1971 Merc 800 wont start

[rtpassini]

-Compression is 130, 140, 120, and the last cylinder i dont know. i couldnt get the compression tester in there.
-Spark is good.
-Tried spraying fuel into carbs (well just the top carb) no change at all.
-It just cranks, no fire at all.

I bought the boat with the previous owner saying the starter was bad. I re-did all the wiring and put a new starter in. It cranks so thats a start. The choke works.

What else should i try? can it be a wiring issue? If the spark plug wires are wrong can it cause this? i would think it would at least fire a litle...

HELP PLEASE! its getting nice out

 

[Boatist]

Re: 1971 Merc 800 wont start

I do not know your motor but if you have compression and a good spark and fuel in each cylinder then the only thing left is the timing.
Put a timing light on it and make sure the timing is corect.

After that I would start over. How did you check the spark?

 

[Chris1956]

Re: 1971 Merc 800 wont start

That motor should have a distributor and a single coil. There is a test for the coil and switchbox, posted on this website, and also at Dolphinmarineservices.com. You might search on Ignition test in the merc section of this site.

 

[Chris1956]

Re: 1971 Merc 800 wont start

By the way, For that motor to have spark, the ignition coil need to provide +12V to the white wire on the switchbox's starboard side. There should also be +12V on the red wire on the switchbox. Without these two signals, there will not be any spark.

 

[rtpassini]

Re: 1971 Merc 800 wont start

to check the spark i pulled the plug and grounded it while cranking.

a nice blue spark came out.

is there a kill switch anywhere with these?

 

[rtpassini]

Re: 1971 Merc 800 wont start

also, there isnt any sputtering or sounds of firing.. the flywheel just spins. which is why im wondering if theres a kill switch? i didnt think so though....

 

[Chris1956]

Re: 1971 Merc 800 wont start

There was no factory kill switch on those. Also, a kill switch kills the spark. You said you have spark.

So you have good compression and good spark. Spray some 50::1 fuel mix into the carbs, close the choke plates and crank her up on the flush device. if it fires, runs a few seconds and dies, the carbs are likely clogged up and need to be rebuilt.

 

[rtpassini]

Re: 1971 Merc 800 wont start

while cranking, i tried spraying fuel in and nothing happened.

should i hold the sprayer right at the carbs and squirt then close the choke?

 

[Chris1956]

Re: 1971 Merc 800 wont start

It is hard to flood those motors. Give a couple of sprays into each carb and close the choke plates. There should be a black choke knob on top of the cowling suport, that you can use. Put the cold start lever all the way up.

 

[rtpassini]

Re: 1971 Merc 800 wont start

gave it a try. there wasnt any change. it didnt catch even a little. just kept cranking.

im stumped.

 

[Moody Blue]

Re: 1971 Merc 800 wont start

If you have spark and you have fuel, then you must have fire IF the two are present at the same time.

You must have the plug wires mixed up. Probably getting spark to cyl without fuel, and fuel to cyl without spark, therefore no fire.

Have you connected a timing light to #1 cyl to verify timing?