No spark on Merc 85hp

[ryanmul57]

So I have this 85hp Merc I've been working on for some time now and I have replaced the cranking motor, starter, rectifier, distributor, starting coil, both internal and external wiring harnesses and my battery is new. I am still getting no spark from any of the leads, could this be a sign of a bad switch box or is something else wrong?

 

[ryanmul57]

I would also like to add that my cranking motor was getting very warm when trying to start up the engine, is this because its pulling too much voltage from the battery or could it be a wiring problem?

 

[ryanmul57]

Can someone also tell me on the sliding shifting mechanism where forward, neutral and reverse are so I can install my shift and throttle cables correctly swell as put my lower unit on in the right gear.

 

[Chris1956]

What year or better yet, does it have a distributor and 4 cylinders?

On the shift slider. Normally fwd is toward the front of the boat, and reverse is toward the back. Neutral is about in the middle of the shift slide track.

 

[ryanmul57]

What year or better yet, does it have a distributor and 4 cylinders?

On the shift slider. Normally fwd is toward the front of the boat, and reverse is toward the back. Neutral is about in the middle of the shift slide track.

73' and yes it has a distributor and is 4 cylinder

 

[Chris1956]

The CDIElectronics web site should have a battery-powered CDI ignition test. It will test everything but the trigger. If the test produces spark, suspect the trigger is bad.

 

[ryanmul57]

ok so I jumped the switch box with my battery from a video I saw online and I got sparks in all 4 of my spark plugs, my battery is full and I just tried to test her out and it wouldn't turn over but I was seeing some sparks on my tester. After about a minute though, my flywheel starts to stop spinning fast and my starting motor gets pretty warm because it is pulling a lot from the battery. Is this because its is cold outside or is it not turning over because its cold outside maybe???? Why does it start to slow down ?? Let me know suggestions.

 

[racerone]

You are not supposed to crank for more than 10 seconds.

 

[ryanmul57]

You are not supposed to crank for more than 10 seconds.

do you know what could be the problem if it isn't starting up. It has been about 40-50 degrees today.

 

[Chris1956]

She should crank more that 10 seconds, w/o slowing down. Look for corrosion on your battery cables. It could be under the insulation, so look for bulges.

Engines need spark, timing and fuel to run. Spray some 50::1 fuel into the carb intakes and then crank her. If she backfires or doesn't fire, suspect timing or spark quality. If she runs a few seconds, suspect carbs.

 

[ryanmul57]

threw some 50:1 in and got a second where it tried to turn over but did not. I cleaned my battery cables and the battery corrosion my carbs are cleaned out and sparks are new but my starting motor still is losing some power after only a few seconds.

 

[Chris1956]

Check those battery cables over closely. On my '77, the cable rotted out high up on the gunwale, under the insulation. It had only 3 strands left. The starter ran full speed for 4 seconds and then slowed as the 3 strands heated up.

 

[1960 Starflite]

My 1975 (850) wiring was past toast. I had to replace everything. Mercury corporation must have subcontracted the harness on the cheap for several years

 

[ryanmul57]

damn ok, just replaced the harness not 2 months ago but i will check to see what i can find

 

[Chris1956]

If your starter is not spinning for more than a few seconds, you have electrical resistance, or perhaps a bad starter.

 

[merc850]

If you put a voltmeter on the + starter terminal and the cowl ground read the voltage while turning over the motor, it should be 10-12 volts if your battery is good. If it does fall in this range your starter probably needs rebuilding/cleaning (brushes). A small engine electrical shop could fix it.
Setting up the cables

 

[Chris1956]

I have always heard that the battery voltage on a good battery should not fall below 11.5VDC when cranking if the battery and starter are good.

If you see higher voltage in the battery, and the starter is not spinning fast, the battery resistance is likely the cause.

 

[ryanmul57]

should i have a dual battery system for my 85hp or will one do?

 

[racerone]

One good battery will do.----Use booster cable directly to the starter to eliminate the cables / solenoid as the culprit.-----Find the issue with the system.----Take starter apart.----Very easy.----Then do an ohm test on armature.------Perhaps replace brushes.----Inspect cables.----Not sure why simple trouble shooting and 12 volts is sometimes a big challenge.

 

[merc850]

One marine starting battery not a deep cycle one.