Help me out, Kids want to go tubing!

[zazoos]

Need a bit of help.
<o> </o>
Here are the problems:

• Mechanical fuel pump with two fuel filters. One before the pump and one afterwards. The one before the pump has fuel but it is bubbling. The one after the pump is practically dry. Fuel pump is new and just in case of a weak diaphragm I replaced it with another new one. Generally occurs after twenty minutes of run time.
• Replaced mechanical pump with electric pump rated for 6 psi and every thing runs great for about 3 weekends. Still running two fuel filters. One before the pump and one after. The filter after the pump is dry and the one prior is full. Not for sure what the problem is, but I still have the mechanical fuel pump on the boat so I reroute the lines back to it, just to try and finish enjoying the weekend. The problem with fuel bubbling in the first filter returns. So I put the electric pump in line with the mechanical but no luck. I pulled the inline filters in the Holley 750 and they are clean as a whistle.
• While limping back to the dock (intermitting getting to plane out) motor begins running rough, won’t idle and the oil looks like a milkshake.

<o> </o>
Here are the facts:

• Gate valve open fully since day one. (didn’t know I should adjust it)
• Used a turkey pan (didn’t know I wasn’t suppose too) Eldebrock Torker 455 intake
• Water temp gauge broken (so I have no idea what the motor temp was, boat is a project.. aren’t they all)
• 455 engine with Indmar log exhaust manifolds.
• All new plumbing hoses with excellent water flow when on trailer using garden hose.
• <st1:City><st1lace>Berkley</st1lace></st1:City> pump
• I have since take the motor out and tore it apart, but cannot figure out exactly where the problem occurred.
• Fuel tanks have been cut in half cleaned and welded up this summer.
• Generally never turned more than 3500 rpm.

<o> </o>
Here are the questions:

• Do electric fuel pumps get weak diaphragms or do they just quit working?
• The turkey pan looks fine, would it be evident if it was the problem? Such as a rip?
• What temp does vapor lock occur? The engine never seemed all that hot.
• Any suggestions.

Thanks for the help.
Trent

[Charger200]

not a mechanic but i am a plumber..The pump might not be getting enough gas be it the filter causeing restricted suction or the pump may be too far from the pickup.

also pump may need to be primed for it to work. it might have a minor air lock that it can not over come and it may continue as a result or restriction upstream of the pump once again the filter distance pump is from tank or debris in the line which could just be scum from gas sitting there over time

Pump may be too high powerd for the application

[Noah1]

I would replace both filters. In your gas tank there is a screen filter at the end of the pick up tube. This could be plug or part way plug. Also check your gas lines. If your line is cracked, you will be sucking air & not gas.
Hope this Helps

[stvhelm]

you should investigate the milkshake oil. that means water is getting in the engine. clear that up first then see if it runs better. your fuel system just may be ok.

[trashytrihull]

if i were treating this like a car my first answer would be is the tank vented? are you pulling a vaccum in the tank after twenty mins or so? leave the filler cap off and retry

check for pinholes before the first bubbling filter, and check especially for holes in pickup tube in fuel cell or tank.


where was the electric pump located? most 12v car holley or autozone pumps will get hot and cavitate first(not pump well) but usually stop working all together.

never really had too many probs with vapor lock make sure all fuel lines are cool and away from exhaust. (did you try taking line loose from carb when it acted up?)


milkshake is scary, but fuel system should be a simple fix.

[OldSleekOlds]

Need a bit of help.
<o> </o>
Here are the problems:

• Mechanical fuel pump with two fuel filters. One before the pump and one afterwards. The one before the pump has fuel but it is bubbling. The one after the pump is practically dry. Fuel pump is new and just in case of a weak diaphragm I replaced it with another new one. Generally occurs after twenty minutes of run time.
• Replaced mechanical pump with electric pump rated for 6 psi and every thing runs great for about 3 weekends. Still running two fuel filters. One before the pump and one after. The filter after the pump is dry and the one prior is full. Not for sure what the problem is, but I still have the mechanical fuel pump on the boat so I reroute the lines back to it, just to try and finish enjoying the weekend. The problem with fuel bubbling in the first filter returns. So I put the electric pump in line with the mechanical but no luck. I pulled the inline filters in the Holley 750 and they are clean as a whistle.
• While limping back to the dock (intermitting getting to plane out) motor begins running rough, won’t idle and the oil looks like a milkshake.

<o> </o>
Here are the facts:

• Gate valve open fully since day one. (didn’t know I should adjust it)
• Used a turkey pan (didn’t know I wasn’t suppose too) Eldebrock Torker 455 intake
• Water temp gauge broken (so I have no idea what the motor temp was, boat is a project.. aren’t they all)
• 455 engine with Indmar log exhaust manifolds.
• All new plumbing hoses with excellent water flow when on trailer using garden hose.
• <st1:City><st1lace>Berkley</st1lace></st1:City> pump
• I have since take the motor out and tore it apart, but cannot figure out exactly where the problem occurred.
• Fuel tanks have been cut in half cleaned and welded up this summer.
• Generally never turned more than 3500 rpm.

<o> </o>
Here are the questions:

• Do electric fuel pumps get weak diaphragms or do they just quit working?
• The turkey pan looks fine, would it be evident if it was the problem? Such as a rip?
• What temp does vapor lock occur? The engine never seemed all that hot.
• Any suggestions.

Thanks for the help.
Trent

The fuel problem sounds like a tank venting issue. Find the fuel tank vent and make sure it's open (not plugged). It will be either a hose running to a fitting (through hull) or a vented cap. If it has no vent, it will act exactly like what you have.

The milky looking oil is probably from way too much pressure in the cooling system. A jet pump can put out 300+ psi. If all the water fittings are good sized and open, and the gate valve wide open, the odds are you are putting too much pressure in the cooling system. You can protect the cooling system by installing a gage to monitor the cooling water pressure in the engine. Only open the gate valve enough to maintain pressure between 8 psi - 12 psi.

I recommend a thermostat and a relief valve to control pressure. You need enough engine temp to get rid of condensation (160° - 180°).

Here's my setup.



Sounds like you're doin an awful lot of unnecessary work.

Good Luck

[wca_tim]

a waterleak in the exhaust can make it run like crap limping back to the dock as well... pressure test your exhaust system (water jackets), leaking manifolds and risers (have no idea what you have) can wreak havoc, as can leaking intake manifold if you pumped way too much water pressure into the engine... buy and install a cheap fuel pressure gauge next to the carb get your temp gauge fixed or buy a cheap automotive mechanical one for temp use. Nothing beats information when trying to figure out the first place things are running amok in a situation like yours.

I wouldn't do anything (aside from cleaning the engine thoroughly of water- change oil, remove plugs, squirt some oil in cylinders, turn it over, do it again... after manifolds are removed - it water is coming from exhaust, pummping more in while you do it won't help... ) until I was sure the cooling system was leak free and I had gauges that worked in key locations. Just my two ceonts. Hope you get it set up the way you want...