carb settings on 85 force

[cookiedude87]

my 85 force seemed week in one of the cylinders and was running rough at low speeds... I adjusted the carb setting on that cylinder almost all the way in maybe a quarter turn out and runs alot better... Is this bad and what may be causing this?

 

[Frank Acampora]

Re: carb settings on 85 force

YES! THIS IS VERY BAD! Do not run the engine until you have corrected it.

Anything less than 3/4 turns out from lightly seated will cause detonation and melted pistons at or near full throttle. It happens fast and most times you won't even notice it until the engine sags, loses power, or stops running.

You need to clean the carbs and then synchronize them to timing. Then set the idle mixture screws. You are NOT looking for the best idle, but the proper mixture.

All three carbs should be set the same. Start at 1- 1 1/4 turns out and adjust each equally about 1/8 turn at a time. Let the engine stabilize a few seconds before the next adjustment.

Look up carb adjustment posts for correct procedure.

 

[cookiedude87]

Re: carb settings on 85 force

So does the carbs just need to becleaned? Whydid the engine start running better when i screwed it in though?

 

[jason32038]

Re: carb settings on 85 force

A lean condition (not enough fuel to air) will cause the idle to rise.

 

[my1stboat1]

Re: carb settings on 85 force

those screws are for the idle circuit on the carbs only... If im not mistaking the carbs on the 85 hp force are downdraft carbs which have a completely different fuel circuit once operated outside idle.... I mean i could be wrong but Im pretty sure that the adjustment is just for idle mixture only .. I mean yea they shouldnt be run at 1/4 turn out theres a problem there.. but again i dont believe that circuit will cause detonation under load...

 

[Frank Acampora]

Re: carb settings on 85 force

It is possible that you have a sticking float or worn inlet needle causing that carb to go rich. It is also possible that the other two are set incorectly and you are compensating on that one carb. However, that is no excuse--It is always best to have everything set to factory specs and have it running correctly from the get-go.

As I have explained ad infinitum, a lean run will cause engine damage. Here's why: gasoline will burn within the range of 12 to 1 through 16 to 1 with optimal being at 14 to1.

The low speed circuit delivers fuel when not enough air is flowing through the venturi to siphon and vaporise fuel. The low speed circuit is ALWAYS at manifold vacuum and ALWAYS delivers fuel through the holes at the top of the carb casting right at the butterfly.

Since a venturi gets richer as airflow increases through it, the high speed jet serves to LIMIT fuel flow at full throttle. It is sized to compensate for the fuel delivered by the low speed circuit and maintain 14 to 1 ratio. THUS: If the low speed circuit is set too lean, the engine will also run lean at full throttle and detonation will occur. When it happens, it is so rapid that major damage occurs before you notice or can react.

Don't believe me? Set all your low speed needles to somewhere between 1/4 and 1/2 turn out then take the boat out for a high speed run. Your engine will last somewhere between 30 seconds to 10 minutes before it goes to lunch. Then take it to me and I will rebuild it and set everything where it should be, and relieve you of those excess Benjamin Franklins and Ulysses Grants you don't need.

 

[my1stboat1]

Re: carb settings on 85 force

hey i did say i might be wrong.. And it sounds like i am.. My carbs are set a 1 1/8 turn from lightly seated... Mine runs good... although the trim pump doesnt run at all..

 

[jason32038]

Re: carb settings on 85 force

Better a tad rich than lean. Just imagine a car engine with extremely low oil running. If the carbs are lean then the engine wont be getting enough fuel and oil and will cause extreme heat and damage.