1991 Merc 75 Hp Will Only Run With Choke On ??

S

steve lee

Cadet
Joined
Apr 20, 2009
Messages
19
It Will Bogg Down And Die

Hold The Choke Down Dont Let Go And Runs And Will Plane Out

Its A 1991 Mercury 75 Hp

Bad Idle Missing Give It Little Gas And Will Die But Not With Coke On ???

Whats Wrong
 
tashasdaddy

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 1991 Merc 75 Hp Will Only Run With Choke On ??

contaminated carbs, clean and rebuild.
 
E

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: 1991 Merc 75 Hp Will Only Run With Choke On ??

Better check the fuel pump, too. See the recent post regarding Mercury TSB's, specifically the link within that thread for the Merc TSB on fuel starvation.

I just finished up a 115-4 Merc in which the fuel pump check valves looked like wadded-up lumps of paper from ethanol-fuel degradation.

If your fuel pump has never been rebuilt, it very likely needs the upgraded alcohol-resistant components anyway.

Note that, depending on the model, there are (2) different styles of fuel pump repair kits. One is for the pump which has a 90-deg check valve coming right out of the pump cover. The other kit is for the type of pump with a separate, inline check valve. So be sure to get the one which matches your motor!

HTH........ed
 
S

sportsmanphil

Petty Officer 1st Class
Joined
Mar 8, 2009
Messages
257
Re: 1991 Merc 75 Hp Will Only Run With Choke On ??

Ive done some research on fuel vs. outboard's

E-85 is a NO NO for any outboard according to each of the manufacturers.

All say that 10% Ethanol is OK but not really reccomended.

Most say to stay away from 10% methanol.

That TSB blames Ethanol/methanol on the check valve damage

*******

I wondered if some of my problems was due to fuel. All the gas stations around me have stickers on the pumps that say "may contain up to 10% Ethanol" So I have no clue if I am getting Gasoline or 10% Ethanol. The people inside are clueless.


Here is a question for anyone in the know. Stations with 10% ethanol, do all grades have this or just 87?
 
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