merc 470, still having issues

[jo8330]

Howdy I have a 1980 merc 470. I know its an art form to try and get these things to run properly, so here goes. Just got a hold of this boat (1980 baretta cuddy cabin) and was told the motor runs good. Ok well, I figured it wasnt gonna fire right up, but I tried anyway. Well it needed a starter, so I fixed that. Then it needed a coil. Fixed that. Now im at this point. Dumping fuel into the carb, the motor sputters and pops, then shoots a flame out of the carb but definitely wamts to fore. I have gotten it to stay running for about 15 seconds. ...oh but itbhas burned out two coils now. So far I have replaced points, cap, rotor, wires, plugs coil, and I just did the fuel pump so I dont have to pour gas down the carb lol. Im at a loss. I am going to check the resistance wire, the leads from the ign to the coil, but they all look new Also if im to replace the purple resistance wire, what do I have to use to do so ? One more thing, I have a wire coming out.of the distributior that goes from the points, to the hot side of the coil. I cant find this on any diagram out there. Is this a jumper wire of some sort ? Could this be why Im burning out coils ? Im not sure how the previous owner rigged this thing, but he was a master of redneck mechanics (no offense to anyone) so im sure theres probably a few things that shouldnt be. How hard would it be to rewire the whole ignition circuit ? Considering it. Electrical isnt mg strongest suit and I hate tracking down the demons... Im good with a volt meter though.

 

[Bt Doctur]

coils don't burn out that fast. the wire coming from the dist goes to the negative side of the coil. 12v power goes thru resistance wire or a ballast resistor then to the positive side of the coil.
You need to set the point gap to around .018 or a paper match book., then check /adjust the timing .make sure the old fuel coming out of the tank is really fuel and not fuel mixed with water.

 

[jo8330]

Thanks. Is there a way I can use an external resistor instead of the wire ? Or if I re run a wire, what males that particular wire special ? What kind of wire do I have to get ? what kind of voltage should I be getting with the key on at the coil ?

 

[glenn property of pam]

you have replaced the coil with a original or a different type.
There are 2 types of coils, one is a internal resistor which does not require the external resistor wire. The other is a external resistor that does require the external resistor wire. Either way it shouldn't toast a coil in a that short of a time. check which coil you are buying.
I have included a link that's to a different merc but basic engine design of the ignition wiring is roughly the same which shows how the coil is wired.
http://www.boatfix.com/merc/Servmanl/13/13E4R2.PDF

 

[nola mike]

Did you measure the resistance of the wire? Didnt see a mention of replacing the condensor? How old is the fuel? Did you check/clean your fuel filters?

 

[jo8330]

Hi guys. Replaced condensor also. Forgot to mention that. No I didnt measure that yet. Havent had a chance. Did all the basic tune up stuff first in hopes it would start. How do I measure it ? Also, pumped out as much old fuel as I could through the fuel sender area, added 5 gallons of fresh premium....cleaned out the water seperator also. The coil I replaced it with says it requires an external resitor (which I was assuming was the reisitor wire) ...and I believe its made by standard. The only thing I havent checked /cleaned is the fittng on the fuel tank. But we tried running it off a seperate tank and that didnt do it either. Accelrator pump spit fuel with the other tank, so im pretty sure its ign related. As far as the coils burning out it takes about 15 mins of trying to get it to stay running. Then I think leaving the key on doesnt help

 

[fordmann78]

To measure the resistance wire take the wire off the + side of the coil and remove the power feed wire off the electric choke. You should get 1.8-2 ohms between the 2. The wire from the dist goes to the - side of the coil not the + side. That could fry a coil. You should have 9 volts at the + side of the coil. Go directly to ground with your other lead on your multi meter not the - side of the coil. If your resistor wire is bad there is a replacement available.

 

[jo8330]

Thanks ford guy. since that wire is supposed to go to the - of the coil, and it was on the positive, could that fry the points as well ? (It goes from the points to the hot side) Ill see what I get on the meter tomorrow and post the results.

 

[Eric 3.7LX Alpha 1]

Here is Service Manual #3 attached. It will open on the page for Engine wiring for your 470. The link is for the whole manual just flip thru the pages as you need.

As mentioned already your black wire from the distributor is on the wrong terminal. There should be 2-wires on the (+) side of the coil, a purple resistance wire and a purple wire with yellow stripe which runs to the starter solenoid.

The purp/yellow wire will feed the coil full battery voltage when the engine is cranking over by the starter (key in the start position), when the key is released to the run position, the yellow/ purple wire is open (no power) from the solenoid. The coil gets power now from the resistance wire off the choke terminal (key in run position). The purple/yellow wire will read reduced voltage still but will be fed from the resistance wire, not the starter solenoid.

If you don't have full power from the purp/yellow wire during engine cranking she's not gonna start. Time to test the purp/yellow with a voltmeter when cranking the engine over.

The (-) on the coil should have 3-wires: the black from the distributor, a grey to the shift interruptor terminal block, and another grey wire running up to your tachometer as the sender wire.

forgot the link:
http://boatinfo.no/lib/mercruiser/ma...ser3.html#/382

 

[jo8330]

Thank you so much eric. Thats a wealth of info I really needed. Actually the wire.coming off my.dist. is red, so the previous owner was trying to do something. When I get home lster ill throw a meter on it.

 

[Eric 3.7LX Alpha 1]

The worse thing to do is rewire these engines without the correct colors. Makes it much more difficult to troubleshoot. At least with the manual you know where the wires are suppose to go.

 

[jo8330]

Key on. At the coil 12.2 volts. At the choke - 12.2 volts. Ohms between choke and coil on purple wires - 02.4 (I think I did it right lol) Unfortunately I couldnt get a reading while.cranking cause I didnt have anyone to help. Will get my to do it tomorrow As for the other readings, what does that mean ?

 

[jo8330]

Im assuming my resistance wire is no good if im getting full voltage with just the key on correct ?