Merc 700, 70hp, 2-stroke, 1977 (Belgium) Help please.

I got the motor a month ago, after a few trips I broke the driveshaft. I put a new driveshaft in and the motor was running smoth again. One day on the way home the motor did not accept any throttle and almost died at any attempt to increase speed. Well, I thought there was some scrap in the carbs. I cleaned out the carbs without changing any settings on the nozzles, a new kit for the fuelpump, all new fuellines and I joined some dryed out cables as far I could reach them.
The motor runs the same as it did before I touched it, BUT, if I take the big cover off it runns almost perfect??????
That made me think it's getting to much fuel and to little air or wise versa. I have eliminate the fuelhose quickcoupler on the motor after I heard that one can give trouble sometime. Now I don't know what to do.

Can sombody suggest something?

Kind regards
Anders / Sweden

Re: Merc 700, 70hp, 2-stroke, 1977 (Belgium) Help please.

If it runs fine with the main cover off, then there is an air blockage some where. If the main cover that you are talking about is the cover on the square air box, I would just leave it off as there is no dust nor dirt when out on the water. Older motors never had them,and they are just a noise suppressior. If you are talking about the main outer cover, I would remove the cover on the air box and put the outside cover on and see what happens. JMO
Oldman570

Re: Merc 700, 70hp, 2-stroke, 1977 (Belgium) Help please.

oldman570 said:

If it runs fine with the main cover off, then there is an air blockage some where. If the main cover that you are talking about is the cover on the square air box, I would just leave it off as there is no dust nor dirt when out on the water. Older motors never had them,and they are just a noise suppressior. If you are talking about the main outer cover, I would remove the cover on the air box and put the outside cover on and see what happens. JMO
Oldman570

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This morning the motor is not performing even without the outer "main" cover. It's like choking itself when I give throttle.
I don't think it is lack of air to the carbs but instead I think it can be an electrical problem due to it takes a few minutes before the problem comes. Maybe an dryed out cable or a faulty ignition coil. How can I meassure this things?
Anders

Re: Merc 700, 70hp, 2-stroke, 1977 (Belgium) Help please.

I think now would be a good time to buy a OME manual for that motor, as it will have testing procdures as how to test most everthing electrical on the motor. Most test will use a multimeter to do them. Manuals can be bought at most marine dealers and online at several sites.
Oldman570

Re: Merc 700, 70hp, 2-stroke, 1977 (Belgium) Help please.

I have checked the electric system and found the contact on the no.3 ignition cable very corroded. After cleaning the terminal there is no more stalling (cut-outs). Now I need to adjust the carb fuel/air. Where can I find a good site for instructions? How are the 3 cylinders sharing 2 carbs?