Vacuum test if possible

[ferdly1]

I have a 1997 force 40 hp ELPT. I have been trying to figure out several problems my motor was experiencing, One was a sorta herky jerky feeling while I was cruisng in boat. The other was rough idle. Things I have down so far. Replaced head gasket and shaved head. Replaced foot. A neighbor of mine blew his motor up. Her gave me his old motor. I put the foot on mine, Prop shaft on mine bent and wobbled. All the electrics. Stator , regulator, both coils didn't change trigger since I changed it a few months ago. Also replaced reeds and carburetor gaskets and reed adapter plate gaskets as well as engine adpter gaskets. The engine runs better. The jerkiness seems to be gone. However still idles rough. Also seems to be worse after it warms up. I still see excess moisture on intake manifold like its sucking air. I checked by spraying wd40 around manifold no luck. Also the engine bogs down on takeoff usually a sign of carburetor problem, Carburetor cleaned and all gaskets replaced and float check for proper adjustment. I do have a question? I would like to do a vacuum test however I don't see where I could hook up my tester. Any ideas or suggestions would be appreciated.

 

[pnwboat]

Any of the fittings on the intake or carburetor adapter plate can be used to attach your vacuum gauge. You certainly have replaced quite a few things, so you've covered most of the bases. There are a couple of items that you haven't mention whether or not you've checked........have you checked the compression and replaced the fuel pump diaphragm? The moisture around the intake manifold is pretty much normal depending on outside temperature and humidity.

One other thing I wanted to mention was the carburetor. The later 1990 model carburetors have a slightly revised idle circuit in the carburetor which seems to makes it more sensitive. Typically the idle speed screw should be anywhere from 1 to 1 1/2 out from lightly seated. Depends of the motor. If it boggs down and then picks up, it may be set too lean. Turn the screw out 1/8 of a turn and try it again. Keep doing it until the bog is gone. If it boggs down and makes kind of a gurggling sound and then picks up, it may be set too rich. Turn the idle mixture screw in 1/8 of a turn and try it again.

The other thing is to make sure the idle bypass tube in the carburetor is not plugged or restricted. See item 24 in the diagram below. It's best to take the carburetor off the motor. The idle tube in the carburetor is pretty small and easily damaged if you're not careful. I would advise you not to try and remove it. To clean the idle bypass tube out, I take a piece of small stranded copper wire that is just big enough to fit inside the tube and run it in and out of the tube while twisting it kind of like a pipe cleaner. Then remove the idle mixture screw completely and take a can of carburetor cleaner with the small extension and carefully place it on the end of the idle bypass tube and give it a few blasts. Re-install the idle mixture screw and set it about 1 1/8 turn out from slightly seated. This will get you in the ball park for getting the final idle mixture adjustment.

http://www.crowleymarine.com/mercury-outboard/parts/1696_5.cfm

 

[ferdly1]

No Title

I checked the idle screw like you suggested no luck. Checked and cleaned carb again. I went to store and purchased a see thru filter to make sure I wasn't having a fuel problem. fuel looks good. I also purchased another set of plugs with an electrode, so I could get a better reading of the engine. Found something strange. Bottom plug is oil soaked top plug seems fine. Could this be caused by oil recirculation system. How do I upload a file from screencast.

 

[pnwboat]

The plugs with the electrode are not the correct type. If you run the motor under a load out on the water with those plugs, it's not uncommon for them to melt a hole through the top of the piston. Have you checked the compression? If so, what readings are you seeing?

Low speed operation can be affected by the fuel re-circulation system that is clogged. Make sure the check valves are operating properly and the fuel recirculation lines are not plugged.

 

[ferdly1]

I will put the other plugs back in. The centerfire plugs were hard to read, I went to West marine and asked for compatable plugs with an electrode. I didn't think it made a difference. With theses plugs I could clearly see a problem. Were you able to see that photo I included. If not, how do you upload a picture.. I uploaded that picture but its so small unlike the picture I took. I am getting 140 compression in both cylinders. I believe the problem is the recirculation system. I plan to check that today. Just wondering if there is a proper way to check it. up until this point I thought I had water getting into combustion chamber.

 

[pnwboat]

There's a couple of things to check.

The fuel primer solenoid #11 (choke). If it's leaking fuel into the intake, the motor will run too rich. You can test by disconnecting, pinching off or plugging the fuel supply line that is attached to the fuel bowl of the carburetor. Make sure it's mounted with a rubber grommet to help isolate it from the engine vibrations. If it seems to be stuck and leaking, you can disconnect both lines from it, take some carburetor cleaner and squirt it into the fittings while repeatedly pushing and releasing the black button on the top of it. You can also blow through it while pushing down on the black button. When you push the button down, it opens the solenoid valve and allows fuel to flow through. When you release it, that shuts it off and no fuel should flow through it.

The fuel recirculation lines themselves #3. Make sure they are not plugged. Also the one way check valves. You should only be able to suck or blow air through the line(s) connected to them in just one direction. Looks like there is one that is a t-fitting check valve #4 and I also believe that there may be one that's not shown on the diagram that is located on the block below the carburetor. If that fitting is actually located on the engine block, it should be a one way check valve. If it's located on the intake or carburetor adapter plate, it may be a regular flow through fitting. You can remove the check valve(s) and lookinto the threaded part that screws into the engine. You should be able to see the little check ball.

http://www.crowleymarine.com/mercury...rts/1696_4.cfm

 

[ferdly1]

I found my problem. I also found a connection for vacuum gauge however I didn't do a vacuum test. I did put plugs on the fittings from primer solenoid. It didn't make a difference. I was gonna hook up vacuum gauge. But as luck would have it I found air leak. One thing I decided to do was put on all new fuel lines recirculation lines etc.and see thru filter. See thru filter should be standard on boat. There was a line going from side of fuel pump to side of block. The fitting going into block was loose. Took Teflon tape tightened it up. Also changed thermostat engine was running cold-never warmed up. That explains engine running worse when warm. Didn't check carb for moisture. The engine runs good now- hopefully fuel consumption will improve-plus I feel like I gained 5mph in speed. its stlll idles a little rough. nothing like before. But I will take it. Thanks for your help guys.