1991 force 120 starting/idling issues

[Bkedds]

Was recently gifted a 1991 bayliner capri with a 120 force outboard. I was told that the previous owner had spent thousands trying to get the boat running and were unsuccessful. The last time is was running was 3 years ago. I was told they had done a compression test when they were attempting to fix it and that compression was fine.

I have been working on it for the last week and have changed the plugs, fuel filter, new starter, new battery, new impeller.

The gas that was in the tank was 3 years old so I siphoned the tank and put in fresh gas.

After doing these replacements I have been able to start it but it runs rough. Will only idle on the fast idle setting and dies when I put it in neutral.

I took the boat out on the lake today and after many attempts was able to get it in gear without stalling. At full throttle the boat does not miss or cough and runs relatively smooth. The issue is that at full throttle i was clearly not getting full power. At best I was able to get up to 10 mph with the throttle wide open and was not even able to get on plane. I ran the boat for about an hour wide open and there was no fluctuations in speed. The tach on the boat isnt working so I couldn't tell how many rpms I just know by the sound that it is not even close to where it should be at full throttle.

My hunch is that there may be 2 separate issues here. I'm thinking about pulling the carbs and cleaning/ rebuilding which may help with the idle issue. As far as not getting full power at full throttle maybe the fuel lines have an air leak ?

Any suggestions would be greatly appreciated.

 

[jerryjerry05]

Model? Serial?
First do a compression test and a spark check on each cyl.
Setting that long?? the fuel pump probably needs a rebuild.
The carbs probably need a cleaning.

Post the results?

 

[Bkedds]

Model 1201x91h
serial 024117

Did the compression test this morning.
120, 130, 130, 130.

bought an in line spark tester. All 4 plugs are firing.

 

[Bkedds]

Just took the carbs out and cleaned them. They were in pretty good shape. I also noticed that the butterfly valves weren't opening and closing in the same position so I adjusted the arm so they do. After doing that and turning up the idle it starts ok now. Going to take it out tonight on the water to see if it has more power. Could the valves not being aligned cause any of these issues?

 

[Bkedds]

Little update. Turned the idle way up and now I'm able to start the motor every time no issue. I'm out on the water right now and having some strange issues. The boat idles at high rpms (not sure how many because tach isnt working) but when in gear and even full throttle you can hear the rpms drop and the boat is only able to do 7mph.

Any feedback would be really appreciated.

 

[roscoe]

How are you adjust idle up?
What are you adjusting?

Did you properly set carbs and sync them,

don't run it if the carbs may be running lean

""I ran the boat for about an hour wide open""

Wide open, 7 mph, something is wrong.
Running a damaged or ill tuned engine will only cause more damage.

If you have compression, and spark, then it is fuel.

If one or more cylinders is not getting fuel, then it is not getting lubrication either.

How do the sparkplugs look?

 

[Bkedds]

I adjusted the idle with the idle stop screw on the side of the motor. It is idling quite high now. Spark plugs are new but when I pulled them for compression test this morning 2 of them were dirty looking. When I was on the lake today it idled high and when I put it in gear it dropped. At full throttle it has less power than at high idle. As soon as I popped it back into neutral it began idling higher than it was in gear.

 

[The Force power]

In addition to roscoe advice;

Get a tiny tach to verify the RPM's
Verify if its running on all cylinders by pulling cable off plug & check for rpm-drop
Have you read the sticky-notes on the top of this forum?

 

[jerryjerry05]

When you cleaned the carbs?? did you run a tip cleaner through the jets?

Does the squeeze ball pump up firm? Yes? that's good.
No then the pump needs a rebuild. Or an inline connectors sucking air?

Do the starting fluid test: start the motor, spray SF around the intake side of the motor,
under the packs and coils and around the port covers and fuel pump.
If that makes the motor run different? then it's sucking air someplace??

 

[Bkedds]

I will pull the carbs again today and run a tip cleaner through the jets. When I cleaned them previously I only used air. I will also try to get a tach that works so I can check the rpms and i will attempt the starting fluid trick. I am going to set and sync the carbs as per the sticky in this forum and I will post results once I get out on the lake tonight.

 

[Bkedds]

Just noticed that the yellow wires coming from the stator are burnt at bit. Could this have anything to do with my issues?

 

[The Force power]

Just noticed that the yellow wires coming from the stator are burnt at bit. Could this have anything to do with my issues?

The yellow-wires are for the rectifier to charge the battery, maybe the Stator has more issues

 

[Bkedds]

I just had a thought. Since I've been working on the boat daily and taking off the carbs frequently and tinkering, I have left the air boxes off of the carbs. And if i remember correctly, both times I had the boat out this week I was running it without the air boxes. Would this cause the motor to run lean and result in loss of power at full throttle like I've been experiencing?

 

[roscoe]

no, the air boxes do not affect the carb operation

many motors are running without the boxes

 

[jerryjerry05]

Is the foam still in the cowl?
Sometimes the foam falls down and shuts off the air?

Does it run better without the cowl?

 

[Bkedds]

It runs the same with or without the cowl. The foam is still attached. I've read many posts about running with the air silencer box off being a possible culprit for low power. I did a carb set and sync and installed the air boxes. I'm going to take it out today and see if I can get it running properly. If it still doesnt get up to speed with full throttle I will be stumped.

 

[Bkedds]

Well I finally figured it out. I took it on the lake today and it was the same problem. Idled ok but no power in gear. It sounded to me like it wasnt firing on all cylinders. So I began pulling plug leads and realized that when I pulled the third one it made no difference to the rpms. So I swapped the third and fourth lead around and boom. It got full power and got on plane no problem. Now it starts each time, idles perfectly and goes like stink. Thank you to everyone who helped me with suggestions and tips. Even though Its embarrassing that it was such a simple fix I'm glad i took the time to do all the small things that need to be done on outboards so I could learn how to keep it running well.

 

[jerryjerry05]

Of all the things we try to diagnose.
The crossed wire might be the hardest???

MY question for you?? What took so long to notice a plug wire ?????