, you might use some clear line from the fitting at the carb, and run it to a container so you can see what it looks like in the line. ( I.E. Good flow, NO bubbles)

Since the fuel pump actually applies suction to the whole system from the fuel pump inlet all the way to the fuel pickup, ANY tiny little leak will introduce air into the system.

I ended up replacing my anti-siphon valve because broke it off tightening it too tight. I noticed that it was cracked before I broke it off. It might have happened right there ot it may have been that way for a while. Either way it would have sucked a little air into the system.

Also, you could have a similar problem with the fuel pickup tube........Although it's a LOT harder to crack it since it's galvanized steel.

Don't forget to post a picture of your Liberator!


Always like seeing another Lib!!

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

Thanks for the help on the subject there. If my hair wasnt as short as it is, I'd be ripping it out. The crack in the fuel pick up is a logical idea I never considered. It does exhibit the symptoms with a full tank of fuel or 1/4 tank so you have me wondering now.

The clear plastic tube is on my list to try next, as I purchased some over the weekend. I am interested in seeing if it stalls and when it does what is exactly in the line. Adavance Auto sells rubber gas line tubbing for about $2/foot so I will be investing in about 36" of that to try also.

Here is hoping!

Re: 1986 Mercruiser 350 Fuel Problem? (86 Liberator 211 Four Winns Boat)

I just got the stuff you can get at Home Depot. It's fairly thick-walled and you can also get a brass hose-bib that fits too. (Make sure you use mini clamps or it might leak)

If you have a tiny air leak, you'll really see the bubbles!