Help me out, Kids want to go tubing!

[zazoos2]

Need a bit of help.
Here are the problems:
1. 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.
2. 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.
3. While limping back to the dock (intermitting getting to plane out) motor begins running rough, wonÂ’t idle and the oil looks like a milkshake.
Here are the facts:
1. Gate valve open fully since day one. (didnÂ’t know I should adjust it)
2. Used a turkey pan (didnÂ’t know I wasnÂ’t suppose too) Eldebrock Torker 455 intake
3. Water temp gauge broken (so I have no idea what the motor temp was, boat is a project.. arenÂ’t they all)
4. 455 engine with Indmar log exhaust manifolds.
5. All new plumbing hoses with excellent water flow when on trailer using garden hose.
6. Berkley pump
7. I have since take the motor out and tore it apart, but cannot figure out exactly where the problem occurred.
8. Fuel tanks have been cut in half cleaned and welded up this summer.
9. Generally never turned more than 3500 rpm.
Here are the questions:
1. Do electric fuel pumps get weak diaphragms or do they just quit working?
2. The turkey pan looks fine, would it be evident if it was the problem? Such as a rip?
3. What temp does vapor lock occur? The engine never seemed all that hot.
4. Any suggestions.
Thanks for the help.
Trent

[jungledave]

Vapor lock occours usually on the suction side of the fuel pump since fuel boils at a much lower temp under vacume. A fuel line too close to the exhaust manifold especially a metal line; logs usually don't get that hot. Make sure your tanks are vented. Did you make any changes to the fuel tanks or necks after you cleaned them. Open a fuel cap and see if this helps. Make sure you are not getting a leak anywhere in the line from the tank outlet to the pump. Just a few ideas. I doubt it is a fuel pum since you have tried so many.

[jetboatperformance]

Sounds to me(happens after 20 min's) like you may have tank contamination gathering in your filter or possibly on the tiny tank pick up stainer (if equipt) RE the "milkshake" often times this occurs before the lake trip when running on the hose (not always noticed right away) Always start the motor then turn on the hose Always shut the hose off before the motor! Just trying to give you possibilities here Lots of other thoughts and Ideas if you need help! Tom
BTW you mentioned "turkey pan" if your using the oem steel gasket with an after market intake it will leak period those manifolds were designed for Thick aft mkt gaskets !

[Cas]

regarding the milkshake, the 2 places to look at first are the turkey tray on the intake, as Tom said and the water pump cover. The water pump covers can and will deteriorate and let water into the engine especially with added pressure.
A few years ago, I ran into the air bubbles in the fuel thing. It turned out ro be a pin hole in the fuel line where it was connected to one of the tanks. I guess with the fuel flowing through it it would cause a vacuum and suck air. It also didn't leak because it was up high and the gas would drain away from there when it wasn't flowing......just another suggestion.