1988 Mercury, 20HP, Pull Start, Tiller - Will not Start...

[HVACRat]

This is my first Mercury outboard, she is a 1988 20HP, tiller steer pull start engine. I bought this engine about a year ago and she has ran like a champ until now.

About a month ago I got off in some water I shouldn't have been and bent my prop shaft; I replaced the prop shaft (which was very easy by the way!) but now I have another problem.

This weekend I put her in at the ramp and she didn't start on the second or third pull; this has never happened so I knew something was up. What I found was one of the two wires that come from the stator to the power pack had ended up against the exhaust housing and melted the insulation causing a short. I cleared the short but still had no joy.

I called my boat guy and he said it was either the power pack (shorted) or the stator (shorted). Since I was 'on the water' (this was during our Extreme Hunt!) all weekend he ordered the power pack, I received it Friday and installed it... Still will not run.

I am going to pull the flywheel and check the stator next, at home now, and see if I can make heads or tails of this.

What I really need to know though is the basic sequence of operation. I am getting fuel and spark to the plugs/cylinders but she will not start...
Spark is made in the stator, then...
Spark goes to the power pack, but I don't know what happens in there...
Spark THEN goes to the coils, again, I don't know why...
Spark THEN goes to the plugs.

The question is what do all these components do along the ignition sequence?
What is the best manual for this engine? A friend says Clymer is very good but I also want to know if I can get a 'factory' manual that is model specific; and if so where?

Any thoughts on my ignition problem will be greatly appreciated until I can get my hands on the correct manual.

BTW, I LOVE this motor; it fits my hull perfectly, the grip shift is GREAT and until this little problem (which I should have noticed a wire out of place against the exhaust housing!) has never left me in doubt about getting home.

 

[HVACRat]

Re: 1988 Mercury, 20HP, Pull Start, Tiller - Will not Start...

Performed a compression test last night...
One pull of the rope = 105 PSIG
Three pulls of the rope = 125 PSIG
Same on both cylinders.

I am pulling the flywheel tonight.

 

[Lubosleftboot]

Re: 1988 Mercury, 20HP, Pull Start, Tiller - Will not Start...

If you are getting a spark there is nothing wrong with either the stator or the powerpack... A common fault on outboards is a sheered woodruff key and if thats the case your motor will not start as the timing will be way off.

When you remove the flywheel you will be able to see if this is indeed the case.

LLB

 

[HVACRat]

Re: 1988 Mercury, 20HP, Pull Start, Tiller - Will not Start...

7hanks, I will check it tonight; my repair manual should also be in today.

 

[HVACRat]

Re: 1988 Mercury, 20HP, Pull Start, Tiller - Will not Start...

Okay, I got her figured out last night.
After talking to my local boat repair guru he told me to try new plugs and a *small* shot of ether before I removed the flywheel. So, on the way home I picked up my repair manual and a couple of new plugs; finding the right plugs was a lesson in frustration...

Anyway, got the new plugs in, shot a *short* burst of ether into the carb and... she fired right off!

I pulled and disassembled the carb. I found that the fuel inlet needle had stuck in the closed position and was not allowing fuel into the bowl of the carb; I had to use needle nose pliers to remove the inlet needle. I gave everything a good shot of carb cleaner, reassembled and installed the carb, pumped the bulb, choked and she started right off on the second pull!

I left the new power pack on as the old one definitely had a melted wire, did some further cleaning while I had the parts off the power head then put her all back together. I ran her in the tub for a good hour in forward, reverse and neutral and she performed well.

I am going to get a carb gasket kit, fuel pump diaphragm and fuel filter and put them on this weekend.

I have never had a carb 'gum up' before due to sitting fuel; however, she sat all summer long last year without use due to my busy work schedule. She is usually ran at least a couple of times a month, if not more; so I will be using Seafoam fuel treatment in my fuel from now on to keep this from happening again once I get her cleaned up proper.

Thanks for the help.