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1978 Mercury 800 questions

W

Wimbie

New member
I bought a 1978 Mark Twain tri hull that has an 800 on it. I was told that it ran when parked 12 years ago. Got it back to my place and drained out and put new gas in and tried starting it. Wouldn't you know it, it would fire, but not start. Then after a few more tries, wouldn't even fire. Not sparking on the bottom 2 cylinders. I only paid 600 bucks for the boat and motor, so not upset that I have to replace things on it. Switched plugs and wires, looked at the ignition coils and replaced them because the ferrite was cracked and broken. Same thing so I figured switching. So I thought I better look at everything else before I even bothered changing it. All the wires are bad. The whole harness basically fell apart, wires from stator and trigger are bad from start to finish. So I plan on ordering a new harness, stator, trigger, rectifier and probably switchbox. The wires on the mercury switch are also bad, should I replace this, or do I really need it? Anything else I should do or replace? I appreciate all the help I can get, thank you in advance!
 
You need a new water pump impeller !----Post the results of a compression test.-----Be a shame to spend a small pile of money to find you have a dud motor.----Perhaps pull off the bypass covers to inspect pistons and rings.-----Install new " bleed restrictors " while bypass is off.
 
You are using fresh fuel/oil mix? I get nervous when one states new fuel. Check for spark with a open air spark gap tester easy enough to make if your creative. It mistjump a gap of atleast 7/16 inch gap with a blue snap.
 
Yes, new 2 cycle mix, sorry. I wasn't getting spark in cylinders 3 and 4. That's when I started looking closer at everything and discovered almost all the wires are rotten, corroded and falling apart when you touch them.
 
Yeah, I'm gonna order a stator and trigger because the wires are corroded all the way to them. Probably gonna get a rectifier and switchbox while I'm at it.
 
Do you have the flywheel puller? Do not attempt to pull it with a jaw type puller. It threads center of the flywheel and pops right off with a impact driver. If you have a cordless impact driver get the socket adaptor and give it a shot!
 
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