Help Mercury 90 hp won't start

S

Singing Boat Guy

Seaman Apprentice
Joined
Jul 22, 2007
Messages
47
Hello Everyone,

I just purchased a 79 16 foot glasply with a 78 mercury 90 hp 3 cyl 2 stroke (serial # 5714660) on it. The boat was disassembled and in mid project when I got it, so I kinda working at it by the seat of my pants. The biggest problem I am having at this moment is I can't get the motor to run. It cranks over and will sometimes catch briefly, then die. It is getting gas, but strangely it is leaking from the carbs, the bottom one mainly, and then pools and comes out the bottom cover. Is this normal? I know I have been working it trying to start it.

I bought a new 650 cranking amp battery for it, but wonder if this is enough battery for the motor? I have checked that it is getting spark to the plugs, have pulled 5 of the 6 plugs to clean them up.

The weirdest thing about trying to start it is that mostly it only allows you to spin it quickly before it shuts down the ignition on its own, so the key is still turned and held in start. Sometime it will let you really crank her, then it shut it down. Is this somekind of safety feature so you don't burn out the starter?

I would appreciate any help and ideas that anyone has.

Thanks in advance,
Chris
 
S

Singing Boat Guy

Seaman Apprentice
Joined
Jul 22, 2007
Messages
47
Re: Help Mercury 90 hp won't start

Thanks for the reply Plainsman! I will get a volt meter and start checking some of that stuff. It is almost like it is not getting gas, yet it was dripping out of the bottom carb. I will try it again tomorrow as I am sure it got flooded. ( I hope that is why)
 
C

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,073
Re: Help Mercury 90 hp won't start

Chris, In 1978 the Merc 90HP motors were inline sixes with three carbs. They also had a distributor. If your carbs are leaking fuel when the motor is in the upright (running) position, your carb floats are set incorectly, the inlet needle and seat are leaking or your floats are defective. On that model, the original floats were made of hard foam. The replacement floats were made of hard plastic. Each float had a small spring on the top which pushed on the compound lever to close the inlet needle.

Sounds like your carbs to me, but check to see that you have spark on all cylinders, and no arcing to ground is occuring.
 
S

Singing Boat Guy

Seaman Apprentice
Joined
Jul 22, 2007
Messages
47
Re: Help Mercury 90 hp won't start

Chris1956, thanks for that tip. This is getting into some really unkown territory for me, as I have never done anything with carbs before. What is arcing to ground and how can I check for it? I am familiar with checking plugs and wires for spark, just never even heard the term arcing to ground before.

Thanks for the help.
Chris
 
S

Singing Boat Guy

Seaman Apprentice
Joined
Jul 22, 2007
Messages
47
Re: Help Mercury 90 hp prop won't spin

Re: Help Mercury 90 hp prop won't spin

Okay got the motor running. It turned out to be the ignition switch. Now it runs, but I can't get it to go into gear, neither forward or reverse. I am going to guess that it is in the controller. As mentioned above I am putting this boat back together, as it was all apart when I bought it. I put the throttle cables into their correct places I hope. There are two wires that come off the front of the controller out of a seperate harness that is marked trim, tach and something else. There are only two wires that can be attached to anything, as the others fold back to the controller. What do these connect to and do they have to be connected?

I am almost ready to put it in the water and try it out.. Please help.,


Thanks,
Chris
 
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