Blower fuel pump dilemma..
 

Last winter I re-did my fuel system to run twin-750 carbs on my blowers. I run 1/2" fuel line out of the tanks, through a hi-flo filter, and into a Holley marine Mechanical pump (130gph) mounted on my water pump. The "arm" of the pump was modified to run on the water pump. The Holley pump is 1/2" in and 1/2" out. On the "out" side I have a boss that lets me connect my -6 fuel lines and fuel pressure gauge.

One of my pumps went out this past weekend. The seal around the arm came detached and it started dumping fuel into my the reservoir that holds the gear lube. I ordered another Holley pump, but found out they are changing to 3/8" in/out due to the same seal failure I had. The pump is still rated at 130gph. If I adapt my fittings down from 1/2" to 3/8" on both sides of the pump, will I still be getting enough fuel to my carbs? I still have my old pumps which had 3/8" fittings and were modified with Carter hi-flow pumps so I could also use them I guess...

Thanks in advance..

BTW - I spoke to Holley tech support. He confirmed that the Marine 130gph mechanical pump is going to 3/8". He also said it would be plenty to feed my twin 750s.:confused: :confused:

I have a non marine pump that has 1/2" ports. I believe there is a boss for the drain hose that would be needed. $30 Any interest?

Wow, this thread is going no where. Nobody has an opinion?

Here's an update from my end. Nobody has any of the old 1/2" Holley pumps in stock. I sold one about a year ago, and the person I sold it to is being kind enough to sell it back to me (Thanks, John, very nice of you). So, I will have 8 fuel pumps in my garage trying to get one to work:

(1) Holley 712-454-1 with the pump arm modified, but the seal is screwed;
(1) Stock Merc pump;
(1) Stock Merc pump lower with the Carter HV upper (1/4" I/O)
(2) Carter HV pumps (model M4889) 1/4" I/O
(2) New Holley 712-454-13 pumps are being delivered Thursday from Summit. According to their manuals, they replace the 712-454-1 pumps, but have the 3/8" I/O.
(1) 712-454-1 pump with the stock arm.

I also went to NAPA and bought a 3/8"NPT and a 1/2"NPT die so I can tap out anything I end up with. In order to get running for the weekend, I'm thinking I'll take one of the Carter HV pumps, tap it to 3/8", adapt it to 1/2", and try that. Or, I can take one of the Holley uppers and bolt it (with some machining) to a stock Merc lower (I found out there are two other "blown" boats in Richmond that have done this). Somehow, I'll be riding this weekend, even if I have to spit fuel into the carbs with a straw.

Cignificant,
I'm sure someone should know the answers to your questions. Call Bruce Wolff, his shop builds a lot of blower engines for marine use and he has always told me that "there is power in a fuel system". He might be a good one to call 616-422-1090. 8-5 EST.
Also, "Doctor Dave" (OSO board member) might be able to help answer your question. 616-944-0214 after 6pm EST.

CIG, I have a brand new Holley 130 gpm 1/2" marine pump I will sell you for what I have in it. I have to look. I think it was around $50 or so. Email me with your email or phone number.

I have another 1/2" pump coming in from another source. Here's my status: I recieved the new 712-454-13 pumps. They look exactly like the Carters, except they are 3/8", have the tube, and shine. I installed one of them, reducing my 1/2' lines down to the 3/8". Cranked up the engine - I get a solid 8# of fuel pressure. I only got 5# with the 1/2" Holley pumps - go figure!!

Cig, you are going to show more pressure if you decrease the size of the hose and fittings but you wil have less flow (GPH).

I agree, less pressure but more volume with the 1/2" feul lines.

Mmm - that doesn't make any sense to my simple mind. My fuel pressure sensor is mounted on the end of the fuel block coming out of the pump. This same block is used to attach the dual -6 lines running to the two carbs. So what it is measuring is the pressure in the fuel block afer the 3/8" restriction. If the pressure is higher, it means more fuel is entering the fuel block.