1972 Mercury 800 80 Hp

[kjburr08]

The motor is a 1972 Merc 80hp 800 4 cylinder 2 stroke.

I have a problem cold starting it. It takes a lot of cranking to get it to fire. If I spray starter fluid or something like that into the carbs it usually fires right up. Other than that it just cranks and cranks. What could be going on here?

Does anyone know if this motor has a water pump of some sort?

 

[Chris1956]

Re: 1972 Mercury 800 80 Hp

Those motors are hard to start when cold. Take a compression test. If all 4 cylinders are 100PSI+, you are good to go. The best way to start 'em is to pump up the primer bulb until hard. Now force a bit more fuel into the carbs. Make sure the motor is all the way tilted down, and the choke plates are all the way closed. Put the cold start lever all the way up and crank it.

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp

well all 4 cylinders are getting about 130psi. i pumped the bulb, threw the throttle forward, held the choke down, and tried starting it. It just does not want to start without starting fluid or something in the carbs. do the carbs need rebuilding? I know one of the plates was not pushing closed. after about an hour playing with the carb plate it finally is working somewhat correctly. it seems its still not wanting to run though. after trying and trying to start the motor is just is not wanting to fire up period. it seems its not getting gas but i just dont understand why. what happens when you run these out of water for a few minutes, not in gear though?

 

[gator1959]

Re: 1972 Mercury 800 80 Hp

they get hot out of water,and your water pump impeller is likely not in good shape,but if it was still running when you shut it down,that shouldn't affect it's ability to start right up now.

 

[Chris1956]

Re: 1972 Mercury 800 80 Hp

It is quite possible that the carb idle circuits are gummed up. Possibly the float heights are out of adjustment as well. You might pick up some inlet needles and gasket sets for the carbs and rebuild them. A service manual is very handy as well.

There is a rubber impeller in the lower unit that pumps the cooling water. Running the motor w/o source of cooling water will burn it up pretty quick. Pick up a flusher device for it. They are under $8 or so.

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp

well i think i got the float and the needle and seat to free up. there was a crack in the float but it still goes up and down as its supposed to. also the needle and seat was stuck i got them freed and not gas is flowing to the bottom carb as it should. well i find out i am not getting spark. I took the distributer cap off and the button to the coil wire was broke! I think chunks of the button were still letting the engine fire but not as it should. I am going to get another distributer cap and see if she starts/ Thanks for all the help and does anyone know a good place for older merc boat parts, i will search ebay.

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp

heres what i need but its $134!!!

http://cgi.ebay.com/ebaymotors/New-...8096085QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

 

[mark_gober]

Re: 1972 Mercury 800 80 Hp

KJ,

Now I'll preface my post by saying that I only have a small 18hp Merc, but on my motor, when I pull the choke on it, it has a lever that pumps a small diaphragm and shoots a small shot of fuel into the carb. If yours doesn't want to start with just choke, but starts right up with starter fluid, you may not be getting that shot of fuel. When i rebuilt my carb, my diaphragm was completely disintegrated. New one was nice and pretty and pumps perfectly.

BTW, I would certainly address your cracked float. Mine had a microscopic pin hole and got flooded. It is a modern marvel. I removed the float weeks ago and replaced it. To this day it still has fuel it. How did the fuel get in there, but can't get out? The float was dirt cheap from a local supplier. I think I gave $6 for it.

Mark

 

[Chris1956]

Re: 1972 Mercury 800 80 Hp

There is no accelerator pump on that Merc 800. Replace the float if it has cracks.

The dissy caps are expensive as you have found out. Also, the rotors are non-replaceable, so don't try or you will need a new dissy shaft. The carbon center electrode in the cap is replaceable for $3-4.

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp

thanks for the advice guys. Do you know where I can get the carbon center electrode for it? That sounds like a better route than spending up the yang when i have a decent cap after all. I will check around in the meantime. I'll also try finding a new float for it..

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp

Well I found a float, but I cant find the carbon electrode you mentioned. I have a feeling if I called a mercury dealer they would probably not know what I am talking about.

 

[Chris1956]

Re: 1972 Mercury 800 80 Hp

You can look up all your parts on the Crowleymarine.com website or the dougrussell.com web site. You can order it from them or from a Merc Dealer

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp

Well I think I might have found it. http://www.crowleymarine.com/mercury_parts/445/40.cfm

do you think it is #36? also known as a brush kit. or do you think its something else?

 

[Chris1956]

Re: 1972 Mercury 800 80 Hp

That appears to be it. I think a Merc Parts Dealer would also know what it is. I bought one for my '77 Merc a few years ago. It was in stock at my local dealer.