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1981 Mercruiser 260 stalling when shifting into forward and reverse.

B

Baron Mather

New member
The issue first happened after a couple hours of running, I was idling into the marina and the engine sputtered and died while in forward gear. The engine starts right up when in neutral without any issue. Then trying to shift into forward or reverse the engine sputters and dies out. I was able to get the boat to shift into forward gear without stalling by giving it some throttle when shifting. As long as the boat is not in gear at idle speed the engine runs perfectly fine but the second you throttle down to an idle it will sputter and die out. The issue seems to be more persistent when the engine is warm, and the boat has been running for a while.

Before the stalling issue started, I had already replaced the spark plugs, oil change, water separating fuel filter, changed out the points and the cap.
Since the issue has started, I have replaced the lower shift cable and I believe the shift interrupter switch to be in good working order. After changing the lower shift cable and doing a sea trial I have found the issue starts after the boat has been running for at least 20 minutes and the engine is warm.

The most recent sea trial I was surprised to find out that when the engine is running in neutral, and I go to raise the outdrive the engine will sputter and die out just like when I am trying to shift into forward and reverse. The engine will still start right back up in neutral in this scenario as well. This happening brings me to believe I have some sort of electrical issue going on. Currently I have the shift interrupter switch pulled for inspection and I am also in the process of replacing the ignition coil to try and rule some things out.

The carb has not been rebuilt but as far as I am aware that's not the issue. I have triple checked for corrosion on all wires and grounds for the battery and engine. I have been trying to troubleshoot this problem for a couple months now without any luck. Any insight on things I could try next would be greatly appreciated.
 
If its all original, the engine harness and the instrument panel harness are over forty years old...it could be corrosion under the insulation or something similar...a thorough inspection may be worth the effort...
 
Baron Mather said:
and doing a sea trial I have found the issue starts after the boat has been running for at least 20 minutes and the engine is warm.
Click to expand...
Ayuh,...... Sounds like the idle circuit in the carb is plugged up,.......

It idles when cold, with help from the choke,.....
 
makomark said:
If its all original, the engine harness and the instrument panel harness are over forty years old...it could be corrosion under the insulation or something similar...a thorough inspection may be worth the effort...
Click to expand...
Thankyou for the input, that is probably my next step in my electrical search.
 
bondo said:
Ayuh,...... Sounds like the idle circuit in the carb is plugged up,.......

It idles when cold, with help from the choke,.....
Click to expand...
Thanks for the response. I have had a couple people pointing me in the direction of the carb and it might just be time for a rebuild. I could be completely wrong but when the engine is warm and the problem starts happening, the engine will still start right back up and run perfectly fine in neutral. Would that still indicate something with the carb? I do not have alot of experience messing with them.
 
99% of the time when an engine stalls shifting into gear and easily restarts when put in neutral it usually means the shift interuptor switch is being made which is due to shift cable or shift linkage issues or cable adjustment issues.

You said you replaced the short cable.
Explain in DETAIL how you did this and every adjustment performed.

Lack of any specifics will not help.

Note: the interuptor switch should only engage when shifting out of gear, not into gear.
 
kghost said:
99% of the time when an engine stalls shifting into gear and easily restarts when put in neutral it usually means the shift interuptor switch is being made which is due to shift cable or shift linkage issues or cable adjustment issues.

You said you replaced the short cable.
Explain in DETAIL how you did this and every adjustment performed.

Lack of any specifics will not help.

Note: the interuptor switch should only engage when shifting out of gear, not into gear.
Click to expand...
Thankyou for the response.

The shift interrupter switch is not physically moving when im going into forward or reverse when the engine is cold or when the engine is warm and I am having the stalling issue. The switch moves as it should shifting back into neutral when I am able to to get the boat to shift without stalling. I do have the switch pulled rightnow and after testing with a multimeter it seems to be in good working order, although it does seem to be in pretty rough shape with some of the wires starting to peel and not being tight going into the switch. I am currently sourcing a new one just to rule that out. I'm not sure if once the engine is warm and the switch is getting warm if it could start working improperly.

In regards to the lower shift cable, I ordered a complete replacement kit that included the outer sleeve, the inner cable, all the shift pieces that go inside the outdrive, the gimble, along with all new pieces that attach to the shift cable and to the plate on top of the engine. I removed the outdrive to replace all this along with replacing the impeller in the lower unit. Out of water I adjusted the shift cable linkage by blocking the prop and adjusting accordingly to make sure the prop would lock evenly going into forward and reverse along with spinning freely in neutral.

Upon water trial after doing all this the boat was shifting much smoother in both directions. The engine was idling as it should and it would shift into forward along with reverse and back to neutral without any issue. Keep in mind all this was done when the engine was fairly cool and hadnt been ran long yet. With everything seemingly working correctly I decided to go for a test drive and get the boat up on plane for about 15 minutes and everything seems to be working as it should. Upon getting back to the ramp and throttling down the engine didnt stall but at idle speed I could feel the motor bogging down like it wanted to die. After shifting into forward and back to neutral a couple times positioning to get the boat back on the trailer the engine stalled on me shifting into forward. Once again it would fire right back up in neutral. (The shift interrupter physically is still not moving when the engine is stalling at this point going into gear as it should) Now in neutral with the engine running I went to raise the outdrive to get the boat back on the trailer and the engine bogged down and died just like when I was shifting into forward the moment before. Also once the stalling issue starts happening I can shift into forward and before the engine has a chance to die I can give it a very small amount of throttle and the engine will spring back to life and run perfectly fine until back at idle speed.

The outdrive has trim sensors on both sides of it that both seem to be in working order along with a hydraulic system that seems to be in working order as well. I could be completely looking at this wrong but it feels like when im shifting or running the hydraulic motor that it might possibly be pulling to much power or grounding out the engine somehow.

To me it feels the engine is losing power to the point it dies which is why im thinking its something electrical. If replacing the ignition coil and shift interrupter switch doesn't fix the issue i am unsure what direction to go next.

I am happy to try and give more detail on any aspect you might think needs more looking in to.
 
If the interuptor switch is disconnected and you still have this issue the it most likely is not your issue. is this the case? Have you tested with NO interuptor ?

Also do you have a good digital volt meter to see what the charging voltage os when running? Should be 13-14 +/- VDC

If you are not charging ans voltage drops this could be an issue.

Is your ignition a Thunderbolt IV or points? Any changes to it?
If Thunderbolt, has the coil been swapped out and if so with what type (internal or external resistor)

If its points then it has a ballast resistor wire within engine wire harness. Also any coil swapped?

What is your idle rpm when in gear?
(650-750 is spec.)

If all of the above is OK after you respond it may be a carb issue. When warm and off choke, you put in gsar and it may be going lean causing stall. Lean can be due to many reasons such as a vacuum leak...or carb idle circut or air passages or float level not being correct.
 
kghost said:
If the interuptor switch is disconnected and you still have this issue the it most likely is not your issue. is this the case? Have you tested with NO interuptor ?

Also do you have a good digital volt meter to see what the charging voltage os when running? Should be 13-14 +/- VDC

If you are not charging ans voltage drops this could be an issue.

Is your ignition a Thunderbolt IV or points? Any changes to it?
If Thunderbolt, has the coil been swapped out and if so with what type (internal or external resistor)

If its points then it has a ballast resistor wire within engine wire harness. Also any coil swapped?

What is your idle rpm when in gear?
(650-750 is spec.)

If all of the above is OK after you respond it may be a carb issue. When warm and off choke, you put in gsar and it may be going lean causing stall. Lean can be due to many reasons such as a vacuum leak...or carb idle circut or air passages or float level not being correct.
Click to expand...
I have not tried shifting with the interrupter disconnected. My plan is to do another sea trial this afternoon and once i warm the engine up and it starts stalling i can disconect the switch. Also if my understanding is correct, I shouldnt be able to shift back into neutral with the switch disconnected right?

I do have a good meter. I can test the battery while running the trim pump while the engine is on and in neutral. The battery is a couple years old and was on the boat already when i got it. Thinking about getting a new one to rule out that being a possible issues. I did check the battery with a meter while the motor was off and everything seemed to be in order with it.

The ignition is points and I replaced all the insides along with the cap after it started having the stalling issues. I also replaced all the spark plugs and set the gaps to the correct specs along with setting the timing on the motor at the start of the season before I started having the stalling problem.

I am going to swap out the current Mercury coil with a sierra one from west marine this afternoon before I do the water test. I tested the Mercury coil with a meter when i pulled it from the engine and it seemed to be in working order. Physically on the outside the Mercury coil looks like it hasnt been changed in a while. I am not sure as to what the ballast resistor wire is.

When the engine is idling correctly and not attempting to stall i believe it was pretty close to 650.

After today it might be worth me taking a look at the carb. I have already had a few people and someone on the thread suggest taking a look at it and or just going ahead and having it rebuilt. The carb is an edelbrock.

I will update after my sea trial later this afternoon.
 
Make sure coil is for point ignition and is External resister type.

A static battey should show 12.6 volts.

12 volts or less means its not fully charged

11 volts or less means dead cell (s)

Running at ~ 1000 rpm to 1500 rpm should be 13 + vokts.

Anything higher that 14.5 volts running could indicate over charging.

The ballast wire should be ok and running voltage measured at coil + should be ~ 2-3 volts less than running volts if I remember correctly.

Reinstall interuptor switch and you can connect a jumper (aligator clipped) on the ground wire. That is the wire that is screwed into mounting block that screws into bracket. The other wire from switch that screws into mounting block should have two wires and those are NOT ground. Of course the switch doesnt care which wire is connected to which terminal...

The interuptor switch when made, shorts ignition to ground and I believe on your system that is at coil. So the second wire at terminal block from wire harness at interuptor is that wire going to coil.
 
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