Need electric schema of merc500 years 197x

Is anybody here have the electric schema of a mercury500 (50hp) of years 197x, don't know the exact year.
The serial number of the motor is: 7088810
Thanks a lot!

Re: Need electric schema of merc500 years 197x

1977

Re: Need electric schema of merc500 years 197x

thanks a lot!
It will help ..
Do you have the spec of the resistance of ignition coil ?
I will tell my problem ... if someone know, it would be more easy to me.
When I run the boat (in water only), at cold cold it run perfectly to full open throttle.
When it's hot (only a LITTLE hot), I can't go past 3/4 of throttle ... it missfire (don't know now if it's gas or spark .. next time i'll check)
One thing I noticed is, at all time I make it missfire, when I want to turn off the engine, it dosen't, even with the cable that goes on motor removed...
If I do not make it missfire, it turn off all the times ...
Only when I make it missfire (go through 3/4 to full), he dosn't turn off after ... I must remove the entry of gas and wait that he burn all the gas in carb. ... any ideas ?
Next time i'll go in water, i will check the spark with spark tester and the gas ... but i don't think it is the gas because I tried it at cold at full throttle and he was going in ...

Re: Need electric schema of merc500 years 197x

Your engine is a ground off engine, it works like a magneto and supplies it's on voltage to run. If it's flooding that bad you ned to make sure that it's no fuel that causing the problem, not ign. we can send a ign. test if that will help.

Re: Need electric schema of merc500 years 197x

Yes it will help.
How much fuel pressure must I have ?
I'm probably going on water tommorow, i'll check the fuel pressure.

Re: Need electric schema of merc500 years 197x

3 to 4#

Re: Need electric schema of merc500 years 197x

Hey, I missed to tell you thanks a lot!
hehe
Okay, now I went on the water and I check the spark on each cylinder (RPM) with timing light with option of RPM. (I had the multimeter too but the screen is scrap, I see better with the timing light).
I want to say that sometime the motor bug, he give some hit, at 3/4 and full and sometime he just drop off the rpm like 1000 rpm and just don't go more fast, then if I go more fast, he go and drop again or bug..
Last ride he did that, only drop the rpm, but no cylinder drop to 0 or something like that, they all drop like 1000 rpm all the time.. bug one time and the rpm was always there ... so has I see it's not the ignition the problem, true ?

Re: Need electric schema of merc500 years 197x

Oh, I didn't said that I "rebuilt" the carb, put a new kit and clean it up, but after that the problem still stay there.

Re: Need electric schema of merc500 years 197x

Sorry but I din't understand what your telling me. Here are some rules of thumb that may help. When the engine loses 1 cyl. it is a switch box, coil or the wires in between. 2 cyls not firing check the trigger for continuity 1 to 2 and 3 to 4 if they are good swap the red and red/white on the box and the blue with the /blue white if the miss goes to the other 2 cyls. the stator is bad ans if it don't change it'd the box.

Re: Need electric schema of merc500 years 197x

Sorry my english isn't perfect..
I check the RPM variation on the water, and none goes from 4000 rpm to 0 (like a bad ignition) and none has a big variation, they had the same variation when I had the problem. I followed these step from the troubleshooting sheet, it's the first step.