Mercury OB Won't idle in water

[fire513]

I have a 1979 merc. ob 70hp. At home with the water muffs on it will idle great. When I put it in the water I can't get it to idle. The motor starts great at both places and runs great when it's in gear on the water.

 

[hondon]

Re: Mercury OB Won't idle in water

Any time you have problems in this area ,you'll need to start with the basics.What are your compression readings?Have you done the sync and link, which means timing this thing carb to ignition.That can be tricky and impossible without a manual.An engine out of sync will idle like crap,or not reach WOT ,or etc.etc.

 

[jmvaughn]

Re: Mercury OB Won't idle in water

fire513,<br /><br />How is it going.<br /><br />My experience with these older ccarb. motors that idle fine in the yard with the muffs on them and then won't idle well in the water is simple. Idle the motor up while on the muffs in the yard. In the yard the motor has no back pressure on the motor exhaust. A motor that idles fine on the muffs at 700 RPMs or so will lose a few hundred RPMs when it is in the water due to this back pressure. So now your not getting 700 RPMs your getting 400 RPMS or so. If your motor is already running near 1200 RPMs while idling on the muffs then this might not work for you. But, it just might help.