1984 70hp running rough...ideas??

[Freeball]

Hi guys,

I'll try and give you as much info as I can on what is happening.

1) Motor ran for around 30 mins, then bogged down and would run reluctantly at idle only. I leaned out the mixture a little and she ran well for around another hour and then had the following.

2) Would idle fine with and without being in gear ( both foward and reverse) but as soon as more power was applied it would bog down and stop unless throttles were pulled back to idle. This would happen 2-3 times before working properly however became more frequent the longer I ran it.

3) Motor started running a little rough ie. vibrating more than normal but not excessively with a very light knocking sound. I decided to call it a day here.

4) Pulled out spark plugs, they were a little wet and black (fuel too rich?) so i replaced them with factory spec. Pulled off the carbies and gave them a quick clean. There was a small amount of clear gel formed on some places.

5) Did a compression check, top cyl was 96, the other two were 105. Poured some oil into tp cyl and re-checked with no difference. Ran on the muffs and was still vibrating.

6) Put her in the water to check again and lowered the max spark advance 2 turns ( 2 deg +-) ran ok with cover off but would stall with cover on??? I decided not to push her any further until i could get her running smooth again.

I plan to overhaul the carbies and replace the fuel pump/clean the lines as obviously there is a fuel issue to address. Do I have a problem with no. 1 piston or is this within tolerence ( 10%)? Is there a problem with exhaust under the cover, I couldn't see/smell anything here? What else could be causing this engine vib, it is mounted on hard and the flywheel is secure.

I'm at a loss so any feedback/solutions are welcome.

Trying to save a few dollars

Rob

 

[tashasdaddy]

Re: 1984 70hp running rough...ideas??

OK, since you screw with all of that. 1st do you have the Factory service manual (you do not say if it is a J or E motor.)? you need it. properly clean the carbs, do mix them, they go in a certain place, do not mix up jets is each carb. http://forums.iboats.com/showthread.php?t=244013

then you need to properly reset your timing. http://forums.iboats.com/showthread.php?t=228183

then you need to do a link n sinc. (in manual for your motor)

that year had 2 different carbs, fixed jets and adjustable low speed, if you have the adjustable you have to adjust one carb at a time.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
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after you get it running, you need to do a decarb, and see if you can get your compression more even.

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[Freeball]

Re: 1984 70hp running rough...ideas??

Sorry i should have confirmed, its an evinrude. Carbs are now clean as a whistle and timing is perfect. Still have this vibration problem though....fuel and system is good. Am I looking at a piston/wrist bearing or could it be something else??

 

[Freeball]

Update: 1984 70hp running rough...ideas??

Update: 1984 70hp running rough...ideas??

Have carried out a de-carb, couldn't use seafoam is i can't find a supplier in Australia?? Spoke to a few outboard mechs and the use a product called 'ring free' for decarb. Compression is a little better in that top cyl ( now 99 approx, others are all 105). Still having vibration issues though - any advice??