07 mercruiser 4.3 no start

[troy lee]

run the tahoe on the hose before leaving home, run fine. got to lake will not start. if heavy throttle and key in starting position it acts like it wants to run. as soon as I let key go it just turns over. really..run fine 15 minutes later nothing. any ldeas??

 

[Scott06]

run the tahoe on the hose before leaving home, run fine. got to lake will not start. if heavy throttle and key in starting position it acts like it wants to run. as soon as I let key go it just turns over. really..run fine 15 minutes later nothing. any ldeas??

Loose battery cables or dead battery.

Man overboard switch ?

Heavy throttle - is the float bowl overflowing flooding the engine ? opening throttle wide is the way to clear a flooded engine.

 

[nola mike]

if heavy throttle and key in starting position it acts like it wants to run. as soon as I let key go it just turns over. really..run fine 15 minutes later nothing. any ldeas??

No idea what any of that means. Wants to run? just turns over?

 

[troy lee]

No idea what any of that means. Wants to run? just turns over?

key turned to start and throttle 70% it fells and acts like it going to start. when I let go of key the motor just turns over

 

[troy lee]

don

Loose battery cables or dead battery.

Man overboard switch ?

Heavy throttle - is the float bowl overflowing flooding the engine ? opening throttle wide is the way to clear a flooded engine.

t think it was flooded. I tried it again this morning and same system

 

[nola mike]

key turned to start and throttle 70% it fells and acts like it going to start. when I let go of key the motor just turns over

when you let go of the key it should either run or stop

 

[troy lee]

don

t think it was flooded. I tried it again this morning and same system

 

[troy lee]

I do not think it was flooded. I tried it again this morning and same system.
1st happened yesterday Sunday

 

[troy lee]

batteries seem good it will turn over easily just will not start..emergency switch is in normal position but yes I should check function

 

[troy lee]

when you let go of the key it should either run or stop

yes it stop no run

 

[Scott06]

yes it stop no run

Does it run when holding the key to start?

 

[troy lee]

Does it run when holding the key to start?

yes when throttled it will run with key in start position

 

[Scott06]

yes when throttled it will run with key in start position

Cycle the man overboard switch if it dies when you put key to run it’s loosing ignition this way. found that out the hard way …

when starter is running ignition is powered via starter I think, when you turn key to run if man overboard is tripped there is no longer 12 v going to positive side of coil. When cranking it will fire, as soon as key goes to run its dies. Had my man over board switch , even though though it was in run position trip out on water… got towed in by my 15 year old on jetski … no spark , screw around checking a few things , cycle switch to kill and back to run, starts right back up...

 

[troy lee]

Cycle the man overboard switch if it dies when you put key to run it’s loosing ignition this way. found that out the hard way …

when starter is running ignition is powered via starter I think, when you turn key to run if man overboard is tripped there is no longer 12 v going to positive side of coil. When cranking it will fire, as soon as key goes to run its dies. Had my man over board switch , even though though it was in run position trip out on water… got towed in by my 15 year old on jetski … no spark , screw around checking a few things , cycle switch to kill and back to run, starts right back up...

boat acts same with ovr board switch in either mode..I'm gonna bypass it and see what happens

 

[troy lee]

boat acts same with ovr board switch in either mode..I'm gonna bypass it and see what happens

bypassed switch and same issue..boat will run when key is in ignition/start position..all the way to right..let go of key and dies

 

[Scott06]

bypassed switch and same issue..boat will run when key is in ignition/start position..all the way to right..let go of key and dies

Use a VM to test

Key switch could be the issue- so are you getting 12 v out of the key switch in run? If no probably the switch. if yes, then where are you loosing it from switch to coil? On a lot of boats the 12v come from key switch and daisy chains through the gauges, and probably a fuse before it gets to the kill switch. so in run check if you have 12 v at the kill switch, if not you have two points to work backwards on where you are loosing the 12 v

 

[ESGWheel]

Not sure what type of ign / coil you have on an ’07 but here is 'how to' for the VM test Scott mentions. First you need to find the +12VDC wire at the coil. This will be what you are monitoring with the Multimeter. Take the coil wire out of the distributor and ground it in such a way it will not pop loose when cranking the engine.

Now turn the key to “Run” > do you get +12VDC? If no, issue with the upstream wiring that needs to be solved.

Now, since the engine runs with when in the key in the “Start” position, have a friend turn the key to “Start” and validate you get the +12VDC. This step ensures you were monitoring the correct terminal.

 

[troy lee]

could it be bad ignition coil. if the coil was bad would it run in start position.

 

[troy lee]

I'm going to try the test ecgwheel suggest. sure is hard for a large old man to work on this thing

 

[ESGWheel]

could it be bad ignition coil. if the coil was bad would it run in start position.

No
If runs with key in start position coil is good

Issue is voltage to coil in run

And yes sucks getting old….

:-(