TOPIC: Evinrude 1956, 30hp, lark

Good evening,

I’m searching for detailed information on converting my dual fuel line to a single line.
Can anyone point me in correct direction?

Hi, you have to have a source of crankcase vacuum/pressure to make the fuel pump operational.

Best place for that is from the intake port cover, which is how later model Big Twins with fuel pumps were set up. See attached pic of the intake side of the block. You'll note the (2) intake port covers, each has a hole in it.

I don't think your 30hp has the same size port covers as later-model 35hp and 40hp models, otherwise you could pull parts off of one of those and use a port-mounted fuel pump. 30 hp is an oddball as it's a transitional year; in '57 they came out with the BigTwin 35, and I'm thinking the '56 30hp was a derivative of the older 25hp Big Twin. If you had a later-model 35 or 40-hp cover to compare, it'd be easy to figure that out. Or maybe one of the OMC Guru's here remembers.

IIRC you can tap out that hole to 3/8"-NPT and use a 3/8" 90-degree brass nipple. You have to drill-open the hole all the way thru the intake port, in order to see crankcase pressure pulses. Remove the cover before drilling, or you'll get a bunch of nasty shavings inside the crankcase.

On later Big Twins, the intake port cover was a bit different and had enough casting for 2 smaller mounting holes, which mounted the fuel pump against the cover with a gasket and 2 screws. You won't be able to do this with your existing port cover. So you'll have to figure out some sort of mounting bracket for an aftermarket fuel pump. You need the type of fuel pump that uses a hose to the crankcase, not the type I just described that mounts directly to the cover. Many fuel pumps, of different brands even, would work. There's an abundance of new and used pumps on eBay that could be made to work.

Here's an inexpensive pump: https://www. ebay .com/itm/362664577101 Note the (3) connections, (2) for fuel and (1) to the crankcase (transfer port cover).

This site still parses ebay links, so you'll have to copy the link, paste into your browser, and then remove the spaces.

You'll also need a single-line motor-side fuel connector, something like this:

https://www. ebay .com/itm/384314201269

You'll need to plug-off the air fitting that pressurizes the remote fuel tank. This can be done as easily as a machine screw with a washer. You'll need to tap the small barb to accept a short screw with a fiber sealing washer.. Or you can leave a length of line attached to the air fitting barb, and plug the end with a screw and clamp. Crude but effective!

There are a number of other ways including silver-soldering closed the hole in the barb. Or pulling the carb, disassembling intake manifold cover and reed plate, and plugging the 2 holes in the plate. More complicated and for the latter, you'll likely tear a gasket and they can be hard to find. Personally I'd just keep it simple.

Last things I didn't cover, you will of course need a new single-line fuel tank and the appropriate OMC single-line fuel connector. You can probably pick one of those up at your local Walmart, and check Craigslist for good used tanks. Any tank can be used as long as you can put the J/E fitting on the end.

Also, you'll have to decide for yourself which intake port cover to drill and tap; top of bottom. It won't make any diff to the fuel pump, just how much room you have in there to run the fitting, hoses, and mount the pump.

HTH..........ed