1981 260 mercruiser

[kfx400]

Newby here,
I have encountered this problem over the last 2 summers trying to resolve with replacing parts,
Fuel system- have replaced with new fuel line,fuel pump,filters and new carb.
Ignition system-Have replaced battery,plugs,wires,coil and electronic ignition,cap and rotor.

Problem- After 20 to 30 minutes of cruising the boat starts to to act like its not hitting on all cylinders, it will eventually just not keep itself on plain. it will idle and rev fine when not under a load, but will not pull it self back to plain unless it has cooled down for several hours, then it will run fine again for 10 to 20 more minutes and act up again, Seems to me it is a heat related issue.

I'm beginning to wonder if I'm getting some voltage loss from the coil to the distributor!
Please Help,I'm at my wits end and about ready to sink it!

 

[chiefalen]

The shift cutout switch sitting in the v or slipping and engaging maybe. cuts half the cyl when engaged.

So when it happens have someone else drive and look at it if you adjust it and the problem goes away you found your problem. Or you can disconnect it under way on the water. Maybe thats your problem i'm surprised no one told you to check it.

 

[kfx400]

The shift cutout switch sitting in the v or slipping and engaging maybe. cuts half the cyl when engaged.

So when it happens have someone else drive and look at it if you adjust it and the problem goes away you found your problem. Or you can disconnect it under way on the water. Maybe thats your problem i'm surprised no one told you to check it.

Where exactly is this located on the motor?
Pics would help,thanks for replying!

 

[chiefalen]

Shift converter on the top of the motor, have someone shift the throttle you look at the moving parts see a microswitch that gets engaged for a split second. Thats the switch, it could be located in a bunch of different places the converter on the motor.

You could put water to the drive if on a trailer start the motor, after you find the switch and press in the button see if it affects the motor, should cut half the cylinders out.

Should only work in the water comming out of gear.

 

[kfx400]

Shift converter on the top of the motor, have someone shift the throttle you look at the moving parts see a microswitch that gets engaged for a split second. Thats the switch, it could be located in a bunch of different places the converter on the motor.

You could put water to the drive if on a trailer start the motor, after you find the switch and press in the button see if it affects the motor, should cut half the cylinders out.

Should only work in the water comming out of gear.

Ok I'm on board, I know what your talking about and yes I will check it for being loose, I know that the micro switch in fact works like it is supposed to but I will double check to make sure it is secure, I'd almost bet my last dollar that it is fine but great advice,Keep giving me ideas!

 

[kfx400]

Ok I'm on board, I know what your talking about and yes I will check it for being loose, I know that the micro switch in fact works like it is supposed to but I will double check to make sure it is secure, I'd almost bet my last dollar that it is fine but great advice,Keep giving me ideas!

Newby here,
I have encountered this problem over the last 2 summers trying to resolve with replacing parts,
Fuel system- have replaced with new fuel line,fuel pump,filters and new carb.
Ignition system-Have replaced battery,plugs,wires,coil and electronic ignition,cap and rotor.

Problem- After 20 to 30 minutes of cruising the boat starts to to act like its not hitting on all cylinders, it will eventually just not keep itself on plain. it will idle and rev fine when not under a load, but will not pull it self back to plain unless it has cooled down for several hours, then it will run fine again for 10 to 20 more minutes and act up again, Seems to me it is a heat related issue.

I'm beginning to wonder if I'm getting some voltage loss from the coil to the distributor!
Please Help,I'm at my wits end and about ready to sink it!

I've been doing some searching but am not sure what I need for the stock distributor.
Anyone know what ignition module I need. (Link would be helpful)
Since I have replaced everything A good mechanic I know told me it has to be the old module is getting hot and breaking down.

 

[kfx400]

Newby here,
I have encountered this problem over the last 2 summers trying to resolve with replacing parts,
Fuel system- have replaced with new fuel line,fuel pump,filters and new carb.
Ignition system-Have replaced battery,plugs,wires,coil and electronic ignition,cap and rotor.

Problem- After 20 to 30 minutes of cruising the boat starts to to act like its not hitting on all cylinders, it will eventually just not keep itself on plain. it will idle and rev fine when not under a load, but will not pull it self back to plain unless it has cooled down for several hours, then it will run fine again for 10 to 20 more minutes and act up again, Seems to me it is a heat related issue.

I'm beginning to wonder if I'm getting some voltage loss from the coil to the distributor!
Please Help,I'm at my wits end and about ready to sink it!

Found my problem,
It was a low voltage issue to the coil with the electronic ignition.The module operating range is between 8 and 14 volts.
My voltage was dropping below the minimum and causing the igniter to start shutting down. I've got a dirty connection in the wiring harness somewhere and the heat in the motor compartment was causing the voltage loss to the coil.
Easy fix.I just bypassed the wire harness and ran a new wire from the ignition switch 12v to the positive side of the coil.
Wala, It runs like a champ!

 

[chiefalen]

i did something a little different on my boat. I installed a switch at the helm give power straight to the coil from the battery. Switch on start boat turn key off still runs switch off boat off.

Just like the old style cars.