1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

[BigOtis]

Hi guys, Newbie to site here, thanks for the welcomes!!! My question is, I recently purchased my first boat, 1997 Regal, 3.0l Mercruiser LX. I am having fuel issues I think with fuel getting to carb. The boat idles just fine but when throttling up to come on plane the boat will plane out, run a few hundred yards and engine dies. Then i can start it back up and it does the same thing. Strange this thing will idle and run fine with muffs on it, you can even rev it up and down and put it in and out of gear just fine. But soon as you put it in the lake and put a load on it the the engine trouble shows up?

I have so far checked the obvious: Fuel vent is ok. Carburetor just got rebuilt two weeks ago by dealership. Fuel filter has been changed. I also added an additional fuel water separator system. What are your thoughts?

I am wondering if it is a fuel pump issue? If so can you guys tell me if you think this might be the issue and what part number would replace the fuel pump on his engine now.

 

[alldodge]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

Hi guys, Newbie to site here, thanks for the welcomes!!! My question is, I recently purchased my first boat, 1997 Regal, 3.0l Mercruiser LX. I am having fuel issues I think with fuel getting to carb. The boat idles just fine but when throttling up to come on plane the boat will plane out, run a few hundred yards and engine dies. Then i can start it back up and it does the same thing. Strange this thing will idle and run fine with muffs on it, you can even rev it up and down and put it in and out of gear just fine. But soon as you put it in the lake and put a load on it the the engine trouble shows up?

I have so far checked the obvious: Fuel vent is ok. Carburetor just got rebuilt two weeks ago by dealership. Fuel filter has been changed. I also added an additional fuel water separator system. What are your thoughts?

I am wondering if it is a fuel pump issue? If so can you guys tell me if you think this might be the issue and what part number would replace the fuel pump on his engine now.

:welcome: to iboats

I take it you added the fuel/water separator before the fuel pump? Where is the filter located as far as height to the fuel pump? Is it down low or up high?

 

[BigOtis]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

:welcome: to iboats

I take it you added the fuel/water separator before the fuel pump? Where is the filter located as far as height to the fuel pump? Is it down low or up high?

Sorry if this post keeps repeating, I am trying to figure out how to answer with quote...

That is correct I just put the fuel/water separator on a few days ago.... I have not bought and put in a fuel pump yet.... The fuel/water separator is mounted on a bulkhead slightly above in relation to the fuel pump.

 

[alldodge]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

Sorry if this post keeps repeating, I am trying to figure out how to answer with quote...

That is correct I just put the fuel/water separator on a few days ago.... I have not bought and put in a fuel pump yet.... The fuel/water separator is mounted on a bulkhead slightly above in relation to the fuel pump.

With the pump only being slightly above there should be no issue with pump being able to lift the fuel, just checking to make sure.

I would suggest putting a fuel pressure gauge between the pump and carb by using a tee-fitting. Pressure should be between 4-8 psi.

If it does turn out you need a fuel pump the part number is 8M0073435.
Below is a link that shows the breakdown.
http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=809870 96&ivar=images/COMMON/8165.png&inbr=2330&bnbr=60&bdesc=Fuel+Pump+and+Carburetor

 

[BigOtis]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

With the pump only being slightly above there should be no issue with pump being able to lift the fuel, just checking to make sure.

I would suggest putting a fuel pressure gauge between the pump and carb by using a tee-fitting. Pressure should be between 4-8 psi.

If it does turn out you need a fuel pump the part number is 8M0073435.
Below is a link that shows the breakdown.
http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=809870 96&ivar=images/COMMON/8165.png&inbr=2330&bnbr=60&bdesc=Fuel+Pump+and+Carburetor

Thanks Dodge, you da man.... Is that part number for the pump the original part or an OEM. Carter, Mallory, Sierra??? Also, where can I find a fuel pressure gauge? Im just a novice at this so I dont own a gauge.... I also thought about un-hooking the fuel lines from the fuel pump and hooking them to an external portable 5 gallon gas can and running the boat that way to make sure there is absolutely no water or trash in main on board fuel tank. This would isolate the fuel at least that far. what you think of that?

Also, will the OEM fuel pump be a bolt on and go situation? I have read on the board here of people having trouble with this engine and OEM fuel pumps, the arm of the fuel pump extending too far into the engine cavity and upping the pumping pressure while running. Some folks were saying they had to shim the pump away from block to put the arm in the correct place? You heard of this?

 

[alldodge]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

Thanks Dodge, you da man.... Is that part number for the pump the original part or an OEM. Carter, Mallory, Sierra??? Also, where can I find a fuel pressure gauge? Im just a novice at this so I dont own a gauge.... I also thought about un-hooking the fuel lines from the fuel pump and hooking them to an external portable 5 gallon gas can and running the boat that way to make sure there is absolutely no water or trash in main on board fuel tank. This would isolate the fuel at least that far. what you think of that?

Also, will the OEM fuel pump be a bolt on and go situation? I have read on the board here of people having trouble with this engine and OEM fuel pumps, the arm of the fuel pump extending too far into the engine cavity and upping the pumping pressure while running. Some folks were saying they had to shim the pump away from block to put the arm in the correct place? You heard of this?

The part number is the Mercruiser number (OEM). The Sierra number and link is shown below. Running the boat from an external can is a good plan since there could be a contamination or restriction inline. I'm thinking there is either a restriction in the fuel system or a weak fuel pump. To measure the fuel pump pressure get a Vacuum/fuel pressure gauge from any auto store, they are fairly cheap. Get a 5/16 plastic fitting while your at it, a few hose clamps and an short piece of fuel line. Remove the carb end of the fuel line and install the tee, then connect the gauge.

BTW, I have not heard of an issue with the fuel pump unless someone installed the wrong pump

Fuel Pump - Sierra

Vac/fuel pressure gauge

 

[BigOtis]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

The part number is the Mercruiser number (OEM). The Sierra number and link is shown below. Running the boat from an external can is a good plan since there could be a contamination or restriction inline. I'm thinking there is either a restriction in the fuel system or a weak fuel pump. To measure the fuel pump pressure get a Vacuum/fuel pressure gauge from any auto store, they are fairly cheap. Get a 5/16 plastic fitting while your at it, a few hose clamps and an short piece of fuel line. Remove the carb end of the fuel line and install the tee, then connect the gauge.

BTW, I have not heard of an issue with the fuel pump unless someone installed the wrong pump

Fuel Pump - Sierra

Vac/fuel pressure gauge

Dodge, Thanks so much for the info. Ill give his a try.

 

[havoc_squad]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

Also, will the OEM fuel pump be a bolt on and go situation? I have read on the board here of people having trouble with this engine and OEM fuel pumps, the arm of the fuel pump extending too far into the engine cavity and upping the pumping pressure while running. Some folks were saying they had to shim the pump away from block to put the arm in the correct place? You heard of this?

I can comment about this personally, the solution nearly 100% of the time of the 3.0L fuel pump over-pressure is not using the right Mercruiser gasket part for the fuel pump. There are several marine service shops that order generic replacement marine parts, and don't check serial number of gasket parts that come with the pump or are a seperate item to verify the needed parts.

The mix-up occurs when they assume the thin gasket that goes with the pump or is ordered is the correct one, instead of part cross-referencing. The thin gasket is usually for the V6/V8's that use the same mechanical fuel pump due to the arm needing to reach deeper in the block. The 3.0L's require a cork gasket to give them about 1/8 inch seperation of the fuel pump from the engine block.

Regarding the flexible threaded fuel hose for the testing, definitely recommended. It's a royal pain to try to fit that pressure test fitting with the OEM steel fuel line. Most of the times it can be done, but if you have a brass fitting very soft and brittle, you may mess it up.

 

[BigOtis]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

Hey guys, thanks for all the good help.... I found my fuel issue. It was the supply hose to my fuel pump from my water separator. Ethanol had eaten the lining in the hose up and the hose collapsed right at the nipple of the fuel pump causing about a 90% blockage in the line.

 

[alldodge]

Re: 1997 Mercruiser 3.0l LX - Fuel Issue / Fuel Delivery to Carb

Sounds great glad you found the issue. :thumb: