carbs or coil(s)?

evilgenius518

Recruit
Joined
Apr 27, 2010
Messages
4
Hi all, so I have a 74 Johnson 50hp (74esl50m) I am wondering if I have a carb problem or a problem with one or both of the coils. A few weeks ago my motor was giving me a real hard problem starting. I pulled the top plug and it started right up, I did this on two separate occasions but once it started for the day that once without the plug, it would run fine. I changed to new spark plugs and that sorta seemed to fix the problem. Now today I am driving the boat to the cove at wot and about half way there it loses power but not fully , about half throttle and is running very sporadically. When I throttle down it runs like normal, bring it up and runs like I said. I checked fuel tank valve, pumped bulb and no changes. I chill in cove for a bit start it up go WOT and again about half way it starts acting up so it seems to me that it's Is happening when it heats up, or is it just emptying the bowls and clogging the carbs? I normally clean the carbs right out at the beginning of season and did not this year for whatever reason. I'm pretty sure the coils are the originals too. So what's the deal? Carbs filling up, emptying and clogging OR one of the coils shorting out when motor warms up. I'm not really sure how to go about testing the coils resistance with my multi meter. One plug dose look better then the other when I took them out to look at then but that still doesn't tell me much cause that could be from either of there issues. AS ALWAYS, any and all help is much appreciated.
 

Captain Jaxon

Seaman Apprentice
Joined
Jul 24, 2010
Messages
30
Re: carbs or coil(s)?

You may want to check compression on that cylinder if it was continually the same one acting up.
 

mrcj001

Petty Officer 1st Class
Joined
Jul 25, 2008
Messages
313
Re: carbs or coil(s)?

It sounds like a fuel issue

Check all fuel lines for air leaks. Check vent cap on tank, be sure its venting.

Blow air thru fuel lines from engine to tank, make sure they are clear.

Check tank pick up line and check primer bulb.

If primer bulb doesnt get hard, it may need replacing.

If ignition coils are cracked, they need replacing.

You can trouble shoot ignition here:

http://www.boatpartstore.com/page30.asp
 

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: carbs or coil(s)?

Swap coils wires & plugs. Give it a run. If the problem goes to the other cylinder you know that one of those parts are defective.
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: carbs or coil(s)?

start at the begining of trouble shooting, compression and spark test. you must know this, before anything else.
 
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