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Mercury 2001 150xl Carb - Hard to start

R

Redwoolard

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Serial number 0T397825.
I have a 150 Mercury that is very hard to start. Once it starts, it runs good, idle may be a little rough but every one I have seen idles a little rough. Once you shut it off, the same thing - very hard to start. It doesn't matter if it is hot or cold. It doesn't matter if you try right then or wait a few minutes, It will not start without choking and sometimes you have to go WOT.
I have disassembled the carbs and cleaned them with spray cleaner but not soaked in carb cleaner. It did not make any difference. I did the link and sync on the carbs. The bottom carb was off a little and the oil setting was off just a bit. all set back to the book and still no difference.
I cleaned every ground/connection I could find and still no better.
I do not have a spark checker but I took them out and checked the spark at the plug and it looks very weak. I cleaned and regapped the plugs before checking. They aren't over a few months old. You can barely see the spark. Have to look real hard.
I did find 2 blown fuses going to the voltage regulators, replaced them. The motor was not keeping the batteries charged so this was probably the reason why - they did not blow when i cranked the motor after changing the fuses. The boat has two batteries that you can run separately or switch in parallel to the motor.
The motor cranks a little better when on both batteries but either battery will spin the motor fine.
Any suggestions?

Thanks in advance
 
Myself I would take the starter apart for simple inspection and an ohm test on the armature.--------Slow cranking will mean weak / no spark.----------This costs no $$ to do.------------Some will argue and have a different opinion / approach to this problem.
 
Red woolard, your engine has to rotate at least 200-300 rpms to start,fully charge batteries overnight slowly,test again. post#2 you need 200-300 rpms to generate a good blue lightning snap!
 
I am pretty sure it is rotating plenty fast enough, based on other boats I have owned in the past. I can check the starter if I need to but it spins good, just super hard to crank. I have a dvA adapter coming today. Can I check the voltage going to the coils by unplugging the connector at the coil and checking at the connector? The book shows using a harness adapter to check it?
 
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Switching the battery switch while engine running will blow the rect/reg fuses. Also that engine has CDM modules. If it wont start unless you choke it its a fuel related issue. Make sure the thermo valve on head is working as it controls air to carbs..
 
Had exactly same issue, then would not turn off, whole issue was harness throwing curren into kill switch so weak spark, rough wouldn't idle, hard to start. All tests had good continuity. Have 2 motors so eventually swapped harness to prove up. New harness goes great now.
Redwoolard said:
Serial number 0T397825.
I have a 150 Mercury that is very hard to start. Once it starts, it runs good, idle may be a little rough but every one I have seen idles a little rough. Once you shut it off, the same thing - very hard to start. It doesn't matter if it is hot or cold. It doesn't matter if you try right then or wait a few minutes, It will not start without choking and sometimes you have to go WOT.
I have disassembled the carbs and cleaned them with spray cleaner but not soaked in carb cleaner. It did not make any difference. I did the link and sync on the carbs. The bottom carb was off a little and the oil setting was off just a bit. all set back to the book and still no difference.
I cleaned every ground/connection I could find and still no better.
I do not have a spark checker but I took them out and checked the spark at the plug and it looks very weak. I cleaned and regapped the plugs before checking. They aren't over a few months old. You can barely see the spark. Have to look real hard.
I did find 2 blown fuses going to the voltage regulators, replaced them. The motor was not keeping the batteries charged so this was probably the reason why - they did not blow when i cranked the motor after changing the fuses. The boat has two batteries that you can run separately or switch in parallel to the motor.
The motor cranks a little better when on both batteries but either battery will spin the motor fine.
Any suggestions?

Thanks in advance
Click to expand...
 
Update.
Checked all CDM's for spark while cranking - spark will jump 1/4"-5/16" - not the 7/16" the book says it should.
I am pretty sure the Motor is spinning plenty fast enough. I checked the voltage drop while cranking and at the starter, it drops to 9.3 volts. Is this normal?
I have not pulled the starter and done a resistance test but it spins pretty good for a 150 mercury.
Trigger resistance is spot on - within the ranges in the book.
Stator resistance test shows 260 ohms between the green/white and white/green. The book says it should be between 380-430.
The idle adjustment screws were way off. I set them per the manual and at least, I can crank it now easier, but you have to do WOT to get it to crank. It cranks a lot easier now with that adjusted but still not like it should. The book says out 1 1/4 turns out from closed. I had one only a half turn and three that were at 1 3/4 turns. the other 2 were less than 1 turn out.
We checked the enricher valve and it works when you push the key in. It is leaking around the top so I am going to replace it.
There is a black/white wire coming from the ignition box that is not connected to anything and I do not see anything glaring that matches it?
Any suggestions based on what i just found? Is the low stator resistance an issue?
 
Voltage on all of the CDM's is 90-92 volts. I checked the stator resistance again and it is 266. Book value says 380-430
Is there anything else I should check or should I replace the stator?
Voltage at the starter would drop to 9.7 volts while doing this test. Is that normal?
 
Customer had the same engine with the same problem. The engine would only start with a jump pack hooked right to the starter. The pack gave the engine just a little more cranking RPM and it would start.

The stator was weak. I replaced the stator and the problem was solved.

I am not saying your stator is weak. I am pointing out that cranking rpms are important.

9.7 volts while cranking is low. You may not be spinning the engine fast enough.
 
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Pulled the flywheel to look at the stator. the total resistance on the green/white to white/green is still 266. If you check the terminals coming off of each of the three coils - they test 138, 76, 52. Shouldn't they all be the same? If you take 138 X 3 you come up within the specs - (380-430)
I used a jumper cable directly to the solenoid to get good voltage at the starter but it made little difference on the voltage going to the CDM. It was max 111 on the 2 I tested. I think I have a dirty connection at the battery switch.
The trigger has a couple of small cracks on the top. Is that normal? All resistance checks on the trigger assembly are good.
Thoughts? Replace stator and possibly trigger?
 
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