1987 85HP Force Running Rough and Backfiring

[anewlife1]

Ok so here is a situation that is making me go nuts! I have a 1987 85 HP Force outboard. We rebuilt all three carbs recently as they were gummy and sticky and stuff. We put them back on and it did this before the carb rebuild as well but when you go to start it the engine will spit and shut off. Sometimes it won't start hardly at all. When it does start, it constantly spits and sputters and just runs really rough. We adjusted the carbs as much as we could. It seems to be running really lean. If we close off the choke it runs better and if we hold our hand over the carbs or carb it runs better.

If I remember right, the compression was like 125/120/115 or something like that. I know there was less than 10 lbs difference between cylinders. I would really appreciate any help I can get.

 

[jerryjerry05]

Re: 1987 85HP Force Running Rough and Backfiring

Remove the carbs and check the reeds.
Do another comp test.
Check the wiring diagram,make sure the leads are connected right.
Check the fuel pump diaphram and for water in the gas.

 

[anewlife1]

Re: 1987 85HP Force Running Rough and Backfiring

Thank Jerry Jerry we will work on that this afternoon and post our results. I appreciate your advice

 

[anewlife1]

Re: 1987 85HP Force Running Rough and Backfiring

Ok new update on this issue. I think I am in need of a brain surgeon.

Checked the Compression and got 124 on #1, 125 on #2 and 124 on #3. We did it three times on each cylinder and it came close to these numbers everytime.

We checked the wiring per the diagram in the manual and everything was hooked up correctly.

We took off the carbs and got into the reeds and we really don't know if we could see daylight or not as the sun was down, but if we held a flashlight up to them we could see some light coming thru a few of them. Now if we held it up to a flourescent light in the garage we couldn't see anything.

We really don't know what the function of the reeds are. I guess my question is if they are bad, will it cause a vacuum leak in the engine? I ask this because when the boat would run, if we held our hand up to the carb, it would run a whole lot better. I guess, maybe a better question, will it make the engine run leaner if the reeds are bad. We are kinda at a loss as to what to do next. Please if anybody can help I would really appreciate it.

Brian

 

[Jiggz]

Re: 1987 85HP Force Running Rough and Backfiring

When you put your hands over the carbs or carb, you are basically enriching the fuel air mixture. Thus, to me it seems you need to adjust the fuel-air screw or what others call air-screw. This is the screw with a spring on it on the each carb. Start with each one by turning it clockwise (CW) slowly until lightly seated. Do not force or you will damage the needle. From lightly seated, loosen it up by turning counter clockwise (CCW) a full turn and a quarter or 1 1/4 turn from lightly seated. Do the same for the remaining carbs.

If the idle doesn't improve, you need to adjust the idle screw which is located on the bottom of the control tower shaft. Rotate this CW one full turn until you get the engine to idle. Smoothen the idle by adjusting the air screw again going CW a little bit at a time (1/8 turn at a time) until you are only about 1 full turn from lightly seated. and then set the idle speed around 1000~1100 RPM on muffs in neutral or 700~800 RPM in gear in water.

If after setting the initial air screw settings and the engine will still not idle, you might need to clean the carbs. I use brake cleaner although others use carb cleaners or something very special. You can do this by totally removing each air screw and shooting cleaning agent into it.