1970 Merc 7,5 no start

Keadymen

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Oct 1, 2003
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I got a 7.5 Merc Thunderbolt with no start, it was at the family cottage. The "word" is it needs a new "control box" . What does that mean and how much ?
 

The Marine Doctor

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Jul 25, 2003
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Re: 1970 Merc 7,5 no start

If you supply with a serial number give you more information concerning your engine.<br /><br />TMD
 

Chinewalker

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Aug 19, 2001
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8,902
Re: 1970 Merc 7,5 no start

If the motor is in fact a 1970 model, then it should have the low-tension magneto (maker points under the flywheel inside a green solid state donut) and two coils on the rear of the powerhead. The donuts are usually the cause of no spark, although the points can get pretty crudded up. Problem is the donuts go for about as much as the motor is worth, if not more...<br />- Scott
 

Keadymen

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Re: 1970 Merc 7,5 no start

It definately has the two coil at the back, the the stator is inside a red plastic cover, is that where you expect these donuts to be found.
 

Chinewalker

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8,902
Re: 1970 Merc 7,5 no start

If it has the red plastic cover,then it has had the donut replaced at some point. There were two different versions of the low-tension magneto. One with a solid state green donut, about 5-inches in diameter, and the other had the red plastic housing. Inside the housing are two sets of points. Make sure they're clean and gapped at .020. The manual says it's not critical that they be clean because of the voltage involved, but I've had no-spark motors in the shop that have gotten spark with new points... It's worth a shot...<br />- Scott
 

Keadymen

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Oct 1, 2003
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Re: 1970 Merc 7,5 no start

Thanks, I'll give it a try, nothing crazy is going to spring apart if I try and take this apart.
 
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