Vacuum fuel pump

Discussion in 'DIY Marinizing' started by Rangerspeedboat, Apr 19, 2009.

  1. Rangerspeedboat
    Joined: Apr 2009
    Posts: 120
    Likes: 3, Points: 0, Legacy Rep: 17
    Location: Texas

    Rangerspeedboat Senior Member

    I have heard that you cant use a gravity fed engine as an inboard. I wondered why at first then realized that the line may leak causing fire or something.

    I have seen these vacuum fuel pumps used on briggs motors that operate by the crankcase vent,

    Here are instructions for installing a fuel pump on gravity fed engines
    http://www.affordablegokarts.com/fuel-pump-setup.php
    In the instructionshe says nothing about the existing crankcase vent. I dont know if the new engines have one or not.

    I want to install one on on an engine like this

    [​IMG] Not my pic

    These engines have have the crankcase vent where the springs are which goes to the carburator.
    If I used one of those fuel pumps how would it work?
    Would I have to plug the existing crank case vent?

    I am going to install a fuel pump on the engine but I want to learn about it first.

    Thanks, Ranger
     
  2. Rangerspeedboat
    Joined: Apr 2009
    Posts: 120
    Likes: 3, Points: 0, Legacy Rep: 17
    Location: Texas

    Rangerspeedboat Senior Member

    Here is the valve cover vent leading to the carb

    [​IMG]
     
  3. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 476, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    That's an "L" head engine and the vent isn't actually necessary for the carb, but emission laws forced them to do it this way.

    The vent can be relocated to the air cleaner or any place in the incoming air charge going through the carb. If in the air cleaner, use a small foam filter so you don't oil soak the air filter element.

    Of course you'll need to plug the big hole in the side of the carb.

    Instead of rigging up a Mickey Mouse garden tractor fuel pump, use a real, low pressure fuel pump and cheapo regulator. You can get a electromagnetic pump for about 20 bucks and a regulator for around 15. The pump is only good to about 5 PSI, but this might overwhelm the needle in your carb, so use a regulator to crank it down to a point it doesn't flood. The pump will pressurize to 5 PSI and shut itself off, the regulator will feed the needle what it wants and when the pressure drops enough, the pump will turn itself back on.

    There are a lot of hot rod tricks you can do to that engine to get more power out of it. Just rejetting the carb will yield a couple of extra HP. Learn how these engines work and you can make them scream, like what to do with the governor arm.
     
  4. Rangerspeedboat
    Joined: Apr 2009
    Posts: 120
    Likes: 3, Points: 0, Legacy Rep: 17
    Location: Texas

    Rangerspeedboat Senior Member

    So I dont need the vent there, I kind of figured that but I had to make sure. I had an old briggs 2hp that didnt have the vent there, it just had a tube blowing the air out.

    I like the electric fuel pump idea, but I think I will stick with the vacuum pump. Its simple, and requires no battery or any other expensive stuff.
     
  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 476, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The engine you have generates power, which will charge a starting battery. As long as your stator is working, your battery is good and have no wiring issues, it's self contained.

    You still need the vent routed to the intake air flow (before the throttle butterfly). I don't know how many partially spent petrol molecules can escape, but if enough do and a spark exists, then a loud boom will result. With the hose just dumping into the bilge, you quickly have oil all over everything anyway.
     

  6. Rangerspeedboat
    Joined: Apr 2009
    Posts: 120
    Likes: 3, Points: 0, Legacy Rep: 17
    Location: Texas

    Rangerspeedboat Senior Member

    Well the pump works, I connected it up a few days ago. Go to tiny power boat in boat design for pictures of the pump
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.