50hp Merc only 2 cyclinders

[brusman]

I have 50 hp store for about a year after replacing the fuel and rebuiding the carbs it only runs on the bottom 2 cyclinders. If I remove plug wires they still create spark

so far I have replaced the stator and trigger.

Still did not fix problem

I have completed the following
Check coil ohms ok to specifcations
Swapped coil primary leads problem still exist

when I reoved the plugs the 2 not working have fuel
i have adusted carp to spects but note if i take the top carb and close the needle valve it still does not change the RPMs.

I disconected the rectifier and still no change.

The only thing I have not completed is the voltage check and I'm not sure how to do this can you help

Also I suppect at this time the power pack how can i checkl this.

The only thing else is the reed valves??? how can I check for this

any answer would be helpful. thanks frank

 

[Laddies]

Re: 50hp Merc only 2 cyclinders

Are you saying you have spark on all 4 cyls. or just 2?

 

[rodbolt]

Re: 50hp Merc only 2 cyclinders

how many cylinders and how many carbs?
also if you had spark why replace an ign producing part ?

 

[Silvertip]

Re: 50hp Merc only 2 cyclinders

I think he has a three cylinder and I too wonder why you replaced electrical components when you have spark on all cylinders. Always, Always, check the cheap stuff first. First, closing the idle mixture screw on an otherwise dead cylinder will obviously not make any difference how the engine runs because the cylinder is already dead. If that plug is bone dry, that cylinder is not getting fuel so since you've been in those carbs, you may have done something wrong on that one. I would first check that the float level is set correctly and that the needle and seat are correctly installed If you set it too low or installed things wrong, fuel can't get into the carb. With the engine running, squirt a fuel/oil mixture into the throat of that carb. If that cylinder begins to fire, you still have a carb problem. Are you sure you have the fuel lines routed correctly after the rebuilds. Lastly, have you done a compression check.

 

[brusman]

Re: 50hp Merc only 2 cyclinders

I think he has a three cylinder and I too wonder why you replaced electrical components when you have spark on all cylinders. Always, Always, check the cheap stuff first. First, closing the idle mixture screw on an otherwise dead cylinder will obviously not make any difference how the engine runs because the cylinder is already dead. If that plug is bone dry, that cylinder is not getting fuel so since you've been in those carbs, you may have done something wrong on that one. I would first check that the float level is set correctly and that the needle and seat are correctly installed If you set it too low or installed things wrong, fuel can't get into the carb. With the engine running, squirt a fuel/oil mixture into the throat of that carb. If that cylinder begins to fire, you still have a carb problem. Are you sure you have the fuel lines routed correctly after the rebuilds. Lastly, have you done a compression check.

 

[brusman]

Re: 50hp Merc only 2 cyclinders

It is a 4 cyl 50 hP 1985 I did an ohm check in the stator and it check bad so I replaced, I replace the trigger just for the heck of it.

It is 1 and 2 that are not operating, but yes there is a spark. the Plugs in 1 and 2 are wet with fuel.

I rechecked the carb rebuilt and it seems ok fuel is entering the carb and bowl is full, the plugs are wet with fuel on 1 and 2

I will try your idea with the fuel

Yes did a compression check all well above normal

i have also changed swapped coil and coil primary leads and still no help.

Do you know how to check the power pack, ( trigger box) I was told though that since i had spark on 1 & 2 it was not the trigger box

Lastly how do you check or know if something is wrong with the reed valves??

This motor power head was rebuilt about 3 years ago and hardly used by my father.

Thank for your comments

 

[Silvertip]

Re: 50hp Merc only 2 cyclinders

If the plugs are wet with fuel it's obviously getting fuel so that goes back to the spark issue. An engine needs fuel, air, spark, compression, and everything needs to happen at the right time. Are you sure you have the wires on the right plugs? Have you done a compression check. And most importantly, does the spark intensity on 1 and 2 compare with that on 3 and 4. The spark should be a sharp blue snap and jump at least a 3/8 inch gap. Anything less than that means it will probably not fire under compression.

 

[Laddies]

Re: 50hp Merc only 2 cyclinders

If you had a reed out the engine would still run alright above 1500 RPM, 1+ 2 share a stator winding so swap the red + red/white wires and the blue/blue/white wires to ck the stator windings, they also share a trigger winding so OHM test the trigger wires, if both test show up good there is a good chance the switch box is bad. It's the type of trouble that you really need a DVA to test for, as OHM meters won't show low voltage

 

[brusman]

Re: 50hp Merc only 2 cyclinders

If the plugs are wet with fuel it's obviously getting fuel so that goes back to the spark issue. An engine needs fuel, air, spark, compression, and everything needs to happen at the right time. Are you sure you have the wires on the right plugs? Have you done a compression check. And most importantly, does the spark intensity on 1 and 2 compare with that on 3 and 4. The spark should be a sharp blue snap and jump at least a 3/8 inch gap. Anything less than that means it will probably not fire under compression.

 

[brusman]

Re: 50hp Merc only 2 cyclinders

the wire are correct, and the engine will start and run but only at a fast idle, but even when it running at higher RPm and I remove the 1 or 2 wire the engine does not change it RPM

Yes did a compression check and all cyl are equal over 100

It seem that all spark is blue and snaps

 

[Silvertip]

Re: 50hp Merc only 2 cyclinders

If pulling a plug wire has no effect on a running engine that says that cylinder is dead. If you spritz some fuel in the carb for that cylinder and it picks up, you have a fuel issue. If not, its a spark issue. JNust because the engine starts does not mean those two cylinders have spark.

 

[brusman]

Re: 50hp Merc only 2 cyclinders

How do I complete a DVA test

 

[Laddies]

Re: 50hp Merc only 2 cyclinders

If you have a DVA avialable to test with the red + red/white wires should put out 25V+, the blue + blue/white should be 180V+ - the trigger wires should put out 4V+ and the lead wires to the coils 180V+

 

[brusman]

Re: 50hp Merc only 2 cyclinders

Well I found out why:/

It seems even lthough I was getting spark on all 4

2 of the plugs were bad ----:$

I was told when the stator went bad it loaded up the plugs and because it sat for a while the fuel damaged the plugs.

i replaced the plugs and after starting there was a noticable difference. wow.

However did a sea trial today and the motor would not power up and the boat woulds no go on plane .:'(

Any ideas

 

[Silvertip]

Re: 50hp Merc only 2 cyclinders

Once again, squeeze the primer bulb when you are trying to get going. If the engine picks up you have a fuel delivery problem. Bad fuel pump, dirty carbs, clogged pickup in the fuel tank. Have someone give a spritz of fuel into the carb intakes when trying to get on plane. Again, if it picks up it points fo fuel problem.

 

[brusman]

Re: 50hp Merc only 2 cyclinders

Already tryed that, any other ideas.

 

[Silvertip]

Re: 50hp Merc only 2 cyclinders

Did you pull the plugs to see if they were fowled again?