I was having some fuel issues this summer on my carb 383 Chevy. Every once in a while it would stumble and my AFR would go lean. When this happened my normally cold fuel bowl would be hot, so would my lines and pump.


I have more pump than I need. It's a Holley Marine Blue pump running into a deadheaded regulator and a carb. I opened the pump up and it's still nice inside.

When the engine stumbles my fuel pressure gauge bounces and goes under 3 psi. When It comes back to the 6.5 psi set point everything gets happy again.


I replumbed my fuel system to Holley's recommended 3/8"ID. The Mercruiser fuel system that my 350 Mag came with is 3/8"OD. I missed that ID issue on the original 383 installation. I also added a bypass for cooling.

There's 3/8" ID marine rubber line to a 100 micron filter between the tank and the pump. I did new copper from the pump to the fuel water separator. I tapped out the separator housing to 3/8" from the OE 1/4". and I ran the copper to a bypass regulator, where it returns to the tank and goes to the motor.


I was just about to start my engine when it hit me. Mercruiser puts the fuel water separator in the suction side of the fuel system. Can any of you think of any reason I can't leave it on the 14 psi delivery side of my electric pump?

Yes pump not protected from sucking junk in.

What he said ^^^.

It’s better than nothing, but the fuel pump can be very sensitive to dirt.

On a side note, I installed my fuel filter/separator higher than the pump so it always has a bit of head to start on.

Water/separator filter works fine under pressure. It won’t protect your pump from any water, if your worried about that.

I have two boats running this way for 15 yrs or so. One mechanical pump and one boat electrical. Yeh, inline 100 micron before electric pump. None before the mechanical one.

Why fdid I do this ? Just because. Lol. Work fine and seperstors still catch water if present.

I once had some tiny shards of teflon tape get stuck in the mechanical pump check valves (from prev owner repairs). The pump could only produce abt 3 psi of fuel press at times, other times it was around 7 psi. Almost burned up an eng over some debris so small I could barely see it. I'd have to recommend some kind of filter before the mechanical pump.

Yes, maybe I didn't say it well, but I did a prefilter with Holley's recommended 100 micron rating.
So today if it passes a leak check I will get one more ride before winterizing.

Supposed to be near 70, one last time today. Good for you. Jealous !

If you haven’t been on the lake for several weeks, Lake is way down. I spent last week-end pulling rocks near my dock I haven’t had to worry about, othen than one other year 4yrs ago ? In my docks 45yr old lifespan. Doh !

Yes, it's the lowest I recall and I've been boating here since the early 70's.
Regarding rocks. I won't say what lake this is on...
My buddy rents his 80 year old waterfront camp to one of our engineer friends. Mr. Engineer realized about 20 years ago that he could put slings under the PITA rock in front of buddy's dock. Hooked up a big air bag and floated it out deeper! Some times it's the simple things.