Adjusting idle on 85 hp force

[kthkollar]

I was wondering if anyone had some good info on adjusting the idle on an a 1986 force 85 hp. Thanks everyone!

 

[sho3boater]

Re: Adjusting idle on 85 hp force

The idle is set with the timing arm like many older outboards. I got mine around the right speed, then in gear on the lake I set all the idle mix jets low as I could without it dying, one at a time. I then opened them just a hair, and set the idle to where it would just stay running when put in gear at a stop. Then turned idle up just a hair. It has been fine that way. The Mercs I have run had to be set differently, more rich at idle, and they would change with the weather (get more rich hotter weather). These stink so much I set it lean as I could, but it does not appear to care the Mercs would die out at times and this does not. Mine is an '83 I assume it is the same with the three carbs. I cleaned them first and put new plugs in.

Most all these old OB I have seen the idle is in the carb and you can't change it. They retard the timing to idle it down that keeps a smooth idle and airflow in the motor. When you see the timing arm stop and throttle starts to open (about at a faster trolling speed), that is actually idling on the carbs, lower rpm than that is wasting fuel with a under timed motor. But that is the way they idle slow the best.

 

[Dave K.]

Re: Adjusting idle on 85 hp force

Factory spec on my '84, 85hp is 7/8ths out from lightly seated. Do not go any further out. Plenty of info from a "search" on this & I've read where 3/4 out is good too.

 

[ezez]

Re: Adjusting idle on 85 hp force

Factory spec on my '84, 85hp is 7/8ths out from lightly seated. Do not go any further out. Plenty of info from a "search" on this & I've read where 3/4 out is good too.

There is a lot of info. if you search. DK's post has really nothing to do with the OP question as he is talking about the mixture screws and not the idle speed adjustment. In addition, his post SHOULD say that you need to adjust the mixture AT LEAST 3/4 to 7/8 of a turn OUT from lightly seated. Anything less than that and run the risk of running lean and doing engine damage.

The idle speed adjustment is made on the tower shaft which adjusts the timing advance.

 

[john from md]

Re: Adjusting idle on 85 hp force

Idle speed depends on several factors.

Pre start

1. The throttle cable length must be adjusted first.
2. The throttle plates need to be set evenlly.
3. The idle/timing linkage must be adjusted with the link rod.
4. The eccentric on the carb pick up must be adjusted to the trottle cam.

Post start

1. The idle must be adjusted to 750 rpm with the trottle in gear and the boat tied to the dock.
2. The idle mixture screws must be adjusted to get best rpm while in gear at dock. Do not turn in further than 7/8 of a turn out. 1 turn out is safer.

This assumes that your timing is set correctly.


Buy a book, it tells you how to do this and more.

John