OMC mechanic in over head with 50 merc

[a.d.mobile]

Well i have a 50 classic ser A196055 1986? and it is a classic this belongs to a friend? i guess if he was a good friend he would have a omc ok ok. here we go first it had carb problems rebuilt carbs found bad pump diaphrams. he ran boat 6 times ran great. then i get the dreaded call runs like $hirt. checked spark 1 cyl not fireing taped switch box and wamo spark. put a CDI after world box on good spark on crank plus at idle on hose remove wires 1 at a time and she is a welder. take it to the lake and what a dog like it is running on 2 cyl pulled new plugs for inspection #1 good #2 all wet no signs of burnt fuel #3 good and #4 same a 2. motor has 125psi in all holes. tore carbs down again every thing is good in there. how does that triger work fires 2 cyl at a time? then the other 2? sorry this is a book. thanks A.D.

 

[clanton]

Re: OMC mechanic in over head with 50 merc

The last one of these I worked on, the black plastic venturi in the lower carb was missing, I never remove these, and missed it when I cleaned the carb.

 

[boatmanwayne]

Re: OMC mechanic in over head with 50 merc

Hey there A.D., I've worked on several of those 50's, Curious to know what you have your initial idle mixture screws set at from lightly seated, let me ask that and maybe I can get a starting point.

 

[a.d.mobile]

Re: OMC mechanic in over head with 50 merc

black plastic venturi are new came in merc carb kits, i replaced them. the idle mixture is at 3/4 out on both i can turn them in and lean it out or out to rich it idles the best at 3/4. idle seems ok. when running loaded in the lake it seems to drop #2 and #4 cyl i am only going by plug condition canot pull wires on plane yet i need a driver. thanks for the replys im working on it now. i looked under fly wheel the trigger seem to have 2 sensors i am asuming one fires 1&3 and the other 2&4???????

 

[The Marine Doctor]

Re: OMC mechanic in over head with 50 merc

If you have access to a DVA tester...you can test all the electronics on the engine...I do not think that you have a fuel problem...I would lean more towards the stator output being a problem.<br /><br />TMD

 

[a.d.mobile]

Re: OMC mechanic in over head with 50 merc

thanks for the reply doc yes i have a dva but no book to tell me what values im looking for nothing is grounded. removed stator screws to look for corosion looks good. while driving the motor is smoth you cant feel a hard miss so the 2 cyl im having problems with must be opposed. the wild thing is it has spark at idle but seems to drop on acc-<br />i cut the tie straps that hold the trigger harness so i can move it maybe broke wire here? going to the lake tonite with timming light to see if it is droping spark on acc, or am i wasting time? thanks AD

 

[a.d.mobile]

Re: OMC mechanic in over head with 50 merc

well did the parts peplace trick stator/trigger still does the same thing this thing might have scored cyl walls getting a bore scope to check it out. did run boat with a timming light on each cyl steady light on all cyl. did not look at the carbs with light to see fuel flow? any ideas out there?

 

[a.d.mobile]

Re: OMC mechanic in over head with 50 merc

well i got it thanks to those who tried it ended up being a new bad switch box. after checking the new stator and trigger and they were good i ordered a new switch box and bang were off!!!!