Electric fuel pump instead of primer bulb on outboard

[dorsett59]

Just running this up the flagpole to see what happens.
I had the thought of using a low pressure (2psi) electric fuel pump in place of the primer bulb on an outboard. I have a long-ish fuel line (5 ft) from the fuel tank to the engine. There's not a lot of elevation change, but the engine starts VERY hard unless I'm pumping the bulb 20-30 times. Yes, I've already replaced the bulb, and had no improvements.
Or is this just a Bad Idea?

 

[Chinewalker]

Re: Electric fuel pump instead of primer bulb on outboard

Why not fix what's wrong? The motor really ought to start with just a couple pumps on the bulb, particularly if it's been run relatively recently. Your issue sounds more like a starting procedure issue, or possibly a faulty choke/enrichener on the motor...

 

[dorsett59]

Re: Electric fuel pump instead of primer bulb on outboard

The engine runs fine once it's started.
Already replaced all the lines between the fuel tank and the carb, installed new connectors from the fuel tanks to the engine quick disconnect. Engine starts in 1/2 crank when warm, have installed electric choke that does everything the manual choke does. And, as I said, I've replaced the primer bulb a couple times.
The issue seems to be fuel not getting to the carb after it's been sitting for anything over 30 minutes.

 

[CharlieB]

Re: Electric fuel pump instead of primer bulb on outboard

Temporarily install a clear hose between the fuel pump and carb(s) watch while running for any air bubbles passing thru indicating air sucking into the system before the fuel pump.

Leave it sit overnight and see if the fuel lowers in the clear hose, possibly indicating leaking check valves in the fuel pump, primer bulb, fuel tank check valve, allowing fuel to return to tank.

Concerns of low fuel flow on a long hose can be eased by increasing hose diameter.

Problems with aftermarket fittings and primer bulbs have caused many to only use factory fuel fittings, much better quality than a lot of the imported stuff.

 

[Silvertip]

Re: Electric fuel pump instead of primer bulb on outboard

You and about a hundred other folks have asked the same question and the result is always the same. Don't do it for safety reasons. Electric fuel pumps are used on modern EFI/DFI engines because of the higher pressures needed. For safety reasons, the engine management system shuts off the pump automatically if a malfunction occurs (engine stalls and the key is left on for example). Without this feature, an engine can be literally pumped full of fuel. An attempt to start it may result in exposion and fire. Your engine has no such capability. Besides -- pressurizing the fuel line constantly means any leak between the pump and the engne means fuel can be sprayed everywhere. There is absolutely no reason to inistall an electric pump on a carbed outboard and no simple way to trigger a safety circuit. Can it be done? Certainly! How electrically savy are you?

 

[boobie]

Re: Electric fuel pump instead of primer bulb on outboard

The old OMC V-8,s had an electric primer pump on them that was only activated when you pushed a button and still let fuel flow through it when running. Maybe you could find one of them.

 

[Faztbullet]

Re: Electric fuel pump instead of primer bulb on outboard

Yep it was a electric primer, part number 174651. You can use the fuel pump as a primer if you plumb it correctly as this will need a check valve as this keeps fuel from being drawn thru pump by engine.It will also need to be fused.

 

[sschefer]

Re: Electric fuel pump instead of primer bulb on outboard

Merc say's you can run a 2lb pusher style pump from the tank to the engine and eliminate the bulb. However, you can only do that with an above deck tank because the pump has to be level or below the bottom of the tank for it to work correctly. With a built in tank that would put the pump in the bilge and the USCG frowns on that. All below deck tanks have the outlets on the top and should have anti-siphon check valves (except diesel) so that they do not drain into the bilge. The alternative is to run a 2lb pusher pump into an above deck surge tank and then push fuel from it to the engine and remove the engines puller style fuel pump. That works excellent and is safe but the cost is a lot more and it's rarely seen or needed in a recreational application.

The problem you have could be as simple as a bad anti-siphon valve at the tank. Fixing that is a lot cheaper then electric fuel pumps.

 

[Faztbullet]

Re: Electric fuel pump instead of primer bulb on outboard

As long as pump is BIA/NMMA certified like a Walbro or Carter you will not have a problem.....

 

[j_martin]

Re: Electric fuel pump instead of primer bulb on outboard

I agree with sscheffer.

If things are as they should be, a quick squeeze of the primer bulb just before launch sets it up for a normal day. It might take 2 or 3 squeezes for the first time in the spring. It also gives you a chance for a quick fuel system integrity inspection. If it pees gas on your boots, don't launch the boat.

After that, you should not have to touch the primer bulb for the rest of the day.

What can go wrong.
2 check valves in the fuel pump
2 check valves in the primer bulb
anti-siphon valve in fuel tank
pickup tube in the fuel tank.
All the clamps and fittings between the engine and the fuel tank.

None of the above is hard to diagnose and fix, and any fix including replacing everything is going to be both less expensive and less dangerous than an electric priming setup.

hope it helps
John