Merc 4hp mdl 40 ser # 3168761 need info

[crosbyman]

anything special  to know or look for in  reviving this oldy.   nice little motor  thunderbolt ignition ( no condenser ????)    one set of point

impeller  new.     gearcase  has no water… oil replaced…  lower GC  cavity crud removed….  GC   water drain ok      compression ok … I cleaned the point contacts .  flywheel key was  found broken  and now replaced .

 

Nice local  Merc Dealer gave me  2  FW  keys 🙂

starts on a choke and 2 pulls but idles poorly and dies   ….carb job needed  and will be done.      runs fine high speed

looking to  swap the 9.5hp Evinrude  on my rig  for this little kicker.              9.5 hp runs fine but  at 2$ a liter  I can troll just as well

with a 4hp Merc

btw… any benefits to adding a .22uf across the point contacts  ….     I found the points  rather  blakcish with soot

 

 

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• This topic was modified 3 years, 6 months ago by crosbyman.
• This topic was modified 3 years, 6 months ago by crosbyman.

[dave-bernard]

those points are maker points if thunderbolt and should be pitted and poor looking are at their best. look at the idle tube for blockage in the carb.

[crosbyman]

thanks  I will check out the carb

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[crosbyman]

Dave, what about an extra cap on the points …. bad/good  idea  to help  60 year old points ??

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• This reply was modified 3 years, 6 months ago by crosbyman.

[billw]

Dave is right. The points always look bad; so kind of like what he said, bad is good, in this case. Clean them lightly once, gap them and then walk away. Those early Thunderbolt ignitions were sketchy enough as it was. I would not go trying to throw unknown electronic changes into the mix. You could smoke something in the stator. Like so many Mercury things, that ignition is pretty much opposite of everything you have ever known about other engines. If it’s running, don’t mess with it. DO be on the lookout for failing wire insulation and shorts to ground, because of it.

Long live American manufacturing!

• This reply was modified 3 years, 6 months ago by billw.

[crosbyman]

ok thanks  ….  i’ll focus on the carb   🙂

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[crosbyman]

just for info to all interested in  Merc CDI ignition…like phase maker cdi ignition  on this little 4hp  of mine

Mr. B. Mohat wrote and excellent article on the subject  back in Dec 2020

it answers my question about adding a condenser….none needed  !!     since the thing fires the plug by CLOSING the contact rather than openning like our normal magnetos

 

 

enjoy…

https://wrcoutboards.org/wp-content/uploads/2021/02/The-Phase-Maker-CDI.pdf

 

 

 

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[crosbyman]

update….

 

took out  the carb….has suggested       cleaned out the  low speed  tube   to the upper  LS cct …..

readjusted the idle limit  travel which I found out of wack ….closed it up to prevent going to slow and dying.

Engine now runs like  a purring kitten  🙂

 

thanks all for comments

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[billw]

I think ALL the one cylinder Mercs run amazingly smooth for being just one lung.

Long live American manufacturing!

[crosbyman]

paid 0$  for a inherited  “troublesome motor”   which  basically ended up as  simple ignition issue .    the ground wire on the coil   was not even connected  (bolted) properly . it  was just sqeezed betwen the coil  and engine frame. the rest was  the carb job and idle limiter  screw .

field trial coming up next week …it will replace  the  9.5hp kicker on my rig.   touched it up with Mercury black and some  black fingernail polish ….looks pretty good for a 50 year old 🙂

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