Mercruiser dies after getting on temp

[YOBE]

Hi,

Did my first test run on the water today. Engine (mercruiser 165 6 inline from late 70') started fine. After driving in the water for about 10-15min (slow speed) and when the engine was on temperature it suddenly died.
After waiting for about 15-30sec I could start it again but runs for about 5 seconds and then dies again. Even if I throttle up a bit.
Thought it was missing fuel but that is not the case.
Feels like the heating up of the engine is related to this as in the first moments when it was cold it did run smooth.
Carb is cleaned.

I read that the coil could be bad. Does this make sense?
Other suggestions?

Thanks

 

[alldodge]

Very rare to be the coil

Did you do maintenance on your points, gap 16*, dwell at 31*-34*?

How old is the condenser?

 

[Scott06]

Hi,

Did my first test run on the water today. Engine (mercruiser 165 6 inline from late 70') started fine. After driving in the water for about 10-15min (slow speed) and when the engine was on temperature it suddenly died.
After waiting for about 15-30sec I could start it again but runs for about 5 seconds and then dies again. Even if I throttle up a bit.
Thought it was missing fuel but that is not the case.
Feels like the heating up of the engine is related to this as in the first moments when it was cold it did run smooth.
Carb is cleaned.

I read that the coil could be bad. Does this make sense?
Other suggestions?

Thanks

you can ohm test the coil to see if it is off spec attched is a snip from specs on an aftermarket coil for your engine Would assume yours should be close.

Also agree servicing the points and condenser is warranted, verify you have about 9 v to positive side of coil when key is in run as ballast resistor can fail. Can jumper around it briefly to test

 

[YOBE]

This is whats happening
View attachment Engine Stall.MOV

 

[kenny nunez]

Before starting the engine connect a volt meter to the +side of the coil. Set it up so that it stays connected and run the engine until it stops, the voltage should not go below 8-9 volts. If it does go down then the resistor wire is the problem. Sometimes the rotor will go to ground when the engine heats up. Try another rotor when it stops to see if it continues to run.
A non American made condenser can also cause your problem.

 

[Scott06]

This is whats happening
View attachment 410272

when it dies are you missing spark or gas ?
if you dump a little gas down carb can you keep it running ?

do you loose spark - put timing light on coil wire see if its dropping off.

On a points system there will be two paths supplying power to + side of coil- one is typically supplied off starter for full 12 v during cranking, other goes through a ballast resistor or resistor wire when key is in run and should supply 9 v when in run. Seems like you might be loosing voltage to + side of coil when in run position

 

[YOBE]

Very rare to be the coil

Did you do maintenance on your points, gap 16*, dwell at 31*-34*?

How old is the condenser?

I dont know the age of the condenser. Bought the boat second hand.
For the dwell I need to find out how I can do this.
Can this be linked to the issue I am having?

 

[YOBE]

Before starting the engine connect a volt meter to the +side of the coil. Set it up so that it stays connected and run the engine until it stops, the voltage should not go below 8-9 volts. If it does go down then the resistor wire is the problem. Sometimes the rotor will go to ground when the engine heats up. Try another rotor when it stops to see if it continues to run.
A non American made condenser can also cause your problem.

Hi, thanks for the input. But what rotor do you refer to?

 

[alldodge]

The rotor Kenny mentions is the one under the distributor cap, it's also where you will find the points and condenser

Points and condenser are cheap and a new to you boat should install a new set. Need a set of feeler gauges and watch a you tube vid for any motor to see how to do it, doesn't have to be marine

Once adjusted need to check/set timing

 

[Scott06]

Hi, thanks for the input. But what rotor do you refer to?

he is referring to the rotor inside the distributor. If it has cracks the spark energy can go to ground instead of through the cap/wires tot he plugs

 

[YOBE]

when it dies are you missing spark or gas ?
if you dump a little gas down carb can you keep it running ?

do you loose spark - put timing light on coil wire see if its dropping off.

On a points system there will be two paths supplying power to + side of coil- one is typically supplied off starter for full 12 v during cranking, other goes through a ballast resistor or resistor wire when key is in run and should supply 9 v when in run. Seems like you might be loosing voltage to + side of coil when in run position

OK, will also look into this. Keep my voltmeter connected to the + coil

 

[Scott Danforth]

I dont know the age of the condenser. Bought the boat second hand.
For the dwell I need to find out how I can do this.
Can this be linked to the issue I am having?

see post 18 and 19 in the stickies. https://forums.iboats.com/threads/must-have-technical-information-for-diyers.335378/

 

[YOBE]

The rotor Kenny mentions is the one under the distributor cap, it's also where you will find the points and condenser

Points and condenser are cheap and a new to you boat should install a new set. Need a set of feeler gauges and watch a you tube vid for any motor to see how to do it, doesn't have to be marine

Once adjusted need to check/set timing

Ok, now I got it. sorry for the questions

 

[YOBE]

I have seen online that people invest in an electronic setup. Is it worthwhile you think?

 

[Scott Danforth]

I have seen online that people invest in an electronic setup. Is it worthwhile you think?

from a cost to benefit analysis point of view..... no. a set of points lasts about 15-20 years with maintenance.

a new electronic distributor such as a delco voyager is about $400

however they do not have parts that need yearly attention like the point contacts and the rub block

 

[YOBE]

Ok, Thanks for all the input.
First data:
I did run the engine out of the water until now it does not die even after 25min. Will try more and on water.

1. when I put the key to "on" I get about 8.8V on the + of the coil. When I start the engine it briefly drops to about 6-7V. So I guess the bridge to the starter solenoid is perhaps missing or battery drop (will check, but does not relate to my issue, would be more a starting issue).
2. Ones engine runs on idle I have about 12.3V on the coil.
3. When I increase the revs to about 2500rpm + coil gets about 12.8V close to 13V

But I suppose this is because of the alternator doing its job and increasing the voltage. Directly on the + of the starter I have about 14V.

Or is the 12.6V volt on the coil during operation too high??
Will need to find out what the is cause of that then....

The feeler gauge is ordered so I can double check the points. But when I opened the distributor it looked quite decent. But will check more.

Regards,

 

[Scott Danforth]

something not right. should be ~8-9 volts when engine running at the coil, and battery voltage when cranking

make sure to get a points file (or use one of your wifes emery boards) and a dwell meter along with the feeler gauges. the points file is to dress the contacts, the feeler gauges are for rough gapping, the dwell meter is to precisely set the points.

 

[redneck joe]

Scott and others are the smart ones but I had a 79 with very questionable history and had been in a barn for 6 years. Mine was acting and sounding similar. After much talking here I paid someone to look at it and determined that the plug wires and such appeared to be original. Replaced all those never had that problem again. I did put in electronic ignition afterwards.

 

[YOBE]

I fixed the issue of the dropping voltage when cranking. For some reason the wire between the Positive Coil and the "R" on the starter motor was missing.
Now when starting the engine I get "battery voltage" on the coil.

The "resitor wire" is still unlcear. Something is not right. They seemed to have made some bridging somewhere...

 

[YOBE]

something not right. should be ~8-9 volts when engine running at the coil, and battery voltage when cranking

make sure to get a points file (or use one of your wifes emery boards) and a dwell meter along with the feeler gauges. the points file is to dress the contacts, the feeler gauges are for rough gapping, the dwell meter is to precisely set the points.

OK, so even during runing of the engine when alternator kick's in it should be still around 8-9Volts! I need to find this voltage drop I have somewhere and what it is