Hardin on line tech support suggested a different non foaming lube, lower lube level and run the vent kit. Fluid does return to the pump. They also stated the just used Merc design with "better" parts. I am sure it is not water in there. New pump should have cured the possibility of fuel in the oil. I will say this, this pump is running much hotter than the port engine pump.

I would say Hardin is giving you a circumvention to the problem not a fix. To suggest you need to treat one different than the other makes no sense. Both pumps should perform the same with the same oil at the same level.

I would ask them why one runs at a much higher temperature that the other.

How old is this pump?

I don't think they have a solution except the vent tube. Their exact reply is pasted below.

"I don't believe I will provide a solution to what I believe is a poor OEM design.This is 100% a Mercury design that we have duplicated with better quality materials. You could of course discuss the design with Mercury? Their number is 920-929-5040
Because the pump has a cam lobe that drives the fuel pump it creates "Windage" in the same manner a crankshaft does. The l;argest culprit to extreme failure has always been leaking fuel pumps because they then create "Vapor". The pressure created has to find a path somewhere and inherently has been known to push out seals. We even glue seals in during assembly today to prevent from this.
Some options may be to reduce the oil level slightly?
or try an Anti-foaming oil?
Or go away from that style fuel pump and block off that chamber of the pump.

As you already realize we came up with a vent system; it's inherently a bandaid to a design that is flawed. Many people extend the vent line length allowing the pump to sort of burp out and the oil travel back down into the pump."

I would consider a known good used Merc pump to get through the Summer if anyone want to help a guy out. I'm going to hit up a couple places here at LOTO for a pump early next week. Have to finish a house plumbing job today and other backlog crap.

I don't disagree with anything Hardin says. It is improved over merc to address a common problem when fuel pumps go south.

But, you have a pump that is performing differently than the other. The fact it is generating more heat is symptomatic of a problem either with the cam driven fuel pump or the front/rear bearings. Everything else is inert.

Have you vented the other reservoir and is there any trace of oil in the vent line.

No to the last question. The other pump is a Merc with a Hardin impeller housing. It was serviced with fresh lube and new impeller before the season.

I guess you can't compare apples to apples. I am not buying the windage comment given the cam lobe characteristics.

So are you going to run as is or get a new pump.

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Helmwurst,

My brand new Hardin Pumps did. the same thing. I plan to add a "vent tube" to alleviate the pressure.

Some progress yesterday. Pulled the fill plug to suck out the drive oil in the pump. Oil came out because there was too much in there as the motor sits in the boat, oil looked clean and did not smell of fuel. Put the plug back in after it quit dripping out and ran up the Lake to a dock party. Inspected the vent tube and it had only risen up about and inch and went back down after a couple minutes. Next test is to go ahead and replace the oil and fill just to the bottom of the fill hole per the instructions from Hardin. Will make a decision on a different pump after that.

Doesn't matter what pump you get, they're all eventually going to leak fuel. Airtex as been suggested here on the forum. I bought 2 and just replaced one this week due to fuel leakage. The OE Merc. did the same. Just bought another $60 Non-Airtex pump as they got more expensive. Like I said all are going to leak at some point anyway. Additionally, I use non-ethanol fuel and found most pumps state "not for use with fuels containing alcohol (ie ethanol). I assume if using fuel with ethanol it's going to eat up the pump seal even faster.
I have a compete aftermarket billet sea pump sourced from ebay that at least uses sealed bearings so the only portion being lubricated is the shaft lobe and fuel pump armature.

What fluid do they specifically suggest? I use Merc. 90 Wt. drive lube which is billed as "non-foaming".