Mercury 50 hp brown-band 1984

[Timbo007]

My merc starts fine and sounds fine, but for the first ten - fifteen minutes of operation has a lack of power and top end rpm. After ten - fifteen mins it will suddenly pick up in rpm and power and generally behave for the rest of the day. I thought of replacing the check valves, but I'm only guessing. Any ideas ??

 

[achris]

Re: Mercury 50 hp brown-band 1984

Hi Timbo,<br /><br />Before you go out next time, pull the plugs out and have a look at them. You may see the bottom one is rusty a bit. If it is, then you have a leaky bottom seal. If not, start looking elsewhere.<br /><br />Chris.............

 

[Laddies]

Re: Mercury 50 hp brown-band 1984

Ussally when a engine does that the switch box is going away

 

[Timbo007]

Re: Mercury 50 hp brown-band 1984

Cheers for the ideas.<br />Though not very old, the spark plugs show no sign<br />of rust. I did notice the plugs are NGK BUHW but <br />should be BUHW-2. Would this make any diff ?<br />Can the switch box be tested or is this a case of replace and see what happens ? Not cheap at a guess !

 

[Laddies]

Re: Mercury 50 hp brown-band 1984

If you establish that the problem is spark related, it can be tested quite simple with a DVM

 

[Tim Fawcett]

Re: Mercury 50 hp brown-band 1984

I have a merc 50hp brown band as well serial number 4143563 - I have almost the same problem. I changed the plugs and it went away immediately but then returned again. do these engines oil up very easily if not running near to flat out most of the time? -. I use the boat a lot on a speed restricted river where I do short bursts when the river cops aren't around.
also my serial number shows it's a 1975 according to one website - can that be correct if yours is an '84?.
The plugs i tried were NGK BP8H-N-10. Again difficult to acertain if the correct ones or whether perhaps a plug that runs ok at low engine speeds would help me any one know of a more suitable plug for slow running???
Tim Fawcett

 

[Tim Fawcett]

Re: Mercury 50 hp brown-band 1984

anyone any ideas on how to stop plugs oiling up with slow running?

 

[Derric]

Re: Mercury 50 hp brown-band 1984

maybe change the pitch on your prop so you are bringing the engine RPM up but staying at the speed you want to keep from fouling your plugs. Or, maybe you have the wrong jets for your altitude? Good Luck!