How to adjust carbs on Force 120 duel carb

[Boating Newby]

The motor starts fine, idles fine, but when I give it throttle it spits and spudders like it's not getting enough gas

 

[HotTommy]

How long since it last ran right? When was the last time you cleaned the carbs?

 

[Boating Newby]

I had problems with it last summer, I winterized it and I was getting some ideas to get it fixed thus season. Carbs were cleaned out last summer. It ran great until it over heated and I had to replace the impeller and other components, since then I could not get the carbs dialed in and the throttle cable

 

[HotTommy]

If it ran well before the overheat and poorly after, it seems unlikely the carbs suddenly went out of adjustment. Overheats can be caused by more than just the impeller. For example, if the carbs were set too lean after last year's cleaning, you could get an engine that runs great until detonation causes it to damage a piston and overheat. I'd start by doing a compression check to see if the internals appear to be working right. If there is a notable difference in compression between the cylinders, I'd pull the head to take a look. ... BTW, there are specific steps to all these actions and you can do damage if you don't do them right. If you plan to do it yourself, you'd be wise to invest in a real Factory Service Manual.

 

[jerryjerry05]

Compression and spark check.
​Look in each cylinder and see if you can see any damage.
Compression should be within 5-10# of each other.
The readings with a good gauge should be about 145#
But as long as they are within 5-10# they should be ok.

Tests ok? then clean the carbs.
Get factory manual(tommy) and follow procedures for setup.

 

[Jiggz]

Since the motor overheated, a compression check on all cylinders must be done prior to checking anything else. Post your pressure readings and we can go from there.

 

[Boating Newby]

Compression test is great on all 4 cylinders
The answer I am trying to get is, on a dual carb the ajustment on the carbs does one get turned richer or leaner then the other

 

[HotTommy]

The top carb feeds the top two cylinders and the bottom carb feeds the bottom two cylinders. I see no reason to tune one leaner than the other. ... Did you see the sticky thread at the top of the forum regarding timing and carb tuning?

 

[ondarvr]

The motor starts fine, idles fine, but when I give it throttle it spits and spudders like it's not getting enough gas

When outboards don't get enough fuel they tend to smoothly slow down and possibly stop, they don't typically spit and/or spudder.

Most of the time overheating does damage someplace. And what were the compression numbers?

 

[jerryjerry05]

Even though they both operate 2 cylinders they can be set different.
​They allow the correct air/ fuel ratio at an idle.
The passages in the carbs can be different???
They need to be set while the motors warm and in the water and in gear.
They can be preset for initial start up but needs final tuning in the water.

What are the compression readings?
Just they are good isn't enough.
You can do a comp test with a finger or a gauge.
The finger will blow off with 15# and feel OK!!

Remove the carbs, clean them and check the reeds

 

[Boating Newby]

The compression in all four cylinders were 20# in 1st 22# in 2nd 21# in 3rd and 20# in 4th,

 

[Boating Newby]

Thank you for all the info.

 

[tommarvin]

You need a factory service manual, I know where to get it for a fair price.
I am going to try and send you a private message not sure how,so check your private messages,
Let me know if you get it .
Change all fuel filters?
Check fuel pump?

 

[jerryjerry05]

Compression at 20# is about 125# off??????
​The good thing is all 4 are all at 22-20#
That sounds like the gauge is weak or the test wasn't done right??

The 87-89 85hp were the only carbs that the factory suggested the air screws were to be preset at 1 turn out and left there.

 

[HotTommy]

Yep, something is amiss. The compression on my 1993 Force is typically around 150 PSI.