I have a friend with a new to him Force 125 that doesn't like to idle or go at slow speed...with the cowling on. Take it off and it runs as it should. Where should I point him for troubleshooting?
The rubber accordion exhaust boot on the two exhaust relief holes that come out of the back of the upper portion of the lower unit. If it's leaking, exhaust fumes will fill up the inside of the cowl and affect the way the motor runs.
The clamp holding the bellows can rot away and the bellows leak..
I had to replace both of mine with SS clamps.
Also the gasket between the powerhead and spacer plate can go and fill the cowl with exhaust.
Depending on how bad?? you can fill the hole with silicone and maybe stop the leak.
I had this problem on one of my motors and filled it and it's worked for 4 years.