455 Oldsmobile Big Block w/ jet drive

[turner24]

Hello all,

I have a stupid question about my 455 Olds fuel pump. This boat was purchase 2 years ago and I'm finally starting to restore the boat. The motor was rebuild along with a new carburetor. The only way I can get it started is by plugging what I think is suppose to be the return line that should go back to the fuel tank? If I don't plug this line gas pours everywhere. Here's a pic:



I have no idea where to route this line. I was told by a buddy that it's probably a return line to the gas tank. Here's more pics:



Please help! Thanks..

 

[Don S]

Re: 455 Oldsmobile Big Block w/ jet drive

You need to find the proper "Marine" fuel pump. That is probably automotive, and not designed for marine use.

 

[turner24]

Re: 455 Oldsmobile Big Block w/ jet drive

I was actually thinking the same thing. If anybody knows where I can get one online please share the link. Thanks!

 

[turner24]

Re: 455 Oldsmobile Big Block w/ jet drive

I believe this motor is a 1968 but I am not 100% sure. Does anyone know what year this motor is and where a good place to get parts?

 

[RogersJetboat454]

Re: 455 Oldsmobile Big Block w/ jet drive

I was actually thinking the same thing. If anybody knows where I can get one online please share the link. Thanks!

I think you may be bumming...
If you can't find one, you will need to make/buy a block off plate for the pump boss and get a marine grade electric pump. If you do go electric, consider wiring it so that an oil pressure switch controls power to the pump.

 

[turner24]

Re: 455 Oldsmobile Big Block w/ jet drive

Hopefully I can find one. What's the advantages of going electric?

 

[turner24]

Re: 455 Oldsmobile Big Block w/ jet drive

If I can't find one I was thinking about just blocking off the extra line. Do you see a problem in doing so?

 

[Luhrs28]

Re: 455 Oldsmobile Big Block w/ jet drive

I agree with RogersJetboat: go electric. One advantage is you can locate it almost anywhere. Plus it's marine-rated.

I don't think you can just block off the extra line on your existing pump. At idle the fuel float in your carb has the inlet valve just about totally closed, which means the fuel pump has to return 99% of the fuel to the tank. (if it were in a car) If you plug off that return fitting the pump could build up enough internal pressure to rupture the rubber diaphragm inside.

 

[RogersJetboat454]

Re: 455 Oldsmobile Big Block w/ jet drive

Hopefully I can find one. What's the advantages of going electric?

In your case.... replacing a mechanical fuel pump that's made out of unobtanium...

 

[RogersJetboat454]

Re: 455 Oldsmobile Big Block w/ jet drive

I don't think you can just block off the extra line on your existing pump. At idle the fuel float in your carb has the inlet valve just about totally closed, which means the fuel pump has to return 99% of the fuel to the tank. (if it were in a car) If you plug off that return fitting the pump could build up enough internal pressure to rupture the rubber diaphragm inside.

This...
Plus, if this is a closed bilge boat, and the pump does let go, you risk filling the bilge with fuel and fuel vapor. If who ever put this together used an automotive starter, alternator, distributor (any or all of them), you will set your self up to be a crispy critter. Probably should be mentioned that if the builder was careless enough to use an automotive fuel pump, you should be checking all all the above mentioned to be sure they are marine grade, along with the carburetor.

 

[Don S]

Re: 455 Oldsmobile Big Block w/ jet drive

Get a marine rated fuel pump, and hook it up to an oil pressure switch so it doesn't run with the key on and the engine off.
Mercruiser gets power from the starter solenoid to run the pump while the engine is just cranking.
Here is how Mercruiser wires in the fuel pump.

 

[turner24]

Re: 455 Oldsmobile Big Block w/ jet drive

Any recommendations on what brand/model to buy? Thanks Guys!

 

[turner24]

Re: 455 Oldsmobile Big Block w/ jet drive

If I go ahead and put in an electric fuel pump, what should I do with the mechanical pump?

 

[RogersJetboat454]

Re: 455 Oldsmobile Big Block w/ jet drive

If I go ahead and put in an electric fuel pump, what should I do with the mechanical pump?

Option 1. Chuck it.

Option 2. Put it on a shelf, and keep it just in case you happen to encounter an Oldsmobile with a return style fuel system that needs a pump.

Option 3. Sell it as a used fuel pump to someone who doesn't mind buying a used fuel pump.

Option 4. Have it gold plated, and make it into a trophy, wall hanging, or lamp.

 

[Don S]

Re: 455 Oldsmobile Big Block w/ jet drive

Here is a pump used quite often when converting from mechanical to electric. http://www.iboats.com/Electric-Fuel...7272094--session_id.458658337--view_id.203982

An auto parts store will probably carry the oil pressure switch. You need a normally open switch with around a 5 to 7 psi closing range.