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Would Love Some Help

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pytcokid

New member
Alright everybody I am inquiring about a 5.7L Alpha 250hp inboard motor on my aunts 2002 model year boat. I am a mechanic and know how to work on engines on cars but boats are alien to me. Having said that a motor is a motor and she asked me to help and I said I would try. So here is my problem with her boat. It wont start. The batteries are good, I just checked them, spark plugs aren't great but will suffice until I replace them tomorrow morning. The boat does turn over constantly but wont start. It ran just fine last year but hasnt been started this year after it sat over the winter. It does seem to be getting a very large amount of condensation on the engine every day no matter the temp or weather. I am worried about a moisture problem. Also I dont believe, but I dont know how to check, that the fuel is being pumped into the system, so any advice on that would help. It does have a carburetor so I hope that info helps out with any advice you can give.

So if anyone could give me any advice or tips on where to look next I would greatly appreciate it. Tomorrow morning I am going to spray some starter/ether into the air filter to see if i can get it running, any help I could get before then would be amazing.

I know I am a total noob on the forum here guys and I am sorry if i posted in the wrong section, like I said this is alien to me. Please dont beat me up too harshly, I know noob questions can be a real bother when it comes to the forums.

Anyway thanks for any help or advice ladies and gents, hope to hear from someone soon.
 
pull a plug wire use a spark checker or known good plug and make sure you have fire, pull the spark arrestor look and see when you give it gas does fuel squirt down carb......
Check your man overboard switch at helm, could also be a bad electrical connection and your fuel pump is not running while starter is engaged........
 
midcarolina said:
pull a plug wire use a spark checker or known good plug and make sure you have fire, pull the spark arrestor look and see when you give it gas does fuel squirt down carb......
Check your man overboard switch at helm, could also be a bad electrical connection and your fuel pump is not running while starter is engaged........
Click to expand...


thank you, i will check those things first thing when i have light in the morning. I did check down the carb tonight after we tried starting it a few times after a few checks, and it remained bone dry all night, hope that helps.
 
Ok I got back to the boat this morning after picking a few things up. I shot some ether into the carb and was going to start it so I could look down into the carb and nothing. There were no hums buzzes or clicks. No sylinoid sounds, no fuel pump sounds. I rechecked the battery, good, I check connections, good, distributor cap and wires, good, I manually cranked the engine, not frozen, and the accessories work. I want to say my ignition switch or man over board switch is bad and causing the failure of starting. Any ideas?
 
Mercruiser uses two starter solenoids,

One on the starter and a second one (slave solenoid) typically mounted on the top left side of motor (facing it from the inside of the boat)

Use a test light and go to ignition switch, one wire should be battery + (red wire), other should be purple (ignition ON) and the other should be yellow with red stripe (crank)

Turn key to on position and see if you have power to purple, if yes good. This also would show up as guages working.

now turn the key to the crank position and see if you have power to the yellow with red stripe, if yes good. Now the neutral saftey switch that is in the shift control is in series with the crank wires so if NO neitral the crank signal will not get to the slave solenoid so it could be a bad switch or just move the shifter a bit to see if you get the switch to close.

Now find the slave solenoid and use a jumper wire and go from the large red wire (top terminal) to the small yellow wire (small terminal) this should crank the starter. If not the solenoid is bad.
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USCG regs require a low oil pressure switch that interrupts the fuel pump power in the absence of oil pressure.
Along with this comes the need for a "start-by-pass" circuit.
This circuit provides fuel pump relay triggering power during engine cranking only until oil pressure is achieved.
Once oil pressure is achieved, the start-by-pass circuit is no longer needed to trigger the fuel pump relay.

While the starter motor is being energize, take a voltage reading at the fuel pump's power terminal.
You may also want to power the fuel pump terminal as to see if the pump is actually working.
Power the realy electro magentic side, and check the output side of the relay.


When you test for spark quality, place a know-to-be-good plug wire directly into the ignition coil. (this way you'll see 8 spark events for two full crankshaft revolutions.... not just a single spark event per two full revolutions)
Place a know-to-be-good spark plug into the plug wire boot, and make certain that the plug body makes a good negative contact with the engine block.

Caution: Watch out for explosive fuel vapors while working in an engine bay!

You should see a bright blueish/whitish spark with a crisp audible snap to it.

Fuel/air delivery....... correct cylinder pressure..... correctly timed ignition spark.... and the Engine should fire up.


.
 
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Ok, there is no power at the ignition switch, gauges don't come on, no crank. I used the jump wire and the engine did crank. But while I was cranking it there was no fuel running into the carb. It's bone dry. I am assuming that is because the ignition switch is bad and not powering the pump? I will also check that start by pass if I can but that is a little out of my knowledge of boats I might take it to an actually marine mechanic to check the start by pass.
 
Blown ignition fuse inline or on dash or breaker........follow red wire from ignition switch backwards until you find why you have no power.

Also do not get wound up with a fuel pump/low oil pressure switch.

First determine if you have a mechanical fuel pump or electric fuel pump. This is a CARBED motor...........
Also with no ignition ON/power at the ignition switch then NO 12 volts to the ignition system...........gas or not.......


If you have a electric fuel pump then when you achieve power to the ignition switch it will apply power to the fuel pump when cranking and when the key is returned to the run position then the oil pressure switch will take over so if oil pressure drops it will kill the fuel pump.
 
...............

kghost said:
Also do not get wound up with a fuel pump/low oil pressure switch.
First determine if you have a mechanical fuel pump or electric fuel pump.
I'm fairly certain that the mechanical fuel pumps have long since been eliminated in lieu of the electric.
5.7L Alpha 250hp inboard motor on my aunts 2002 model year boat.
Click to expand...

This is a CARBED motor...........
I questioned that also.... but then I went back to confirm.
I did check down the carb tonight after we tried starting it a few times
Click to expand...

Also with no ignition ON/power at the ignition switch then NO 12 volts to the ignition system........... gas or not.......
I fully agree...... that is why I suggested to check or re-set the red button circuit breaker.

If you have a electric fuel pump then when you achieve power to the ignition switch it will apply power to the fuel pump when cranking and when the key is returned to the run position then the oil pressure switch will take over
Precisely!

so if oil pressure drops it will kill the fuel pump.
Yes........... this is a USCG reg.
Click to expand...


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