1996 Force 40 outboard

[jamesandhollie6865@gmail.]

I have a 1996 force 40 outboard 2 stroke. It has a rough idle. I have rebuilt the carburetor, new plugs , coils, fuel pump and fuel lines with filters. All of these are OE parts. I made sure the throttle plate was horizontal at full throttle. It runs good at 1/4 to 3/4 throttle. At full throttle it has a skip and feels under powered. Could this be timing or idle air screw out of adjustment. Any help would be great.

 

[Jiggz]

You might want to check for compression first to make sure you are firing on all cylinders. Post the results in here.

 

[jamesandhollie6865@gmail.]

I just checked the compression and there is 120 psi on each cylinder.

 

[jamesandhollie6865@gmail.]

You might want to check for compression first to make sure you are firing on all cylinders. Post the results in here.

120 psi on each cylinder

 

[Jiggz]

120 psi on each cylinder

Great. Now you have to isolate if the miss is fuel related or spark (electrical related). The best and easiest way is to do a cylinder drop test. This involves pulling the spark plug cable off while the engine is idling. You will have to do it quick to make sure you do not destroy the cd mods. Use insulated gloves to prevent shock. If the engine dies when you pull a plug wire that means, that cylinder is the only cylinder firing and the other one is not. However, if the engine continue to run with NO change in engine rpm, it means that cylinder is NOT FIRING at all. First, check for sparks on this particular cylinder. If there is sparks, then the next move will be to make sure the reeds are still good. It is really hard to tell if reeds are good or bad without physically looking at it.

You mentioned you installed in-line fuel filter after the fuel pump and before the carb. Is it a clear type? Is it at least maintaining 1/2-3/4 full when engine is running? How about when you go full throttle? You can try this in the lake or water with the cowling off, but you need a second person to run the boat for you. If the fuel filter runs low on gas at full throttle, it could be a bad primer bulb or fuel pump diaphragm is torn.

 

[jamesandhollie6865@gmail.]

Great. Now you have to isolate if the miss is fuel related or spark (electrical related). The best and easiest way is to do a cylinder drop test. This involves pulling the spark plug cable off while the engine is idling. You will have to do it quick to make sure you do not destroy the cd mods. Use insulated gloves to prevent shock. If the engine dies when you pull a plug wire that means, that cylinder is the only cylinder firing and the other one is not. However, if the engine continue to run with NO change in engine rpm, it means that cylinder is NOT FIRING at all. First, check for sparks on this particular cylinder. If there is sparks, then the next move will be to make sure the reeds are still good. It is really hard to tell if reeds are good or bad without physically looking at it.

You mentioned you installed in-line fuel filter after the fuel pump and before the carb. Is it a clear type? Is it at least maintaining 1/2-3/4 full when engine is running? How about when you go full throttle? You can try this in the lake or water with the cowling off, but you need a second person to run the boat for you. If the fuel filter runs low on gas at full throttle, it could be a bad primer bulb or fuel pump diaphragm is t

 

[jamesandhollie6865@gmail.]

I did a cylinder drop test a few weeks ago and noticed the engine would run on #1 cylinder alone but not on #2 cylinder alone that's when I put new coils on it. I did put in new reeds too. I have a new filter before the prime bubble and a small white filter before the fuel pump but not one after the fuel pump. The filter before primer is staying 3/4 full at full throttle but I haven't checked the one before the pump. With it being white I probably wouldn't be able to tell so I will change that out as well

 

[jamesandhollie6865@gmail.]

I did a cylinder drop test a few weeks ago and noticed the engine would run on #1 cylinder alone but not on #2 cylinder alone that's when I put new coils on it. I did put in new reeds too. I have a new filter before the prime bubble and a small white filter before the fuel pump but not one after the fuel pump. The filter before primer is staying 3/4 full at full throttle but I haven't checked the one before the pump. With it being white I probably wouldn't be able to tell so I will change that out as well

Where should the idle air screw be as far as adjustment???

 

[jerryjerry05]

The "idle" air screw is for running at idle, usually has no effect on running at high speeds.
Set the screw at 1. 1/2 turns out. Then in the water, in gear, turn the screw in 1/8th turn then wait 10-12 seconds (that burns the fuel at the old setting) then again 1/8th turn until the motor smooths out.
If it won't work??? Then it might be sucking air?
Do the starting fluid test.

 

[jamesandhollie6865@gmail.]

The "idle" air screw is for running at idle, usually has no effect on running at high speeds.
Set the screw at 1. 1/2 turns out. Then in the water, in gear, turn the screw in 1/8th turn then wait 10-12 seconds (that burns the fuel at the old setting) then again 1/8th turn until the motor smooths out.
If it won't work??? Then it might be sucking air?
Do the starting fluid test.

Thank you. Will give that a try

 

[Jiggz]

I did a cylinder drop test a few weeks ago and noticed the engine would run on #1 cylinder alone but not on #2 cylinder alone that's when I put new coils on it. I did put in new reeds too. I have a new filter before the prime bubble and a small white filter before the fuel pump but not one after the fuel pump. The filter before primer is staying 3/4 full at full throttle but I haven't checked the one before the pump. With it being white I probably wouldn't be able to tell so I will change that out as well

There is already a small stainless screen filter just before the fuel pump. No need for another fuel filter, instead of replacing the white one, replace with clear one and move it after the pump just before the carbs. This will be a good troubleshooting tool for fuel related problems.
As for the idle mixture screw, as mentioned initially set it to 1 1/2 turns. While idling, screw it in 1/8 of a turn and wait for a few seconds for the engine to settle down. Continue to screw it in until the rpm starts to increase due to a lean mixture. Then start going the other way around, i.e. screw out (counter clockwise and count the number of 1/8 turns) until the rpm starts to decrease due to rich fuel mixture. The recommended setting is in between the lean and rich mixture settings, i.e. 1/2 of the number of 1/8 turns you made from lean setting to rich setting. Personally, I would set it just a tad or 1/8 of a turn more from mid settings to ensure proper lubrication at idle. A little lean setting is more harmful than a little rich setting.
After setting the idle mixture screw, set the idle setting using the idle screw at the bottom of the timing tower. And it should be around 1000 rpm on muffs in neutral and idle. No need to disengage linkage from the timing tower, just loosen the 7/16 nut on the idle screw and screw it in or out to increase or decrease rpm. And then re-tighten the nut.

 

[jamesandhollie6865@gmail.]

There is already a small stainless screen filter just before the fuel pump. No need for another fuel filter, instead of replacing the white one, replace with clear one and move it after the pump just before the carbs. This will be a good troubleshooting tool for fuel related problems.
As for the idle mixture screw, as mentioned initially set it to 1 1/2 turns. While idling, screw it in 1/8 of a turn and wait for a few seconds for the engine to settle down. Continue to screw it in until the rpm starts to increase due to a lean mixture. Then start going the other way around, i.e. screw out (counter clockwise and count the number of 1/8 turns) until the rpm starts to decrease due to rich fuel mixture. The recommended setting is in between the lean and rich mixture settings, i.e. 1/2 of the number of 1/8 turns you made from lean setting to rich setting. Personally, I would set it just a tad or 1/8 of a turn more from mid settings to ensure proper lubrication at idle. A little lean setting is more harmful than a little rich setting.
After setting the idle mixture screw, set the idle setting using the idle screw at the bottom of the timing tower. And it should be around 1000 rpm on muffs in neutral and idle. No need to disengage linkage from the timing tower, just loosen the 7/16 nut on the idle screw and screw it in or out to increase or decrease rpm. And then re-tighten the nut.

Thank you so much for the information it's greatly appreciated. Will do that you have mentioned and will respond to let you know how it goes. It may take a day or so.

 

[jamesandhollie6865@gmail.]

Thank you so much for the information it's greatly appreciated. Will do that you have mentioned and will respond to let you know how it goes. It may take a day or so.

I checked the timing with an induction timing light and time is 9° restarted. I've been trying to set timing at zero at idle and man there are two many adjustment rods on this engine. If I take all adjustment rods looses and get timing set, then adjust rods and throttle linkage to that will that work like I'm thinking

 

[Nordin]

You never set the timing on these engines at idle.
You set it at WOT and it should be about 30 dgr BTDC.
The setting depends what fuel you are using.
It is better to retard it some degrees then advance it.
I usually set the timing to 28 dgr static (throttle at WOT and turning the engine over with the starter).

 

[jamesandhollie6865@gmail.]

You never set the timing on these engines at idle.
You set it at WOT and it should be about 30 dgr BTDC.
The setting depends what fuel you are using.
It is better to retard it some degrees then advance it.
I usually set the timing to 28 dgr static (throttle at WOT and turning the engine over with the starter).

When you say static is that with plugs out wide open throttle or leave plugs in and take coil wire off and attach timing light leed to #1 coil. I'm using 87 octane.

 

[Nordin]

You can do the static both ways.
I do it with the plugs in, if you do it with the plugs out you have to ground all plugs cause you can damage the CD box (switch box).
Okey you run 87 octane. I am in Sweden and the lowest octane we have is 95.
I would suggest you to retard the timing to 28-30 dgr BTDC at WOT.
Lower octane, retard timing.
The fuel was better in those days these engines was made and the factory spec. for the timing is 32 dgr BTDC.

 

[jamesandhollie6865@gmail.]

Thank you so much.