Merc 350 Horizon Fuel Pumps

bnc · Postby **bnc** » Tue Jul 05, 2022 8:55 pm

Any one had a fuel pump go out on one of these engines?

Had an engine stall and not want to restart this past weekend. Suspected fuel issue as I had just changed the fuel / water separator filters. Fuel pump sounds weak compared to the other engine. Gauge shows low pressure on initial key-on, but will get to 40psi on attempt #2 or #3. Didn't attempt to start it with the gauge attached.

Haven't had a chance to take it apart, but I suspect the low pressure pump failed.

Quicksilver brand pumps are about $700 for both high/low pair. They are also mostly out of stock every where too.

Lots of cheap china pumps on eBay, but no thanks.

I bought the QS pumps, but also bought a Walbro low pressure pump to compare off eBay. Less than half the cost of the Merc. Internet says the Merc pump is a Walbro. No cross that I can find for the high pressure one.

866169T01 High Pressure
866170A01 Low pressure

Woodworker2001 · Postby **Woodworker2001** » Fri Jul 08, 2022 6:58 am

I have not had one go bad. I did have some injectors go bad. I know that there is nothing fun about changing the port fuel pump as it is on the outside of the engine. Best to get yourself midget gymnast with 7’ arms.

Did you prime the water separating filter with fuel when you replaced it. Mine doesn’t like to pickup fuel without filling the filter.

Let us know how you make out

bnc · Postby **bnc** » Thu Jul 14, 2022 5:57 am

My engines have the Cool Fuel Gen 3 modules. They are mounted on the starboard side of the engines and of course the starboard pump failed.

Changed pumps with Merc parts. Pump is noticeably quieter than the other now. Problem solved. Broke 3 or 6 bolts off and had to drill them out and helicoil to fix. Hits 43psi at first prime, then holds ~38 psi idling. Same as the other side.

I did not prime the filters originally. I did prime them while attempting to fix the problem, but it was too late.

Woodworker2001 · Postby **Woodworker2001** » Thu Jul 14, 2022 8:01 pm

I bet that was a hell of a job. How did you manage to drill bolts and helicoil them clear on that side of the engine? Or were they bolts that were on the pump in your hand?

bnc · Postby **bnc** » Fri Jul 15, 2022 5:33 am

Woodworker2001 wrote:Source of the post I bet that was a hell of a job. How did you manage to drill bolts and helicoil them clear on that side of the engine? Or were they bolts that were on the pump in your hand?

The fuel pump module was out of the boat at the time.

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