Wont Idle 1987 merc 45hp

[pdehardon]

I have a 1987 Merc 45hp Classic 50. I was told by the previous owner that the top end was rebuilt 3 years ago. It has run great until yesterday. Now it wont start unless I open up the throttle quite a bit. It wont idle. If I open it up it runs at about 3500rpms for a minuet then clears up and goes to 5000rpms. After running hard it will idle for a minuet and then quits. I checked the plugs. The 3rd down from the top was very fouled. I replaced it and it started and idled for less than a minuet and the problem returned. Any suggestion on where to start?????

 

[pdehardon]

Re: Wont Idle 1987 merc 45hp

I have noticed that I am seeing a lot of arcing from around one plug. This seams to only happen at low speed. I have changed plugs and swaped plug wires. The same cylinder is arcing. Does this sound like a bad coil??

 

[pdehardon]

Re: Wont Idle 1987 merc 45hp

Have rearanged coils. Problem stays with cylinder. I guess its the switch box?

 

[KCLOST]

Re: Wont Idle 1987 merc 45hp

Ok, let's slow down a bit.... Arching around one plug????? That at least tells me that you are getting spark to the cylinder from the box. You've also confirmed that the coil is ok...Did the "problem" as you say that stayed with the cylinder refer to arching or a fouled plug? <br /><br />To check the switch box. Switch the red wire with the red/white wire, and switch the blue wire with the blue/white... They will all be connected at the top of the box. Then see if the problem moves to another cylinder.... <br />Just to let you know, if the problem comes and goes, or clears up at higher rpms, to me it doesn't sound like a switchbox problem... When they go bad they don't fix themselves... But go ahead and check it.<br /><br />Is the arching from the boot to the block? Where is the arching coming from, I guess is my question..

 

[pdehardon]

Re: Wont Idle 1987 merc 45hp

The arching is from around the boot. It archs from under the boot to the base of the plug. Also note I now have a mix of spark plugs(2-champ,2-autolite). I will try 4 new same plugs today. If I still have arching I will try to move the wires as you suggest.<br /><br />In 4 to 5 hours of testing and running I am not seeing any more fouling of the plugs. I dont think the fouling had any thing to do with the problem.

 

[pdehardon]

Re: Wont Idle 1987 merc 45hp

Have installed 4 new NGK plugs. No arching problem, however I still cant idle. <br /><br />I have found something that may be the REAL problem. At low RPMs I see gas squrting from the top carb. It is losing a lot of fuel. On the top right of the carb looking into the throt of the carb is the mixture adjust screwx Nest to that is another hole from which the gas is squirting. At highe RPMS it stops.

 

[pdehardon]

Re: Wont Idle 1987 merc 45hp

I removed the screw from which the gas was comming I replaced it with a screw of the same size that does not have a wole in it. This has stopped the gas leakage but the motor still wont idle.

 

[eurolarva]

Re: Wont Idle 1987 merc 45hp

It sounds like you need to rebuild the carb that is leaking. What is happening is that old gas was left in carb and you either have water, varnish or gum problems with that carb. Get a rebuild kit. Take carb apart and spray it down with carb cleaner or soak it in clean gas over night. Go through the small holes with a thin piece of wire and blow out holes with compressed air (If using a compressor use under 30 PSI). Install rebuild kit and reset float. Put carb back on and do the mixture adjustment procedure outlined in manual

 

[KCLOST]

Re: Wont Idle 1987 merc 45hp

Yep, it's rebuild time on the carbs (both of them)... Get the manual and follow the instructions.. You'll be fine and out fishing...<br /><br />Let us know....

 

[pdehardon]

Re: Wont Idle 1987 merc 45hp

I have found the rebuild kits. Can you tell me which manual will cover the rebuild? Also where can I order it.<br /><br />Thanks for all the help. Its great to have some knowledgeable backup.

 

[eurolarva]

Re: Wont Idle 1987 merc 45hp

Iboats sells them. Here is a link syloc manual

 

[pdehardon]

Re: Wont Idle 1987 merc 45hp

The problem is now clear. The float in the bad carb is full of fule. This means it would not float and explains the fule squirting from the carb.<br /><br />In hind-sight I now realize that the carbs did not need rebuilding as they were very clean inside and the gaskets are new. Unfoturnetly I took the float bowl off the bad carb AFTER I disasembled the good carb and the pump section of the bad carb.

 

[eurolarva]

Re: Wont Idle 1987 merc 45hp

When you take carbs apart it is good to have the rebuild kit. Sometimes the gaskets will get torn or you find something wrong and you can fix it instead of leaving it apart for a week and then wonder how to put it back together again. Not sure if this is your carb but here is a link for that float. If it looks right you should be able to get it from your local merc dealer 45 HP Carb

 

[pdehardon]

Re: Wont Idle 1987 merc 45hp

Thanks Euro. I have bought the service manual. I should be fine to rebuild. <br /><br />However everyone should learn from my mistakes. I was cleaning the parts with an old tooth brush and didnt notice that the throtle and choke return springs has stick in the bristles until I banged the tooth brush on the rail of my deck and cought a glimpse of the springs tumbling into my garden.<br /><br />I have been able to fashion new springs from parts from Home Depot.