Engine turns over perfectly but just will not crank

Thread starter sunny_fun
Start date Aug 9, 2011

S

sunny_fun

Cadet

Aug 9, 2011

#1

I have a mercrusiser i/o engine serial #: 0f70080

Yesterday on the water we accidentally yanked the kill switch lanyard and it killed the motor. since that point we have not been able to get the engine to crank, but it sounds like its turning over very well and sometimes it even makes that noise like its about to catch and crank.

things we have tried:
- checked to make sure we put back the lanyard properly and its in the on position
- checked the circuit breaker button and it was not popped out
- checked battery
- checked fuel pump
- looked into carb while trying to crank and it was getting gas

at this point we are stumped!!!

Erika

thumpar

Admiral

Aug 9, 2011

#2

Re: Engine turns over perfectly but just will not crank

Check for voltage on the coil.

S

sunny_fun

Cadet

Aug 9, 2011

#3

Re: Engine turns over perfectly but just will not crank

voltage on coil is good....

K

Kurt V

Seaman Apprentice

Aug 9, 2011

#4

Re: Engine turns over perfectly but just will not crank

Start with what caused the problem, the kill switch. Might be a bad connection. Pull the switch out and let it pop back in a couple of times then see if it starts. If that doesn't work, check the wiring on the switch and see if something is loose.

S

sunny_fun

Cadet

Aug 9, 2011

#5

Re: Engine turns over perfectly but just will not crank

I agree I think your right, but we have jiggled the switch, turned it on and off, and checked the wiring. Alll with no luck.....

E

ErikF

Petty Officer 1st Class

Aug 9, 2011

#6

Re: Engine turns over perfectly but just will not crank

Do you have a spark tester? Going through the ignition systems would be my next step.

Don S

Honorary Moderator Emeritus

Aug 9, 2011

#7

Re: Engine turns over perfectly but just will not crank

Since this happened while you were running, and assuming you were on plane when it happened, I would suggest you pull the plugs and check for water. You may have enough water to foul the plugs and keep them from firing, but enough to drown the plugs and keep them from firing.
When you get the plugs out, pull the coil wire out of the distributor cap and ground it so it won't spark. Then open the throuttle to wide open and crank the engine over and blow all the oil and water (if any) out of the cylinders.
Then dry the plugs and put them back in. Then try to restart it.

If no start, it may also be flooded (gas). Move the throttle to WOT and try.

LX Kid

Ensign

Aug 9, 2011

#8

Re: Engine turns over perfectly but just will not crank

sunny_fun said:
voltage on coil is good....

What is meant when you say "voltage on coil is good?" Does that mean when coil high tension lead is pulled out of the distributor and held away from engine metal it jumps a nice clean blue spark? Asuming you have points and condenser in the distributor, did you check the point gap? What is the voltage on the "+" side of the coil when the points make it fire? If you have air, gas and spark "it will run," short of the timing chain breaking or being flooded.

S

sunny_fun

Cadet

Aug 9, 2011

#9

Re: Engine turns over perfectly but just will not crank

Don't have a spark tester but could easily run and buy one from the auto place down the street and test it. However, I'm just so baffled that it has been running perfect (just replaced manifolds, risers, fuel pump, fuel filter, oil change, new plugs and wires, new trim hoses) and we have had no problems until that kill switch lanyard got yanked.

S

sunny_fun

Cadet

Aug 9, 2011

#10

Re: Engine turns over perfectly but just will not crank

LX Kid said:
What is meant when you say "voltage on coil is good?" Does that mean when coil high tension lead is pulled out of the distributor and held away from engine metal it jumps a nice clean blue spark? Asuming you have points and condenser in the distributor, did you check the point gap? What is the voltage on the "+" side of the coil when the points make it fire? If you have air, gas and spark "it will run," short of the timing chain breaking or being flooded.

Well I used a little a 12v light tester and follwed instructions of what to look for when using the tester and it tested fine...

Don S

Honorary Moderator Emeritus

Aug 9, 2011

#11

Re: Engine turns over perfectly but just will not crank

You do NOT need a spark tester to check for spark.
Pull the coil wire out of the distributor cap. Hold the end of the wire 3/8 to 1/2" from a good clean ground (not paint) and crank the engine. You should get a bright blue spark Snapping across the gap.

LX Kid

Ensign

Aug 9, 2011

#12

Re: Engine turns over perfectly but just will not crank

sunny_fun said:
Well I used a little a 12v light tester and follwed instructions of what to look for when using the tester and it tested fine...

Did you do the other things I mentioned? They would be a very good "quick" test in the troubleshooting process.

S

sunny_fun

Cadet

Aug 9, 2011

#13

Re: Engine turns over perfectly but just will not crank

Don S said:
Since this happened while you were running, and assuming you were on plane when it happened, I would suggest you pull the plugs and check for water. You may have enough water to foul the plugs and keep them from firing, but enough to drown the plugs and keep them from firing.

Yes we were planed out and going along great then the lanyard got stuck on the drivers shirt when turned it came out and we stopped. So when you say the plugs may have water in there, how would it have gotten there? water rushing in from the back of the boat? we inspected all the plugs and the distributor and did not see any water but we will go through the steps anyways just to be sure, cause it sure can't hurt at this point! Thanks

LX Kid

Ensign

Aug 9, 2011

#14

Re: Engine turns over perfectly but just will not crank

sunny_fun said:
Don't have a spark tester but could easily run and buy one from the auto place down the street and test it. However, I'm just so baffled that it has been running perfect (just replaced manifolds, risers, fuel pump, fuel filter, oil change, new plugs and wires, new trim hoses) and we have had no problems until that kill switch lanyard got yanked.

Try by-passing the kill switch, electrically, being you probably don't have test meter and see if it will start. I don't know if the kill switch opens the circuit or not, probably does, so jump across the switch.

S

sunny_fun

Cadet

Aug 9, 2011

#15

Re: Engine turns over perfectly but just will not crank

LX Kid said:
Did you do the other things I mentioned? They would be a very good "quick" test in the troubleshooting process.

Yes as Don S also suggested I'm going to pull out the coil and check for the nice blue spark and check the point gap. what you said is very true, air+gas+spark= running engine. so since I know I have gas and its getting plenty of air, it must be the spark.

Thanks all!!! I am gonna go do some of these tests and come back!

S

sunny_fun

Cadet

Aug 9, 2011

#16

Re: Engine turns over perfectly but just will not crank

LX Kid said:
Try by-passing the kill switch, electrically, being you probably don't have test meter and see if it will start.

How would I go about just bypassing the kill swith? Just simply unwire it and try cranking the boat with it unwired?

LX Kid

Ensign

Aug 9, 2011

#17

Re: Engine turns over perfectly but just will not crank

sunny_fun said:
How would I go about just bypassing the kill swith? Just simply unwire it and try cranking the boat with it unwired?

Jumper across the terminals, where it's hooked up, and I think this will simulate the kill switch circuit. If it starts then that means the switch is bad or connections on the switch are bad. You know it's not every day that a kill switch gets used and it may have built up corrosion on the contacts.

D

dccordell

Chief Petty Officer

Aug 9, 2011

#18

Re: Engine turns over perfectly but just will not crank

As far as I know, the kill switch is normally closed, allowing the current to flow to the coil from the ignition switch. Pull the lanyard, and the circuit opens and the coil gets no power, so no spark, engine dies.

You could bypass testing the kill switch if you just do the spark test as they mentioned earlier... by pulling the high tension lead out of the distributor (not the coil) and holding it near a ground and looking for spark as you turn over the engine with the key (get someone to turn the key while you look for spark). If there is a spark, then you know that the kill switch is ok. If you don't see a spark, then you should start finding out why.

S

sunny_fun

Cadet

Aug 9, 2011

#19

Re: Engine turns over perfectly but just will not crank

Alright, so checked the lead and it sparks against the ground but its like a redish orange spark with a hint of blue possibly.... I am assuming that means it is not the kill switch that is problem. from there we opened up the distributor and checked it, no water and nothing out of place..... going to pull plugs and check them for water now.....

Don S

Honorary Moderator Emeritus

Aug 9, 2011

#20

Re: Engine turns over perfectly but just will not crank

Spark sounds a bit weak. Your serial number for your engine is a number short, could you check it out?

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