1997 Mercury Force 120 - Loss of Power - Hard to Start

[L3af]

Hey Guys,

I've been having all sorts of issues with my Force.

1. There was water in my fuel. So I pumped it all out (or so I thought) and it ran good.
2. A week or so later the Motor Bogged down WOT, and I checked the fuel water separator and sure enough it was full. I was checking it periodically but it must have sucked up a lot of water in one quick go.
3. Motor obviously wouldn't start on the in board tank so I switched it to a external tank with fresh fuel and 50:1 mix. After about 10 minutes of rough idle I believe it worked all the water out and it was good to go.
4. Obviously the external tank isn't a long term solution so I drained the fuel tank again, and put fresh mix in. Fixed what I thought was the water intrusion. This worked for about a week and then the same thing happened.
5. However; this time I can't seem to get it working properly on the external tank.

Outboard was struggling to idle and had really white smoke. Eventually I got it going and had it WOT, then it bogged down and I tried to putter back to the dock. Overheat alarm went off and I turned the engine off.

What is the best plan of action trouble shooting from here?
-I put a fresh fuel filter on.
-I was planning on checking the plugs & compression, if the plugs look bad I will put new ones in.

Should I pull the carbs to clean them?
Is it possible there is an issue with the fuel pump? What's the best way to trouble shoot that on a Force?

Hoping its not something more.

 

[jerryjerry05]

To test he fuel pump: take it apart, take pics and watch the arrows when reassembling.
If it backfired at any time?? then it might have blown a gasket or 2
The port cover gaskets can pop out on the edges and suck air.
Starting Fluid test. Start the motor and spray starting fluid around the intake side, under the carbs and under the packs and around the fuel pump.
If spraying makes the motor run different?? then it's sucking air somewhere??

 

[L3af]

To test he fuel pump: take it apart, take pics and watch the arrows when reassembling.
If it backfired at any time?? then it might have blown a gasket or 2
The port cover gaskets can pop out on the edges and suck air.
Starting Fluid test. Start the motor and spray starting fluid around the intake side, under the carbs and under the packs and around the fuel pump.
If spraying makes the motor run different?? then it's sucking air somewhere??

I never heard any backfire, just a loss of power.

What am I looking for when taking the fuel pump apart?

 

[L3af]

Only had about 30 minutes to work on the motor today. Got a compression test done.

From Top to Bottom:

Cylinder 1: 135
Cylinder 2: 140
Cylinder 3: 150
Cylinder 4: 140

Seems to be within the 15% rule?

Spark plugs looked dry & dirty, I'd say they were carbon fouled but I don't have much reference, I'm new to engines.

Here are pictures of the plugs.

Cylinder 1:

Cylinder 2:

Cylinder 3:

Cylinder 4:

 

[Chris1956]

Compression is good. Spark plugs are kinda dirty, but still should work.

You should drain the carbs and see if you have water or dirt. Gas will soak into a rag, water will bead up on that rag. Use a white rag so you can see any dirt.

I think you have carb issues. Maybe you have some corrosion in the carbs from the water?

 

[Jiggz]

The first two plugs look heavily fouled up. This is an indication of carb needing adjustment (too rich) or could be that the top carb needs cleaning. You can clean the plugs but I recommend replacing them. I had good experience with NGK's BUHW. Although, others prefer the Champion L76V. Be very careful if you decide to dismount the carb and always take pic or note of small stuff orientation. Initial setting for the air screw (air-fuel screw) is 1 1/2 turn out from lightly seated. And then adjust from there but never go below 1 turn out. See the link and synch thread for proper adjustment.

 

[L3af]

The first two plugs look heavily fouled up. This is an indication of carb needing adjustment (too rich) or could be that the top carb needs cleaning. You can clean the plugs but I recommend replacing them. I had good experience with NGK's BUHW. Although, others prefer the Champion L76V. Be very careful if you decide to dismount the carb and always take pic or note of small stuff orientation. Initial setting for the air screw (air-fuel screw) is 1 1/2 turn out from lightly seated. And then adjust from there but never go below 1 turn out. See the link and synch thread for proper adjustment.

Actually ended up being an air leak! but I did adjust the air-fuel screw to get it running better.

 

[racerone]

Overheat alarm went off ?------You did replace the water pump impeller I hope.

 

[L3af]

Overheat alarm went off ?------You did replace the water pump impeller I hope.

Impeller should be fine I just replaced it and it's pissing great.

I think it overheated because it was bogging down and being started over and over.