70 yamaha loses power

[FUNCAT-YAMAHA]

I hope someone can help!

I have a '84 Yamaha outboard.
It starts fine and runs out from my dock through the no wake fine.
When I take off it runs fine for about 5 minutes and then loses power.
I am not sire if it is overheating and the electronics are holding it to a 1500 rpm max or I lose a cylinder or something.
I have another motor on an identical boat and ave swapped a few parts back and forth without any change.
I have pumped the primer bulb when running and nothing changes.
I have swapped the coils and the CDI box.
The compression is 105, 95 and 95 in the cylinders when cold and slightly lower when hot.
The motor sat for several years before I bought it.

I hope someone can help. Please respond with suggestions or more info.

Thanks

 

[rodbolt]

Re: 70 yamaha loses power

can you post the model number ?

 

[FUNCAT-YAMAHA]

Re: 70 yamaha loses power

It will be a while to post that as the boat is not at my house.
It is a 3cyl. 1984 and I believe the same through 87.

 

[J00ky123]

Re: 70 yamaha loses power

check the easy stuff
- first check the warning buzzer to see if that works.
- Make sure your battery connections are very clean and super tight.

 

[Ray Neudecker]

Re: 70 yamaha loses power

Take a timimg light with you and check the fire when it acts up. The 3 cylinder CDI's do fail and they do it intermittently.