1970 Merc 20hp no spark

[yam350yfm]

I am looking at a 1970 Mercury 20hp tiller motor that has no spark. It says "Thunderbolt Ignition" on the front of the motor cover. What components could be the problem so I can check parts costs on iboats before I buy the motor. Thanks.

 

[Laddies]

Re: 1970 Merc 20hp no spark

Could be anything from a bad wire to stator, points or insulator blocks

 

[1976SRV190]

Re: 1970 Merc 20hp no spark

Nope, the thunderbolt had no points. It was Mercs pointless ignition. it can be a number of things, lets discuss them in order of cheap to friggin expensive!

On that Merc 200, in 1970 it does have points. Grounds, check ALL motor grounds.

Check the distributor is in right and is timed right static timing before buying anything new. Usually the points have slipped if it has no spark, or are so bad, they need to be replaced, here's a link to see what everything looks like.

http://www.eastcoastmarineservice.com/ignsys.html#336-3996a7

I'd say if it IS a 1970, it probably has a different cowl on it since I think the thunderbolt came out later, like in 1975, but I may be wrong. Hopefully it isn't the switchbox, that can get expensive. But still that part is only about 200 bucks for that motor.

 

[Chinewalker]

Re: 1970 Merc 20hp no spark

Yep, I'm pretty sure the maker points style ignition (points under flywheel and coils mounted on rear of powerhead) was referred to in the literature and on cowlings as the "Lightning Ignition"...

I've found these maker ignitions have issues with the original wiring having the insulation cracked or just plain missing. Go through that and make sure the points are clean and dialed in correctly. As 1976SRV noted, hope it isn't the switchbox assembly...
- Scott

 

[Laddies]

Re: 1970 Merc 20hp no spark

Well 350, it becomes clear the the srv 190 man has never worked on a 70 Mercury 20 HP or even checked a parts manual, as they do have points, a stator and coils the stator is available through CDI, the points from sierra and coils from Mercury, the engine has no switch box the function is built in the stator. Heres a link showing the parts http://www.mercruiserparts.com/Show...r=20&bdesc=FLYWHEEL,+STATOR+AND+IGNITION+COIL

 

[1976SRV190]

Re: 1970 Merc 20hp no spark

Well 350, it becomes clear the the srv 190 man has never worked on a 70 Mercury 20 HP or even checked a parts manual, as they do have points, a stator and coils the stator is available through CDI, the points from sierra and coils from Mercury, the engine has no switch box the function is built in the stator. Heres a link showing the parts http://www.mercruiserparts.com/Show...r=20&bdesc=FLYWHEEL,+STATOR+AND+IGNITION+COIL

find where I said it didn;t have points, I said the Thunderbolt didn't have points....it is a breakerless style ignition.

 

[1976SRV190]

Re: 1970 Merc 20hp no spark

Here's a number from Mercury for your points....that model does not have a switchbox so you are very lucky.

336-4318A2 points set for 20hp motor 1970, and others.

 

[Laddies]

Re: 1970 Merc 20hp no spark

find where I said it didn;t have points, I said the Thunderbolt didn't have points....it is a breakerless style ignition.

Maybe Mercury don't know that because they refer to it as Thunderbolt, as they do any CD. ign. system.

 

[yam350yfm]

Re: 1970 Merc 20hp no spark

Thanks to all for the help. I guess what worries me is the cost of the stator if that is what is causing the problem. I have been working on a 1957 Johnson 18hp and this Merc came up. The 18hp has been causing me some problems, but the ignition was easy to work on and inexpensive (around $55 for both sets of coils, points, and condensers).

 

[1976SRV190]

Re: 1970 Merc 20hp no spark

Thanks to all for the help. I guess what worries me is the cost of the stator if that is what is causing the problem. I have been working on a 1957 Johnson 18hp and this Merc came up. The 18hp has been causing me some problems, but the ignition was easy to work on and inexpensive (around $55 for both sets of coils, points, and condensers).

I looked at the parts and nothing is very expensive. I would inspect everything and replace anything that looks worn out or in jeapordy of wearing out. You don;t want to chince out on something that may leave you stranded on the water.....

 

[Laddies]

Re: 1970 Merc 20hp no spark

While the stator is pricey at $250+, the system is easily checked with a OHM meter. If you need the specs later we can post them.