1987 50HP Mercury problem

[Red Ticket]

I bought a motor that had been sitting for a couple of years. Before I started it, I pulled the carbs & cleaned them. The motor always starts easily. Here is the problem. When the engine is cool, it powers up like it is only getting partial gas, but runs smooth at 1/2 power. Then as it warms, it starts cutting (sputters)into full power. After it is warmed up, it runs great, with no problems at all. I am trying to figure out if this is a fuel problem, or an electrical problem. It takes about 5 minutes of running before it sputters to full power, and about a half an hour before it smooths out and runs fine at full power. I'm hoping this is a classical symptom for a Mercury problem that everyone knows but me!
Any ideas? Thanks in advance...

 

[Red Ticket]

Re: 1987 50HP Mercury problem

I just found out this is a 1980-81 motor. Serial #5533556 It has very few hours on it. Does anyone have an idea about this type of problem?

 

[jackd1023]

Re: 1987 50HP Mercury problem

I had this on my 115, I installed hotter plugs and ran some seafoam and viola. May want to wait for a pro. Good luck

 

[coolguy147]

Re: 1987 50HP Mercury problem

does pumping the primer bulb solve this problem?

how your compression?

other idea is when the motor is cold for some strange reason its not sparking on all four cylinders. then warms up bang bang bang bang all four.

 

[Red Ticket]

Re: 1987 50HP Mercury problem

"other idea is when the motor is cold for some strange reason its not sparking on all four cylinders. then warms up bang bang bang bang all four."
This is exactly whats happening, but I can't figure out if it is in fact an electrical issue or a fuel delivery issue. Since it happens every time this way, I lean towards an electrical problem... But what?

 

[Red Ticket]

Re: 1987 50HP Mercury problem

"when the motor is cold for some strange reason its not sparking on all four cylinders. then warms up bang bang bang bang all four."

Does ANYONE have an idea what might cause this?

 

[Red Ticket]

Re: 1987 50HP Mercury problem

I know this may tick off the moderators on this site, but I have to ask....
Is there any other forums that you would recommend to post this problem on? I really need to get some ideas as to what the problem might be. Thanks to all...

 

[DuckOfDeath]

Re: 1987 50HP Mercury problem

Are you assuming you have no spark on one or more cylinders or did you actually test it? No one is going to be able to help you if you're unwilling or unable to do some basic troubleshooting. Without it, you'll only get speculation, which is worthless.


Check for spark on all cylinders and let us know which cylinders fail, if any. You should also do a compression test. You can buy both of those test items for under $40 at any autozone.

 

[Red Ticket]

Re: 1987 50HP Mercury problem

Thanks for your reply. Checking the spark when the motor is cold and acting up makes perfect sense. I'll do that as soon as the ice is off here. The compression, however, doesn't make any sense TO ME at all. Compression problems should affect the motor at all temperatures to some degree. This motor runs perfectly after it has warmed. And I do mean perfectly! Compression is an easy check, and I can do it, but I have no doubt it's fine. If the motor has spark when cold, however, then the problem must be in fuel delivery. Thanks for your input!

 

[DuckOfDeath]

Re: 1987 50HP Mercury problem

No problem. I agree that compression isn't likely to be your issue but it can't hurt to know where it stands seeing as you just bought the motor. I'm no prefessional, but I've read here enough times that you need to verify compression, spark, and fuel in the carbs before the real troubleshooting can begin.

If you find one not firing, swap that wire and coil for one that is and see if the problem follows.

 

[Noah George]

Re: 1987 50HP Mercury problem

Thanks for your reply. Checking the spark when the motor is cold and acting up makes perfect sense. I'll do that as soon as the ice is off here. The compression, however, doesn't make any sense TO ME at all. Compression problems should affect the motor at all temperatures to some degree. This motor runs perfectly after it has warmed. And I do mean perfectly! Compression is an easy check, and I can do it, but I have no doubt it's fine. If the motor has spark when cold, however, then the problem must be in fuel delivery. Thanks for your input!

Thats not so on your compression issue; Your rings expand when your engine is warm. That is why some engines smoke more when cold intil they warm up. If your engine is not running to 180 degrees in fresh water you are burning up your rings slowly. In salt water you don't want to run your engine over 160 or you will make salt crystals in your exaust. You may also have a head gasket cross firing a bit until it warms up.