1991 50hp Mercury questions?

gpfishingdude

Chief Petty Officer
Joined
May 1, 2012
Messages
538
We just bought a pontoon boat that has a 91 50hp Merc on it. The guy let me start it on the muffs and it ran great but the idle was set pretty high. Is there a knob that you adjust to turn the idle speed down? It has the Quick Silver controls mounted on the side of the railing next to the console. I have no idea how fast an old 50 horse Merc. burns fuel. I think the plastic fuel tank is probably a six gallon one. Anybody know how long six gallons would last at cruising speed?
 

Barnacle_Bill

Admiral
Joined
Feb 8, 2004
Messages
6,469
Re: 1991 50hp Mercury questions?

Idle on most outboards is done thru a procedure called link & sync. I highly recommend you get a manual to do it right. OEM manuals are by far the best but cost a lot more.
 

gpfishingdude

Chief Petty Officer
Joined
May 1, 2012
Messages
538
Re: 1991 50hp Mercury questions?

Thank you! Maybe I can find out by looking at the manual for my 25 HP Mercury because it is an old electric start too. I haven't had this boat and motor long enough to get a manual for it yet. I just thought that it might be a good idea to turn the idle down a little to make sure it doesn't slam into gear when a I shift it.
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
Re: 1991 50hp Mercury questions?

The motor will idle slower when you put it in the water.
They run fast on the garden hose.

Try it before you mess with it.


6 gallon tank will last between 1 and 5 hours, depending on what you mean by cruising speed. Best to take a spare tank along until you know what to expect.
 

gpfishingdude

Chief Petty Officer
Joined
May 1, 2012
Messages
538
Re: 1991 50hp Mercury questions?

Thank you so much! I will try to get it in the water early next week. I try to give the working people the weekends. My neighbor has a spare tank he offered to give to me. I will take it along. We just bought the boat Thursday and I had too many things I had to do to make it legal to get it in the water this week. If everything looks good I will probably buy a 12 gallon tank right away.
 

gpfishingdude

Chief Petty Officer
Joined
May 1, 2012
Messages
538
Re: 1991 50hp Mercury questions?

I found out that the idle was just fine like you said. We had it on small fishing lakes and could only open it up for a few minutes at a time. I doubt if the total running time was over an hour including idling. We started with 3/4 of a 6 gallon tank and had a third of a tank left. I bought the 12 gallon tank and installed it. One thing I have found out about this motor is that it floods very easily. Once it has been ran don't squeeze the fuel line bulb or choke it and it will start in a fraction of a second and run like a top. After I fill the new tank I plan on cold starting it once to get fuel through the line and after that just turn the key and let it start.
 
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