4.5 hp missing bad

renoduckman

Petty Officer 3rd Class
Joined
Mar 31, 2006
Messages
75
I need some help from any of you outboard techs please. I have a 1979 Merc 4.5 hp serial number 5397758. It has a bad miss, on the low rpm side. The plug and wire are fine. I have what appears to be the Thunderbolt phase maker cd ignition with points. I have 2 manuels but the dont seem to be exactly what i need. I pulled off the flywheel to be sure . If any body has any specs on how i can trouble shoot this system i will apppreacite it. I have a good meter and an electrical background. Thanks Joe
 

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: 4.5 hp missing bad

First think I'd check are the points as they may need servicing. These points tend to get rather nasty looking as they handle very high voltages, but you can dress them up and regap and usually they're quite serviceable.<br /><br />Also check out the insulating block where the points wire passes thru to the points connection. This insulator cracks then high-voltage will leak to ground causing problems. You can find parts breakdown illustrations at this site:<br /><br /> http://www.dougrussell.com/partscatalog/ <br /><br />The insulator I'm referring to is Part No: <br />"336-4460; INSULATOR, CABLE TO CONTACT HOUSING"<br /><br />The other thing to look for on these is an arcing coil. Pull the coil off and take it out of its plastic housing. Inspect all visible areas of the coil for arc/burn marks. Sometimes they will 'leak' so badly you can hear the arcing/sparking when the motor's running.<br /><br />One last thought, check the kill switch for high resistance as it "normally closed" to complete the ign circuit. Bad conn's or bad switch could cause intermittant problems and poor running.<br /><br />HTH and keep us posted.........ed
 

renoduckman

Petty Officer 3rd Class
Joined
Mar 31, 2006
Messages
75
Re: 4.5 hp missing bad

Thanks Ed MC. The points look bad so thats the place to start. I have to find out the spec for how to set those? What i have is not exactly the same as my manuel and what you have told me.I guess its odd or what? I have one set of points, a high and a low speed coil under the flywheel. My kill button doesnt appear to be normally closed, as you and my diagram are showing. It is connected to the engine block and goes to the terminal on the coil that fires the plug. It appears to ground it out. I will check again but i unhooked it and it didnt seem to have any effect either way. Id like to find the specs on how to ohm out the coils and such under the flywheel. My book has some but they dont appear to be exactly correct for my engine. I will keep you posted when i get a chance to look at it again tommorrow. Thanks
 

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: 4.5 hp missing bad

OK, looking at your post I realized I totally blew past the Ser # etc and your motor sounds like it has a Type VII Phase-Maker system. The points do handle high voltages (around 1000 according to the manual) and if they look really really nasty, it might help to pull them out, clean up and re-gap to .020" This ign actually fires when the points Close!! The book does say that some pitting of the points is "normal" for this ign type.<br /><br />You're right too about the kill button, it's the older type of ign they used on these beasts that grounds to run. Yours should ground to kill I expect. This type of kill switch can have a 'leakage' problem to ground which causes intermittant sparking, a simple diagnostic method is to disconnect the kill switch wire to see if things improve.<br /><br />My Seloc manual has a section for Hard Starting or Poor Low-Speed Performance troubleshooting as follows:<br /><br />"TAKE TIME to make a color code diagram of the electrical leads before disconnecting them. The color code terminals will be used during the tests and the diagram will ensure each lead will be reconnected to the proper terminal. Remove the four generating coil leads, the capacitor lead, and the heavy green leads from the electrical module. <br /><br />Use the VOA range at RX100 and check the low-speed resistance between the red and yellow coil leads. The reading MUST be 32-40.<br /><br />Check the forward resistance of the recifier: Connect the red lead of the meter to the electrical module terminal from hwich the red coil was disconnected. Connect the black meter lead to the terminal from which the capacitor lead was removed. Use the VOA range at RX100 and check the resistance. The reading MUST be 10-15. Check the reverse resistance of the rectifier; Reverse the meter test leads, and use the VOA range at RX100. There must be NO reading."<br /><br />Anyway, hope that clears things up a bit, sorry about the Bum Dope earlier. G'luck.........ed
 

renoduckman

Petty Officer 3rd Class
Joined
Mar 31, 2006
Messages
75
Re: 4.5 hp missing bad

Ed MC, thanks for the advice. I wil hopefully work on this again sunday. I will try to ohm everyting out again . The points do look really bad so im going to approach that first. I seem to have a good engine, other than the miss. Is it just me or are the parts high priced for these old motors? I will keep you posted. joe
 

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: 4.5 hp missing bad

You think they really want you to FIX these old motors? HA!! They'd rather have you buy a new one which is likely designed to last half as long as some of the older ones did. <br /><br />I don't expect OMC (for example) figured that 40-50 years later we'd still be working on old J/E kicker motors but they sure were built well enough to last. Old Mercs don't do too bad in fresh water, either. I've seen a lot newer motors that were already junk after 10-15 years. <br /><br />Thank goodness for the aftermarket, you can still get lots of Sierra parts for 'reasonable' prices.<br /><br />I have a real nice '77 4.5 Merc that just needs a lower crankshaft seal. Unfortunately it's a dealer-only part which was over $40 last time I checked. Kinda steep but they've got you over the barrel. Time to bite the bullet I suppose and go see the $tealer!!!! ;)
 

renoduckman

Petty Officer 3rd Class
Joined
Mar 31, 2006
Messages
75
Re: 4.5 hp missing bad

Ed Mc,<br />The motor seemed to ohm out ok. Unless im crazy or forgot how to read ohm meter! I cleaned up and regaped the points, even though i dont think that was the problem. It still seemed to run the same. Just for the heck of it i took it out this weekend and trolled for about half hour with it. It ran pretty well. I still think it has a lower end miss but my dad thought it was fine. I will play with it some more. It did run well though. Once it sped up and died on me. Then it seemed to need choke to restart. Other than that it was ok. I think i need some carb tunning but will give it some more hours here soon. The lake i was fishing at was 5700ft so thats tough. I will keep you posted. Thanks for the help. joe
 
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