fouling plugs

[med_student25]

I have an old Merc 500 that keeps fouling plugs. I don't really know what to do. I know mixture is suppose to be 50 to 1, but the idle on the engine is turned up almost at max or the engine will keep dying. I think that I might not be getting enough spark because there is alot of unburned fuel out the back of the motor, but I don't really know how to fix this problem. Any help would be very appreciative.

 

[tashasdaddy]

Re: fouling plugs

how old is old. has the engine ever had a decarb, burning off the excess carbon build up in the engine.? when was the last time the carbs were rebuilt? have you checked, spark, compression? when was the last total tune up, timing, link n sinc. what's the serial number on the transom bracket. and welcome to iboats, you're our eyes and ears. from here i can't tell if it has a pulse.

 

[Barnacle_Bill]

Re: fouling plugs

Cheap oil can cause that too.

 

[Scaaty]

Re: fouling plugs

You need to start by cleaning out the carbs. Its probably got a Magneto Ignition, so pop the cap and toss a new sets of points in there. THEN if you still foul plugs, we can help for there.

 

[JUSTINTIME]

Re: fouling plugs

i would clean carbs
de-carb
replace fuel filters

 

[med_student25]

Re: fouling plugs

Thanks, serial number is 2477823. I think it's late 60's, but can't remember for sure. Will try cleaning carbs out and replacing tips in magneto. Thanks again.

 

[DHPMARINE]

Re: fouling plugs

That's old,but you have to do the basics .....

Spark

Compression

Fuel Sample

Then decide weather carb rebuild or decarb or magneto "tips"

DHP

 

[med_student25]

Re: fouling plugs

does my engine have fuel filters on the engine? My friend's dad told me that I should increase oil mix 25:1 but that didn't sound right. Right now its 50:1 which is what the marine guys in town told me it was suppose to be. My spark at the plugs is good. I had all compression checked in each cylinder about a year ago and they were all within normal range. It just won't idle unless the throttle screw is turned way up.

 

[Vlad D Impeller]

Re: fouling plugs

Compression variances done a year ago would'nt be as reliable as having a test done today, due to the problems which you are now encountering.

At a glance it seems that you may be having a fuel delivery problem, perhaps a partially clogged fuel filter and by adjusting the throttle screw to the max, you may therefore be causing the foulplugs by being too rich.

To find the fuel filter, follow the fuel line, it is probably located between the fuel pump and the carbs.

 

[Harker]

Re: fouling plugs

It probably has the carbs with the float on the side of the carb in a tube..there is a screen in the top cap of the float chamber. They aren't filters in the true sense but catch chunks from poor gas or rotting fuel lines.

 

[med_student25]

Re: fouling plugs

Well guys I tried the fuel filters and they look fine. They are both clean. One of them is a little bent, but I don't think that would cause the problem, would it? I haven't checked the tips on the magneto, but the inside of the engine is really oily. bottom carb intake has a little bit of oil just sitting in the bottom of it also.

 

[med_student25]

Re: fouling plugs

One of my friends was also saying that new plug wires would be good to do because they can build up a resistance in them. Could that be it?

 

[billybones]

Re: fouling plugs

Or try ignoring all that has been told to you so far.

 

[med_student25]

Re: fouling plugs

OK....So I replaced the points in the magneto, replaced distributer cap and spark plugs, and the condensor and still having the exact same problem as before. I'm about to give up and sell the boat, but I thought I'd ask for help before I get to that. Is there anything else that it could be?

 

[izu]

Re: fouling plugs

how old is old. has the engine ever had a decarb, burning off the excess carbon build up in the engine.? when was the last time the carbs were rebuilt? have you checked, spark, compression? when was the last total tune up, timing, link n sinc. what's the serial number on the transom bracket. and welcome to iboats, you're our eyes and ears. from here i can't tell if it has a pulse.

what is link and sync

 

[The-Machinist]

Re: fouling plugs

I would bet my lunch money that the carbs need rebuilt. Dont give up on her yet, you have already ruled out the majority of possible problems.