1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

[barefiel76]

Repairs done since last spring:
- Cleaned, rebuilt carbs.; - new plugs; - new stator; - new fuel lines; - replaced corroded wires;

Idles smoothly and sounds normal in neutral, when I shift into gear the engine stalls. Almost like it is too much pull on the engine to engage the prop under load and putters out. If I shift and advance the throttle, the engine seems to stay running, (so far that has only been tested in a barrel for a minute.)

I tried to search for other post with similar issues but was not able to find any information. Any ideas would be appreciated. Thank you.

 

[barefiel76]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

So here's an update from the lake.

Idles smoothly and sounds great in neutral, when I shift into gear the engine begins to stall. If I advance to about 1,000 RPM, engine runs in gear. After about 1,400 RPM motor begins to bog down and stalls. If I pull it back to 1,000 it will keep running. If I go back to neutral it keeps running. It sounds better in neutral than in gear. Fuel bulb remains hard.

Not sure what to do next. I have a video if that would help.

 

[Faztbullet]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

Set your idle rpm to 1200rpm in the barrel as when it in water with back pressure it will reduce down to about 900rpm. Also open the idle adjustment as suggested about 1/2 turn....

 

[barefiel76]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

I ordered a Seloc Manual w/ online access to work on this thing. Sorry, are you talking about the idles mixture screws? I have the top and bottom carb idle mixture screws about 2 turns out.

 

[gpfishingdude]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

It looks like you have done most of the things I did to my 1985 50 horse. I finally did a compression check and found that all of the cylinders had good compression. Then I checked the spark at the plug wires. You can get a cheap spark tester at auto parts that adjusts to the gap you need. I found that I wasn't getting spark at number 2 plug wire. I found out that it was just a coil by switching them around. I had to adjust the idle mixture on the carbs after I got it firing on all four. After I adjusted the mix the idle speed picked up so I had to adjust it down some. I started with the idle mix screws out about 1 1/2 turns and then adjust the top one first until it smooths out and then do the bottom one. I plan on getting the adjustments checked by a mechanic just to be sure that they are close enough that I don't damage the motor by running too lean. I have been posting what I have been doing to mine on here but nobody has made any comments so I don't know if anybody has actually read any of it. If you contact me I will try to help all that I can.

 

[barefiel76]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

I have been working on this a lot trying to figure it out. If the motor is running and I unplug the #1 or #2 spark plug the engine struggles. If I unplug the #3 or #4 plugs nothing changes. Does this mean the bottom 2 cylinders are not working?

If so what could cause that?

 

[barefiel76]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

I went to auto zone and bought a spark plug tester. Top two plugs have a bright blue strong spark, bottom two plugs have spark but it is not as strong. Looks red with dim blue to bottom two sparks.

What would have the top 2 working great and the bottom 2 struggling? Again, carbs were rebuilt, stator replaced, rotten wires replaced. I tried to use a multi meter to test ohm's for coils. Disconnected all the wires on the coils and they appear to be good.

I am left wondering if this is the result from a Trigger or fuel system symptoms.

 

[1nebel0]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

Could be the trigger..........not likely it is 2 coils as they rarely fail..Merc eat switch boxes so that is a possibility but usually just stop working...Stator can be suspect as well..You need to do tests on everything mentioned rather then throwing parts at it as you will easily drop a 700 on parts if you do the labor....don't guess.......you will need to buy or make a peak voltage adapter to be used with a digital meter to do your tests...ohm testing won't cut it........CDI has the download testing you need

 

[brnschoneck]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

do u have good compression on those cylinders ??? if so do all ur testing if not could be sumn there also

 

[barefiel76]

Re: 1984 75HP Mercury outboard, idles fine in neutral, stalls going into gear.

So I have been busy working on this frustrating boat motor. Compression test came 120 on all 4 cylinders. I used a timing light and guage to mark the fly wheel with all 4 cylinders top dead center. The timing light verified that the #3 cylinder was not firing. I just replaced the trigger with a CDI trigger. I will take for a water test today. Stator was replaced last year.

Any further ideas?

 

[Deano27]

Did you figure out the issue? Im having the same issue with my motor.

 

[MH Hawker]

a old thread

 

[GA_Boater]

Did you figure out the issue? Im having the same issue with my motor.

Start a new thread, Deano. The OP hasn't been around in over a year and a half.