Unknown Ignition problem Thunderbolt 200 20hp

[rIVERMAN559]

Hey guys, i recently purchased a Thunderbolt 200 20hp engine for 200 dollars. The guy said that he had it running for a while and put it in storage. Now the thing doesnt have spark on either cylinder. The sparkplugs look good
I was thinking the ignition coil was bad or the wires may be old and rusted. What do you guys suggest doing?

I have access to my dads volt meter but since he has passed away i dont know how to use it, think anyone could help me out and tell me what to try?

THanks,
Doug

 

[rIVERMAN559]

Re: Unknown Ignition problem Thunderbolt 200 20hp

anyone?

 

[7920hpMercury]

Re: Unknown Ignition problem Thunderbolt 200 20hp

Couple of suggestions:

First you need to figure out what year it is so that you can identify what ignition system you have. Look on an aluminum plate between the transom clamp screws, I think it is a 7 digit number. Also might be on the block where the tell tale hose connects to the block. Or on the starboard side near back near middle or on port side near top near crank halves split.

Second, check this site or other for year and get a Mercury manual off ebay or direct. It is also good to have a parts list which you can get direct from Mercury too. I also like Seloc service manual too. I think you can check everything except the switchbox with a voltmeter/ohm meter. And if everything checks except the switchbox, it is likely the switchbox. A DVA meter can check your switchbox too. But hey, you might have points and no switchbox, need to get the serial number first. Outstanding website, lots of knowledge here to help you get it going! Good luck and great motors!

Another thought, you need to check the compression first since a great working ignition will not help this. Should be 100psi+ on both and within 10 to 15psi of each other. Also check lower unit oil for water.

 

[rIVERMAN559]

Re: Unknown Ignition problem Thunderbolt 200 20hp

I just got my motor back from the shop and the guy said the ignition switch box was bad and the trigger is working but going bad. He quoted me 300 for a part and 300 to put it in. Where can I get this part so i can put it in myself, i checked ebay but cant find it. Anyone know a place?

 

[7920hpMercury]

Re: Unknown Ignition problem Thunderbolt 200 20hp

I like Kenyon Power Boats in Tampa Fla. Also check around on the internet. That sounds too high to me. A service manual will tell you how to swap both out. A parts list from Mercury direct will show exploded views of all parts and part numbers. Fairly straightforward job and I would do it yourself. You need a puller to pull the flywheel. A steering wheel puller from an auto store and a plumbing strap wrench will work. A torque wrench to put the flywheel
nut back right. Also check all of the wiring for deterioration.

Good luck and great motors!

 

[longjohn119]

Re: Unknown Ignition problem Thunderbolt 200 20hp

Holy moly, 300 bones labor to install a switchbox?

That's between $150 and $300 an hour labor

I'm getting out of the commercial HVAC business and going into boat motor repair

I'd probably be looking for a used switchbox on eBay and installing it myself, if you have a digital camera, take pictures of the old one while it's still on the motor and then you'll have a reference for the wiring in case you get confused. A service manual would be prudent also even if all you plan to do is basic maintenance