1998-2000 Custom Boat Fuel prime issue (5.7L Mercruiser Inboard/Stern Drive w/ Alpha One Mercruiser outboard Drive)

[Allenk13734]

I have recently acquired, a sitting, in climate controlled storage, handmade boat with a mercruiser 5.7l. My problem is that it sat for 4-5 Years. Which is fine, because the engine was pickled before it sat, but it does not build fuel pressure. it has a clear filter housing with an inline fuel filter going to it. The sightglass will fuel about 3/4 way up with gas but not all the way. The engine runs if I squirt a bit of starter fluid/gas down the carburetor but will not fire off of its own tanks. I've emptied the tanks and refilled with fresh gas. I'm a classic car mechanic, and not a boat mechanic by any means. Anyone have any insight?

 

[Scott06]

I have recently acquired, a sitting, in climate controlled storage, handmade boat with a mercruiser 5.7l. My problem is that it sat for 4-5 Years. Which is fine, because the engine was pickled before it sat, but it does not build fuel pressure. it has a clear filter housing with an inline fuel filter going to it. The sightglass will fuel about 3/4 way up with gas but not all the way. The engine runs if I squirt a bit of starter fluid/gas down the carburetor but will not fire off of its own tanks. I've emptied the tanks and refilled with fresh gas. I'm a classic car mechanic, and not a boat mechanic by any means. Anyone have any insight?

Would look on top of fuel tank pick up tube usually in the barbed fitting where it transitions to fuel hose there will be an anti siphon valve. Is a small spring loaded valve that can stick closed. In event of a fuel line rupture it prevents the gas tank siphoning out to bilge.

would also look for leaks on suction side of fuel pump, hose clamp loose or fuel line dry rotted. Is fuel filter housing sealing up ? Is this a marine fuel filter or cheap disposable inline clear filter Like comes with edlebrock carbs? If one of the disposable ones take it out and see if you get fuel. These cheap ones are not made for marine applications

is this a mechanical or electric fuel pump? The clear fuel filter is not an oem mercruiser set up as they use canister filters .

 

[Allenk13734]

It does have a cartridge style fuel filter on it, that then goes to an electric pump, so top down order is carburetor/throttle body (I'm not sure) --> electric fuel pump --> cartridge fuel filter housing & filter --> inline fuel filter --> tank selector valve --> one of two 50 Gallon tanks. It does not seem to be a small inline filter provided with an automotive carbutetor but an aftermarket sight glass filter, should I remove the cartridge filter and replace it/fill it with gas/fill new one with gas and delete the other inline filter and see if it'll prime then? I know it's not a spark issue because I checked spark at all the plugs individually and it has spark, it tries to kick over but doesn't seem to be getting any gas.

 

[Allenk13734]

Refer to post below, but the two tanks it has on it are two custom fifty gallon aluminum fuel cell, it appears to be just a barbed fitting going into the tanks.

Would look on top of fuel tank pick up tube usually in the barbed fitting where it transitions to fuel hose there will be an anti siphon valve. Is a small spring loaded valve that can stick closed. In event of a fuel line rupture it prevents the gas tank siphoning out to bilge.

would also look for leaks on suction side of fuel pump, hose clamp loose or fuel line dry rotted. Is fuel filter housing sealing up ? Is this a marine fuel filter or cheap disposable inline clear filter Like comes with edlebrock carbs? If one of the disposable ones take it out and see if you get fuel. These cheap ones are not made for marine applications

is this a mechanical or electric fuel pump? The clear fuel filter is not an oem mercruiser set up as they use canister filters .

 

[Scott Danforth]

That inline plastic filter is not legal, and since it's sitting in front of a 20 micron water separating filter, it's pretty useless

Make sure the fuel pump is working.

Run the motor off a small 1-3 gallon fuel tank first. You can chase the system upstream of the fuel filter from there. Pull the anti siphon valve and pickup tube to check them

 

[Scott06]

It does have a cartridge style fuel filter on it, that then goes to an electric pump, so top down order is carburetor/throttle body (I'm not sure) --> electric fuel pump --> cartridge fuel filter housing & filter --> inline fuel filter --> tank selector valve --> one of two 50 Gallon tanks. It does not seem to be a small inline filter provided with an automotive carbutetor but an aftermarket sight glass filter, should I remove the cartridge filter and replace it/fill it with gas/fill new one with gas and delete the other inline filter and see if it'll prime then? I know it's not a spark issue because I checked spark at all the plugs individually and it has spark, it tries to kick over but doesn't seem to be getting any gas.View attachment 404601View attachment 404602View attachment 404604

yeah I would remove the redundant disposable filter replace that section with new hose.

some of the antisiphon valves are inside what looks like a barbed fitting so I would just verify you have fuel freely to the fuel tank valve.

Have you checked the pump is running while cranking? not sure if this has stock merc wiring harness on it but I believe it will get power off the starter during cranking and then off the purple wire via the oil pressure switch (two on these engines one for OP alarm one to cut off fuel pump power if engine is not running with ignition on).

What does the contents of the canister filter look like?

 

[Allenk13734]

That inline plastic filter is not legal, and since it's sitting in front of a 20 micron water separating filter, it's pretty useless

Make sure the fuel pump is working.

Run the motor off a small 1-3 gallon fuel tank first. You can chase the system upstream of the fuel filter from there. Pull the anti siphon valve and pickup tube to check them

I don't have any small fuel tanks, but the fuel pump is working. Unfortunately the starter that's been on there since approximately 1998 decided today that it didn't want to click anymore so I will have to wait for a new starter to come in from mercruiser before I can attempt to prime the fuel system again as I'm not sure how to jump the fuel pump and I'm not keen on just wiring a hot lead to the fuel pump amidst potential gas fumes, I've unplugged the Fuel lines, and while not sure if this is legal, there does not appear to be an anti siphon valve inside the barbed fitting.

 

[Scott Danforth]

Your starter issue is most likely a bad connection

 

[Allenk13734]

Your starter issue is most likely a bad connection

Starter ended up being completely dead, I pulled it and jumped it with a known good battery I had laying around, and found out that it was just toast. I guess after the starter sat for 5ish years it didn't wanna work. I replaced it with a new starter, and noted that the new starter spun the engine over 2-3ish times faster, so I'm wondering if that starter was even good the day prior, or if the new starter is just that much more powerful.

 

[Allenk13734]

Your starter issue is most likely a bad connection

I noted your comment about an Oil Pressure Alarm, to my knowledge every time I've turned the key on this I have never noticed an Alarm, so I went digging through the dash and found that there were two unplugged wires, so I plugged them in. (To my knowledge, this is infact the oem mercruiser wiring harness, the guy I got this boat from is a professional carpenter of 50+ years who decided twenty years ago to build a boat for the heck of it. He then went to a dealership and had a Mercruiser technician outfit the boat with the Mercruiser 5.7l I/O) He had previous issues with the on/off/killswitch not working, and had messed around with the wiring in the dash a little, so I'm guessing he accidentally loosened up the alarm. Unfortunately while trying to get the fuel filter off to check its contents, I had to remove the fuel filter housing and put it in a vice to punch a screw driver through because it was on that tight. there was a bit of corrosion on the sealing surface that had adhered itself to the rubber gasket on the fuel filter, and I don't have the nicest of oil filter wrenches and it ended up caving the filter in at the bottom leading to me doing this. I have not tested whether or not the fuel pump will prime with this, as by the time I had figured out there was no alarm and remedied such I had removed the fuel filter, I will buy a new fuel filter in the morning and try it tomorrow morning, wish me luck and thank you for the advice. quite frankly, I would have never figured out the fuel pump has a shut off conected to the Oil Pressure Sensor/OPS Alarm.

 

[Scott06]

I noted your comment about an Oil Pressure Alarm, to my knowledge every time I've turned the key on this I have never noticed an Alarm, so I went digging through the dash and found that there were two unplugged wires, so I plugged them in. (To my knowledge, this is infact the oem mercruiser wiring harness, the guy I got this boat from is a professional carpenter of 50+ years who decided twenty years ago to build a boat for the heck of it. He then went to a dealership and had a Mercruiser technician outfit the boat with the Mercruiser 5.7l I/O) He had previous issues with the on/off/killswitch not working, and had messed around with the wiring in the dash a little, so I'm guessing he accidentally loosened up the alarm. Unfortunately while trying to get the fuel filter off to check its contents, I had to remove the fuel filter housing and put it in a vice to punch a screw driver through because it was on that tight. there was a bit of corrosion on the sealing surface that had adhered itself to the rubber gasket on the fuel filter, and I don't have the nicest of oil filter wrenches and it ended up caving the filter in at the bottom leading to me doing this. I have not tested whether or not the fuel pump will prime with this, as by the time I had figured out there was no alarm and remedied such I had removed the fuel filter, I will buy a new fuel filter in the morning and try it tomorrow morning, wish me luck and thank you for the advice. quite frankly, I would have never figured out the fuel pump has a shut off conected to the Oil Pressure Sensor/OPS Alarm.

Not uncommon if the filter canister has been on there to have to use some azz to remove it. I had to do the same thing on my boat. It was 10-11 years old and the fuel filter had never been changed... put the filter housing in a vice, cut the filter in half with tin snips so I could get a good pair of vice grips on it and hit the vice grips with a hammer.
see attached wiring digram this is off a V6 but the 5.7 carbed engines use the same fuel pump and filter set up.
as mentioned above there are two oil pressure switches so the one driving the fuel pump is not the same as with the audible alarm that should come on when ignition is on but engine is not running.
the oil pressure switches for the fuel pump is number 7 you can see where the starter powers the fuel pump in parallel until the key goes to run which powers the purple wire and goes through oil pressure switches for the.

you can see on RH side of deg that the warning alarm switch is different as is the OP sender for the gauge.

 

[Allenk13734]

Not uncommon if the filter canister has been on there to have to use some azz to remove it. I had to do the same thing on my boat. It was 10-11 years old and the fuel filter had never been changed... put the filter housing in a vice, cut the filter in half with tin snips so I could get a good pair of vice grips on it and hit the vice grips with a hammer.
see attached wiring digram this is off a V6 but the 5.7 carbed engines use the same fuel pump and filter set up.
as mentioned above there are two oil pressure switches so the one driving the fuel pump is not the same as with the audible alarm that should come on when ignition is on but engine is not running.
the oil pressure switches for the fuel pump is number 7 you can see where the starter powers the fuel pump in parallel until the key goes to run which powers the purple wire and goes through oil pressure switches for the.

you can see on RH side of deg that the warning alarm switch is different as is the OP sender for the gauge.

Gotcha, small question, this engine does infact have a knock sensor, does that affect anything about the wiring harness and it's functions?

 

[Scott Danforth]

The knock sensor is wired to the ignition module. It does not impact rigging wiring from the cannon plug to the controls

 

[Scott06]

Gotcha, small question, this engine does infact have a knock sensor, does that affect anything about the wiring harness and it's functions?

As Danforth laid out doesn't impact what you are working through here. You can google a wiring digram with the knock system. it has sensor located on a Y at the block drain, wiring up to the knock module that piggybacks the ignition module and wiring between them. The knock module sends a 9 vdc signal to the ignition module when it is not knocking. if the 9 v is removed the IM will retard timing.

if you had an issue say not reaching full power or rpm and you saw that total ignition advance is not happening it is something to look at but for lack of fuel it has no effect .

Do yourself a favor and get the factory manuals for your engine and drive. A merc dealer or merc tech support can tell you what manual you need off your serial number. I bought used ones on ebay for $35-50 each