1975 Mercury 500 outboard

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Thornsburg

Recruit
Joined
May 26, 2012
Messages
2
My Merc will rev up fast in neutral, but when put in gear, it dies...what is going on with it? I am no boat man, in fact this is my first. Any help would be appreciated, as this engine has cost me over $300 already in work. Sad thing is I have seen this motor in action on You-tube and was excited to own it.
 
K

kazek

Petty Officer 2nd Class
Joined
May 14, 2011
Messages
193
Re: 1975 Mercury 500 outboard

hmm.first thing...how high are you rev'n this engine.around 1000 rpms is normal.check fuel delivery system
 
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oldman570

Lieutenant Commander
Joined
Mar 25, 2011
Messages
1,615
Re: 1975 Mercury 500 outboard

Are you reving the motor on muffs, on the water, or in a tank? Motors on muffs should never be reved more than a fast idle (1700RPM) as there is no backpressure on the exhaust and the motor could be damaged. All carb settings and final tuneup needs to be done in the water or a test tank. Doing the settings on muffs will get it to run so you can do the fineal. Try adjusting the idle jets out 1/8 to 1/4 turn and see if it helps. Lean carb settings will cause the motor to burn a piston and be junk or alot more work. May be a pain doing things correct the first time, but will save $$$ in the long run.
Oldman570
 
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Thornsburg

Recruit
Joined
May 26, 2012
Messages
2
Re: 1975 Mercury 500 outboard

This boat has only been run by me, in the water. I have had the local boat mechanic work on it, which, as stated, he got the motor running like a champ in nuetral, however, when it is put into gear, it will either idle only, or kill over, as if choked out. It also takes choking the motor every time to restart it. I would never try to run the boat out of water, as I have not the experience to do so and prefer not to unintentionally break anything.
 
Faztbullet

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,938
Re: 1975 Mercury 500 outboard

Pull the lower spark plug and see if it has water drops on it as it sounds like the lower crankseals are out on it. They will run great on a hose with bad seals.
 
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