1995 GT-40 Fuel Pump/FCC conversion

Thanks for the picture Trevor

Another thought, any chance these boats lost an impeller prior to this issue?
If impeller chunks are blocking some of your exhaust coolant on that side it may be exposing your pump to more heat than normal?
Just a thought.

The design of the low pressure pump gives it plenty of power to pull the fuel from the tank to your engine mount and then to supply the High Pressure Pump. You can move it to the tank area if you wish but I think that risks putting it under water if your bilge fills and that would be bad and could happen any time in a boat.
We need to think more about what PCM thought when they installed the second line in that pump. I can't think of a reason for it to exist? No automotive applications use that system so it must be something they think is important to a marine application.
Does it feed the Fuel Rail before or after the pressure regulator?

    OK, I took my cover off and got pictures of my 95. I also looked at the Fuel system.
I don't like it at all.
The return line that should feed to the fuel tank does not. The return line dumps into the second port on the High Pressure Pump.   If it could be modified to dump the return into the tank the system would run cooler by far.   I could see this design having failure issues.
There has to be a valve in the current HPP to receive the return fuel from the pressure regulator and not let pressure from the pump shoot back at the pressure regulator.
Silly system. PCM should have got some advice prior to doing this in my opinion. Which is not worth much. If your HPP is bad it would be possible to build a T out of brass couplings that bolt together and use the new Fuel Pump like the one available at JEGS in the pictures and plumb the return line direct into the fuel supply line and then into the High Pressure pump. It would function the same as the factory Nautique system.   If it lasts 10 years that would be great and easier than routing a new return line to the tank directly. A couple photo's of mine and the newly installed Timmy T. Thanks for that Tim. Mine is 1' not 3/4 in the 95.

Paul, doing it the way you plan will make the fuel pump dead head. Your fuel pressure will jump to the max the pump can attain. Might be 50+.
You have to have a return line.   Maybe yours has a second line to the tank. I did not find one on mine. It would be pretty obvious.   I think they knew a return was needed and thought what the heck, put it back in the line feeding the HPP. Sounds good until something gets hot.

Looking at the fittings used they are good quality but they were purchased from a speed shop type supplier not from an high volume OEM type supplier. They would all be the same color. Gold. The reds and blue fittings are common aftermarket fitting where Bling is needed.

I put my head down and looked yesterday and did not see a return fuel hose, only the feed hose was visible. On the driver side I only saw the steering cable. If the return line is there that is good and it should be there.

Maybe some member here can comment on the need for the second line feeding the fuel pump.
The new fuels available with a grain mix are much more prone to have fuel vapor lock issues. than petroleum based gasoline.

The Fuel rail pressure regulator receives fuel at whatever the pump puts out, could be 47 to 60 PSI, it bleeds off pressure to keep the constant 39 required in this engine. The constant Fuel Pressure lets them predict how much each injector will spray and they tune from that. If fuel pressure drops the injectors won't spray right and if pressure goes up you feed more fuel than planned.
The excess fuel bled off goes to the tank and the extra flow keeps the fuel rail cool and helps avoid any hot fuel issues. When I get time I will trace my fuel return line all the way from the rail to its destination.

Exactly correct.
Knowing all that why the return line to the pump if yours has a return to the tank.

I can't think of any reasonable answer to that question or why PCM thought it was a good idea.
You turn the key, Pumps kick on, system pressurizes and its ready to go. I see not reason for the second return.
I would block the second return to the pump and see if your start up hot issue goes away. I believe that is your plan and your waiting on fittings.
I think it will help with or without a new pump install.

I did a search for regulations on Marine Fuel Lines.
This is interesting and odd but explains what they attempted to do with the pump design on the GT40 system.

15. Fuel pumps on a marine engine must be designed to not leak fuel into the boat. Many are double diaphragm. Today most engines have electric fuel pumps. The pump must be mounted on the engine or within 12 inches of the engine. This minimizes the amount of fuel line that is under pressure. It also means that unlike newer cars the line from the tank to the engine is under negative pressure. In other words, the fuel is sucked to the pump rather than pushed to the pump. That way if there is a leak the engine just starves for fuel and stops. The fuel pump must be fire resistant.

16. Fuel lines from the pump to the carburetor must be metal or USCG Type A marine fuel hose. This hose is fire resistant. The hose from the tank to the pump can be USCG Type A or B. Type B is not fire resistant and is hard to find.

17. Fuel filters can not leak into the boat either and must be fire resistant.

18. Fuel tanks must also be fire resistant and pass a 3 PSI pressure test. Today most fuel tanks on gasoline powered boats are aluminum or plastic (Polyethylene). Both must pass all the requirements of the Coast Guard. Other materials are not prohibited but need to be built to specific standards. The tanks must not be integral with the hull.

19. The fill and vent hose can be USCG type B hose but again it's hard to find. You can use Type A. Also on cars fuel tanks and the whole fuel system are closed and under slight pressure. On boats this is unsafe. If a leak developed anywhere in the system it would literally empty the entire contents of the fuel tank into the bilge of the boat. So boat fuel systems are vented to the atmosphere to keep them at atmospheric pressure.

Since January 2011 the rules have changed somewhat due to environmental regulations. Fuel systems are now closed but not allowed to exceed a maximum pressure of 1 psi. This is achieved with a 1 psi pressure relief valve built into the vent line. The system also has a carbon canister to collect and scrub vapors. See Gasoline Fuel Systems http://newboatbuilders.com/pages/fuel.html and Fuel Tanks http://newboatbuilders.com/pages/fuel_tank.html

NOTE: GM engines use some of the same parts on both the auto and marine versions. For instance, truck cams are very much the same as cams on boats. However, if it is a fuel injected engine there may be a problem. Most fuel injected auto engines have a pump in the fuel tank that pressurizes the fuel lines. You don't want pressurized lines running through your boat, so you can't have the pump in the tank. On boats the fuel pump is near (within 12 inches) or on the engine and fuel is sucked to the engine rather than pushed. So how do you pressurize the fuel line so the engine will start quickly without having to crank it for several minutes? A time delay on the pump is allowed. By this I mean that on most marine fuel injected engines, when you turn on the ignition the electric pump comes on and pressurizes the short fuel line from the pump to the fuel injection system, it then shuts off until the engine starts, then the pump comes back on. Most marine fuel injected engines do not have a pressurized return line to the tank. They have a built in recirculating tank on the engine, and a gravity feed back to the tank.

More Thoughts on Marine Engines

A link to Indmars replacement. I don't see a return on this pump

https://www.bakesonline.com/searchresult.aspx?CategoryID=503&page=3

That's it in a nut shell

Gary, Gun Driver is working on this now. He supplied the picture I post, pictures come from a Master Craft forum if you can believe that.
I think we will know soon how a replacement Carter pump is working for Gun Driver.
Looking at this photo I can tell you the OE Pump was made by Carter, it is a geroter and turbine pump. The geroter ( gear pump design ) provides steady high pressure but does not prime well so they add the turbine to help it prime better.   The intake side of this pump has two intakes.   Geroter pumps are sensitive to pumping any dirt, dirt can lock them up so make sure your feed line has a filter on it, a good filter that is less than 20 micron size.    
The two bottom pump threaded connections are not pressure ports, they are both intake ports. Any pressure in these lines would be provided by the low pressure supply pump also a Carter design.
Every Automotive application I know of uses one feed line and one return line.   The second feed line to this High pressure pump comes from the Fuel Rail return line after the pressure regulator. The fuel rail return line also has a line that drains back into the gas tank on these boats so I see no reason for the second return line to the High Pressure pump.   Can anyone explain why the second return line would exist?   
If you want to stay similar to the factory an aftermarket pump could be installed and you could add a T in the feed line, metal or brass and threaded to maintain the factory second feed to the intake. ( aftermarket HPP pumps are $70-$135.00 a little cheaper than the OEM design at $650 that is not available ) The problem with this design is that it returns Hot fuel to the intake feed and fuel injection prefers cool fuel at the intake feed.
My only idea on this would be to help have constant supply to the HPP even if the boat is involved in rough water and the tank is splashing around and the feed is not constant.
Fuel injection demands a constant flow of fuel to work right. This idea is my WAG!

Mark do they or basically any simmiler pump,ie automotive fail is because of bearing failure? I remember at work a truck would get towed in and dropped off. Our mechanic being by himself could not push it in to the bay so he'd take a rubber hammer have one of us turn the key to start it and pound on the bottom of the tank and sure enough they would go. Always seemed that the tanks were just topped up too. Chevys went thru pumps like crazy,Fords went thru oil pans

Gary S wrote: Mark do they or basically any simmiler pump,ie automotive fail is because of bearing failure? I remember at work a truck would get towed in and dropped off. Our mechanic being by himself could not push it in to the bay so he'd take a rubber hammer have one of us turn the key to start it and pound on the bottom of the tank and sure enough they would go. Always seemed that the tanks were just topped up too. Chevys went thru pumps like crazy,Fords went thru oil pans

Gary the most common issue is dirt and dry starting. The bearings in these are fuel lubricated so any dry start will toast the pump. Engineering says the bearings/bushings will be damaged within 20 seconds on a dry start. Dry starts happen when cars are parked on a side hill, it does not have to be much slope if the car is low on gas.
Dirt contamination will damage the pump as it passes through. Any dirt will start wearing on the bushings because it all flows past the moving parts as it is pressurized.
I don't mind driving my car all the way to near empty when on the road if I know exactly when I will get gas. If I am heading home I fill up if I am below 1/4 tank to avoid this damage.   The third most common issue causing pump failure is bad connections to the battery. The pumps need 12 V plus to operate well. If the ground is bad or the power source is corroded the pump may only see 7 V and it will burn up.
Sometimes the pump has 12V when not running but when the load hits it the power source can drop off considerably.
If the pump is noisy, it is toast.   These are the ones that will respond to a good tap with the rubber hammer normally.   This band aid usually only works till you shut it off next time. Damaged bushings make them noisy. Tolerances are pretty tight so damaged parts can start rubbing on other parts making even more noise.
They usually fail over time, slowly getting louder till they lock up unless you run them dry when the process goes pretty fast.

Gun Driver, so far I have not seen a air separating check valve. Not in fuel or even brake ABS systems. If there was such a valve it would be really popular. You could eliminate bleeding brakes.
The pressure releaf valve on the fuel rail can bleed off a lot of fuel. At times that bleed off may be at 20 psi. Headed back to the tank.. I still scratch my head why this second line exists. I think we can figure it out.

I am of the thinking that when one replaces the fuel filter and does not fully fill the container with fuel and bleed the air that is trapped--there may be a possibility that LPP's are not failed but are being replaced needlessly.

I'm saying this because when I had a Nautiqie dealer replace my fuel filter, that's when all my troubles with starting erupted. I must have bled the schrader a dozen times before deciding to replace the LPP due to start and die issues I attributed to the LPP. Perhaps if I'd simply removed the FCT housing and filled it with fuel, or kept bleeding the trapped air from the valve, I'd have not needed a new LPP at only 500 hours of engine time.