1982 mercury 800 80hp 4cyl float level

joshgar8

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Aug 6, 2012
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I have a 4cyl 80hp that's giving me problems and I think I may have issues with both carbs float levels. Can you guys describe how to set the float level exactly? I measured from the bowl gasket flange on the carb (beside the float) to the most upper part of the float when the carb is upside down and it's roughly 13/16". I have read that this measurement needs to 11/16". I have also read that if you measure from the same flange to the float on the most outer part of the float assembly (main air intake side of float) it should be 7/16". Another technique I was told was to make the floats level when the carb was turned upside down. The floats was set fairly level when I tore them apart but for them to be level it isn't close to either of the two measurements causing the fuel level in the bowls to be lower.

I do have very detailed pictures of these carbs with the floats measurements but cannot seem to add them to the post.

Thanks in advance for your help,
Josh
 

James R

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Re: 1982 mercury 800 80hp 4cyl float level

What are the symptoms and what have you done to the carbs?
 

joshgar8

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Re: 1982 mercury 800 80hp 4cyl float level

I rebuilt the carbs with all new gaskets and verified all ports was clear. I am not an expert on adjusting float heights on this or any other carb for that matter so I left the heights where they was when I acquired the boat/ engine. I rebuilt the fuel pump, replaced the fuel filter, replace the faulty primer bulb and made sure all plumbing to the carbs was tight and leak free. I set both the initial timing and max timing as per factory specs. The idle mixture screws was set at 2 1/8 turns out.


I took it to the lake with all the above done and here are the results:
Very very hard to start on initial startup, almost as if there is no choke at all. After it was running and warm I took it out of the no wake and it ran halfway decent. Sick but halfway decent. I came back and picked up another person and the added load prohibited it from building rpm and coming out of the hole. I hit the choke, which on this engine is actually a enrichment circuit to dump more fuel from what I understand, and it built the rpm and came out of the hole and made it up on plane. I thought I may have had a lean condition resulting from the mixture screws so I adjusted them. I went everywhere from 1 3/4-3 3/4 turns out without any real change. I could get it to react any different other than picking up rpm and getting out of the hole when the choke was applied. Without the choke it would only turn about 3,000 rpm max. I do think there are issues with the floats/needle and seats because on my other bigger inlines I can over power the seats with heavy heavy pressure on the bulb to force fuel into the main body of the carb to ease startup on the initial startup, this one you cannot. An elephant could stand on the bulb and it wouldnt blow by the needle and seat to help on cold starts.

The venturies in the carbs have seen better days. Somebody hit them with a hot dose of cleaner and melted them. I have two new ones ordered.
 

joshgar8

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Aug 6, 2012
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Re: 1982 mercury 800 80hp 4cyl float level

Gerry,

Thanks allot for the link. I was measuring from the right location on the bowl flange to the right location on the float and that verified my fuel level is approx .150" low in the bowl on both carbs. I am going to correct that and replace the venturi's and see what we have. I had to order the venturi's from two different locations so it will be the middle of the week before I can report the results.

Again, thanks allot for posting the manual on the host site and linking me to it.

Josh
 

James R

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Feb 1, 2007
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2,660
Re: 1982 mercury 800 80hp 4cyl float level

Your symptoms do indicate a fuel flow problem. Does the primer bulb go hard when you pump it. If it does and considering your symptoms, you may have a restriction between the bulb and the carbs. The fact that you get an increase in RPM when enrichener is applied definitely indicates a fuel shortage. Does the bulb go soft when you run the motor. I think I would consider checking the fuel pump assembly.
 
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joshgar8

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Aug 6, 2012
Messages
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Re: 1982 mercury 800 80hp 4cyl float level

James,

The bulb gets hard as it should after pumping it. While running the engine it doesn't stay hard as it does just before starting it but only requires maybe half a pump to get back to the prestart condition. I replaced the fuel pump diaphragm and the filter along with the strainer screen in the pump.

Thanks for your info. I am going to give it another try after the new venturi's get here. The others are in so bad condition I think they are affecting the fuel draw out of the bowls. That in combination with the float adjustment I think could be tributing to the problem.

Thank,
Josh
 

joshgar8

Seaman
Joined
Aug 6, 2012
Messages
65
Re: 1982 mercury 800 80hp 4cyl float level

I got the venturi's in the mail today and installed and float levels reset. I adjusted the idle mixtures screws to 2 turns out as a base setting and plan on trying it out in the next couple days. Hopefully I am in the ballpark.
 

joshgar8

Seaman
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Aug 6, 2012
Messages
65
Re: 1982 mercury 800 80hp 4cyl float level

I was finally able to take the boat out for a test today. The float level adjustment solved the issue that required holding the choke to get the boat to come out of the hole but I think I have many more issues.

I unloaded the boat with both carb idle mixture screws 2 turns out as a base setting. I backed it down the ramp and hit the key and it fired right up. I backed off the trailer and idled over to the dock. There was very slight signs of it loading up. I idled out of the no wake and punched it and it took and ran like a sewing machine. I ran maybe a mile WOT @ 5450 RPMs and shut it down. I wanted to see how it would idle and how it would run after idling like docking and unloading and loading at the ramp ect. After idling in gear alittle ways I went to attempt to get it to come out of the hole and it fell on it's face and died. Acted like it was loaded up. I adjusted the idle mixture screws to 1 7/8 out and ran it. It seemed to improve the loading up on idle but hurt the top end. It would only turn 4900 RPMs. I then thought I went the wrong way and adjusted it to 2 1/8 turn out on both and tried it. It helped the top end (got it back to wot) but made for more issues loading up. The only way to get it to run after a loading up spell was to bring the fast idle up until it smoothed out and sounded decent and then try it. Usually that helped.

Another issue I'm very concerned about is a slight rattle in the engine. It only does it when it's cold and or under acceleration. Is is not a consistant rattle like a rod knock and it normally goes away or gets less noticeable after it's ran sometime. It does it both in gear and out. Today it was in neutral and started rattling and I noticed when the rattle started the rpm decreased by about 200 rpm. I shut it down and loaded it up. My frustration got the best of me. I am about ready to get rid of this crazy thing or take it to somebody else that can fix it.

Any ideas guys? I'm losing hope real fast in this thing!

Thanks in advance.
 
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