1978 Mercury M-800 starting issues

[Kissdude]

Hello there,

Wonering if someone could help me out here. I have an older 1978 Mercury M-800 and my issue is.. when I pull the starter out and hook up 12 volts it runs perfect but when I install it, the flywheel stalls and doesn't turn very good. I am using a fully charged battery, connections are all good and plugs are out. I have tried to connect 12 volts up after solenoid but its doing the same thing and won't turn consistenly to check compression.. Any help would be appreciated thanks.

 

[Kissdude]

Ok guys,

With my plugs removed this engine turns over not bad but if I put a compression tester on one cylinder, it will hardly turn over! What is going on here?

 

[jbcurt00]

Stop posting in the FAQ forum, it's for reference only

As they had the same title, 2 topics were merged & moved to the Merc outboard forum

 

[Kissdude]

Hope this is the right place to write. I’m having troubles with my 1978 Merc M-800 doesn’t turn over well with plugs in but will turn over good with plugs out. Could this be a stuck in gear issue or am I missing something?

 

[Kissdude]

Stop posting in the FAQ forum, it's for reference only

As they had the same title, 2 topics were merged & moved to the Merc outboard forum

Very sorry, I’m still new here!!

 

[racerone]

Take the starter apart for inspection.----Load test the battery.----Inspect battery cables.

 

[Kissdude]

The battery and cables are new. What ya thinking.. brushes?

 

[Kissdude]

I have tried 3 starters and get same result. I did however forget to mention that the engine hasn’t run for about 8 years now.

 

[racerone]

I guess I missed the part about the 3 starters.----Good luck with your motor.

 

[Chris1956]

Mercury starters are usually held in place by rubber mounts. They therefore need a good ground cable to the block. You might check yours for corrosion.

 

[Kissdude]

Thanks, I will go over wires again

 

[Kissdude]

Is there such thing as exhaust ports being plugged that would keep starter from turning properly?

 

[racerone]

Well, yes the exhaust could be plugged with a mouse nest.-----But pull it over with a rope on the flywheel as a test !

 

[Kissdude]

Silly question but how do I turn this M800 Mercury off when I get it started, control wires aren’t hooked up.

 

[Faztbullet]

Either choke it or plug harness back in with key in off position