1956 30 hp Big Twin. Want to convert to single gas line, need advice.

[subnrc]

I have a 1956 30 hp Big Twin that is in really great shape. The engine runs like a top if I keep pressing the tank's manual pressure plunger.

I understand that there are numerous reasons that a pressurized fuel system like this one can be problematic and even dangerous. I've replaced the fuel lines and checked the tanks for leaks, everything looks fine. I'd like to convert to a single line system with a fuel pump. What is the best route to take?

The boat has two pressurized gas tanks that are also in great shape. I'd like to use these tanks if possible. Can the line that used to provide pressure to the tank be safely used as a vent?

Thank you in advance,
subnrc

 

[JB]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

http://forums.iboats.com/showthread.php?t=380378 From the Top Secret File ^^^.

 

[subnrc]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

JB,

I am sure that my system is a two-line pressurized system. The questions I am looking for help with include just how to go about converting my 1956 30 hp Big Twin from a two-line pressurized system to one with a fuel pump, and whether or not I can adapt the two pressurized system gas tanks I have to work with the new fuel pump system and how to go about doing it.

Any and all suggestions are greatly appreciated.

Thank you, subnrc

 

[kfa4303]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

Hi subnrc. These should help. Beware, NOS and OEM pumps can be a little pricey (aprox. $80-$100), but lots of folks use brands such as Mikuni and Briggs & Stratton with great success as well. Holler if you get stuck.

http://www.leeroysramblings.com/Converting_dual_fuel_line.htm

http://www.youtube.com/watch?v=FtG4M7ye1N8&feature=related

http://www.aircraftspruce.com/catalog/eppages/mikunifuelpump1.php

http://www.marineengine.com/parts/v...ntage-evinrude-johnson/376750/37675000001.htm

http://www.duckworksmagazine.com/04/s/columns/max/24/index.cfm

 

[HighTrim]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

You can easily convert to a single line setup. You cannot use your current tanks, nor can you use your current fuel barb on the motor, you will need to get a single line connector. Your best/easiest method would be to find a bypass cover/pump from a newer Big Twin, then it would be as easy as swapping bypass covers, plugging the old pressure line with a bolt, swapping connectors and changing/rerouting fuel line.

By the way, regardless of what you read, a pressure set up is neither dangerous nor problematic in my humble opinion. I have never, ever heard of one exploding like some online articles will make you believe.

The primer button simply feeds fuel to the fuel bowl, it does not pressurize the tank. The motor does that. You have a leak somewhere, not allowing the motor to pressurize the tank, feeding fuel to the carb while running. A rebuild of the tank will cure this. That is not to say that swapping to a fuel pump is a bad idea, I have done many of my motors myself, just letting you know another option to fix your current issue.

 

[subnrc]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

Thanks for the replies gentlemen,

I've found that my tank still has loads of pressure even when the engine was cutting out by slowly unscrewing the tank's cap and releasing the pressure.

I'm going to head out tomorrow to find the parts I need to make the conversion. I'm figuring that I can recoup some, if not all of the expense of converting by eventually putting my old tanks, hoses, and couplers up for sale.

This engine does not appear to have the right side plates with sufficient bosses for drilling and tapping as suggested by other posts to mount a stock pump.

There is a boss on each plate that would allow the drilling and tapping of the 1/8" NPT and attaching a nipple, so I'm planning to adapt a remote pump such as the Mikuni 07-00777 pump.

I'll let you know how I make out.

Thanks again for all your help,
subnrc

 

[HighTrim]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

No, as stated, if you want to mount a stock pump, you need to replace the bypass covers, or make an adaptor plate.

You can always run a Mikuni as well by simply drilling and tapping in a fuel barb.

 

[F_R]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

If it won't run with pressure in the tanks, it probably won't run with a fuel pump either. Just sayin.....

 

[subnrc]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

I realize that there may be other issues that are keeping her from running well but I'm hoping to alleviate some of the problems by taking this step.

I've taken out the nipple that use to feed pressure to the tank. Does anyone know what thread this is. It does not appear to be tapered like a pipe thread, nor does it appear to match up with any small diameter SAE threads. Is it possible that this is a metric fitting?

subnrc

 

[HighTrim]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

Make it easy. Just leave a piece of fuel line on it a few inches long, then plug it with a bolt and clamp. Makes it easy to swap back over if you ever sell it. Taking out the nipple will only lose it.

 

[subnrc]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

Chris,

Thank you, that is good advice. I wasn't sure how much pressure there was at this port but this method seems more than sufficient.

I removed the upper bypass cover thinking that the inside surface would be flat. Instead it is curved and the end where I will be drilling and tapping is fairly thick. Is a drilled hole in this location likely to create problems?

Thanks again, subnrc

 

[HighTrim]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

I have plugged dozens of the nipples with bolts of a suitable size, never an issue. Just put a hose clamp on the hose/bolt.

Drill tap right in the center of the bypass cover. Looks thin but there is sufficient material.

Here is one I just did.

 

[subnrc]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

Its all back together with a clean carburetor, new needle and seat, new packings. I've left the pressurized system intact. I'm going to give it another try with the old system.

When everything was all back together I gave the tank's primer pump a bunch of pumps hoping to see if the needle valve would close against the seat (I tried it with air pressure before putting the carburetor back on and it seemed fine). Gas ran out of the carburetor eventually telling me that the float was not closing the needle valve. I took it all back apart and adjusted the float, then air tested it again. Everything looks great.

1. Is it possible that the primer pump could provide enough pressure to force gas past the needle and seat?

2. Can the air filter fabric be cleaned? Does anyone still carry these air filters? It looks like a neatly cut piece of fiberglass insulation, with no loose fibers.

As always; Thanks for your help,
subnrc

 

[subnrc]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

She runs! Had her running in barrel this afternoon. Going out on the lake later to give her a good run and jet tuning. She did cough a bunch of black crap out that had me worried. I talked to a helpful friend at a local marina about it. He figures that it was old oil that had accumulated in the lower cylinder. I was afraid the lower unit seals were toast. I'll let you know how things go.

Thanks to everyone for your help!

subnrc

 

[subnrc]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

She idled fine. For about 30 seconds at a time it would go full throttle. High and low valves when set at 1 1/4 turns allows a nice idle. I had my wife drive while I slowly adjusted the valves to get her to run at full throttle. Each time it ran good at full throttle it would then cut out after about 30 seconds. Do I need to do something like adjust the float to allow more gas in the bowl?

Another issue arose while we were out. I believe it has something to do with the neutral safety switch. No matter what position we put the shifter in the starter would not work. At home I tested the starter terminal to see if it was getting voltage. It is not. Where and what do I look for?

Thank you,
subnrc

 

[HighTrim]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

It does sound like you are running out of fuel. Start with the high speed needle out 3/4 turn from lightly seated. Ensure the float is dropping and not sticking. Did you install a new needle/seat with the wire clip? This ensures the needle does not stick in the seat. The new needles also have rubber tips. How is the float drop?

Is the mercury switch parallel? If you ground the lead that runs to the mercury switch does she fire?

Im assuming the battery is fully charged and load tested, connections clean/filed and tight. No wiring corrosion. Are you getting voltage at the solenoid, and on the other end of the solenoid when the starter button is pushed?

 

[F_R]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

About that air filter. It is not an air filter. It is a silencer. It doesn't even need that packing in there. Maybe you will notice the extra noise without it, maybe you won't --or won't mind.

 

[1946Zephyr]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

Make sure your 0-rings in your fuel line connectors are good. If any of them are leaking, that could be part of your problem. Fixing what you have will be much cheaper than converting. If your tank is building pressure, then that is a great sign. The problem sounds like it's at the carb. How does your ignition look? Often times, ignition problems can lead us to believe the carb is the problem.

 

[subnrc]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

Last week I took the boat and motor to a nearby marina to have an experienced mechanic take a good look at the motor and make the necessary repairs. They rebuilt the carburetor. They found that the solenoid was shot. They also discovered that it had lost spark. I asked them to remove the flywheel and expose the ignition to see if it needed anything. I plan to replace the points and coil.

They found that the upper seal was bad and gave me a call suggesting that they would have to put significant extra time in fixing everything. I asked them to go ahead and order the solenoid and the upper seal. The mechanic was concerned about the lower seal as well and said that replacing the lower seal would require removing the powerhead. I plan to bring the boat and motor home this afternoon and make the remaining repairs myself. Should I plan on replacing the lower seal also.

I am going to need some coaching as to the steps needed for replacing both the upper and lower seals.

Thank you, subnrc

 

[HighTrim]

Re: 1956 30 hp Big Twin. Want to convert to single gas line, need advice.

What made him mention the lower seal other than added money?