1979 80HP Mercury carbie problems

[Sam/HainesHunter]

Hey all,
I have a '79 Merc 80hp thats giving me a real headache. So the issue is this brought the motor after it had just had a full overhaul. it sat in the garage for about 12 months while the boat repairs were done, installed the motor a few months ago and it ran great on the garden hose at home however when I took it for its first run it was great until I turned it off for about an hour. when I went to take it for another run it would idle but stalled as soon as it got a bit of throttle in gear. I noticed the bottom carbie was dribbling fuel from the little jet. I removed the carbies and cleaned them both also replaced the needle and seat in both. again it ran great on the hose at home no fuel dribbling out seemed fine. I took it for another run same thing again, after running around for about 30 mins turned it off sat for about 3 hours went to run it again, idled ok but stalled under throttle again checked carbie peeing fuel out the jet again has anyone ever encounted this before or know what the issue might be? Thanks in advance

 

[Chris1956]

Re: 1979 80HP Mercury carbie problems

Obviously the inlet needles are not sealing properly, even though they were replaced. If you have original floats (foam), they tend to disolve in the ethenol gasoline we have now. Of you have the hard plastic floats, they tend to crack.

I would replace the floats, and see what happens.

 

[Sam/HainesHunter]

Re: 1979 80HP Mercury carbie problems

Thanks, I thought it may have been the float and I went to the local Merc dealer here and he tried to tell me that they were $90 au each! seems exessive for a float. The ones in there are the foam type. I tried to have a look on this site for the floats but the carbie parts for my year model are not shown. Also I got a bit scared of by the dealer as he was saying how you have to set the float heights and I have no idea what the heights needs to be, Do i need a manual for the details or is it a simple thing to do? I have rebuilt auto carbies before but this is the first o/b I have owned.

 

[carholme]

Re: 1979 80HP Mercury carbie problems

Sam;

As it looks like you have a four cylinder, take a look at this:

http://www.crowleymarine.com/mercury-outboard/parts/484_8.cfm

select "Carburetor" and see if this is your carb.

If you provide the s/n of your engine and we can show you the right parts list as well as the maintenance breakdown where you will see the float adjustments.

carholme

 

[Sam/HainesHunter]

Re: 1979 80HP Mercury carbie problems

Yep it is a four cyl, and thats the carbs. Ill check the serial number this arvo.

Cheers for the help. Ive been reading these forums for a while and its good to know there is people out there who are happy to help. Just wish some of the local suppliers round here could be as helpful!

 

[Chris1956]

Re: 1979 80HP Mercury carbie problems

Float height is simple to set. Invert the carb float bowl cover. Bend the middle of the lower lever until the upper lever is parallel with the carb cover. Now turn the bowl cover right side up. Measure between the two levers at their ends. The measurement should be 1/4". Bend the upper lever to drop or raise more to make it so.

Any service manual will have this with pictures.

 

[Sam/HainesHunter]

Re: 1979 80HP Mercury carbie problems

So I checked the serial number last night it is 8061798. It would definetly be an advantage to see how to do this with a service manual.

anyone know if there is a PDF version that could be downloaded? I have searched the net but cannot find a free copy anywhere, am I being a tight arse should I just buy one?

 

[Mi duckdown]

Re: 1979 80HP Mercury carbie problems

Yes. OEM Merc Manual. Try ebay.Have serial number???

 

[carholme]

Re: 1979 80HP Mercury carbie problems

Sam;

I have just sent you a PM. Can you check and advise?

Regards
carholme

 

[Sam/HainesHunter]

Re: 1979 80HP Mercury carbie problems

Carholme,
As per pm have a look at this.



is 0.690
0.665
In inches? if so are the two numbers the min/max?

Regards
Sam

 

[carholme]

Re: 1979 80HP Mercury carbie problems

Sam;

As it appears to be in a Quicksilver package they should be inches and yes they are min/max, the difference being .025".

carholme

 

[Sam/HainesHunter]

Re: 1979 80HP Mercury carbie problems

So I checked the float heights on both carbs last night and the bottom carb was 17mm (0.669) and the top 17.3mm (0.681) which I believe is within tolerance. Any other ideas what could be causing this problem? What confuses me is that when I first put it in the water in runs fine however after I turn it off and let it sit for an hour or so it will only just idle and bogs down and stalls under any throttle, if I remove the air box I can see the fuel dribbling out of the bottom jet and pooling in the bottom of the cowling.
This sucks I just want to take the young fella on his first reef fish!!!!

 

[carholme]

Re: 1979 80HP Mercury carbie problems

Sam;

If you want to verify the carbs, swap them and see if you still have the leakage in the same carb. Then at least you have the problem zeroed in to that carb.

If you think you have everything else covered, have you tried the synch procedure here:

http://forums.iboats.com/showthread.php?t=168855

carholme

 

[Faztbullet]

Re: 1979 80HP Mercury carbie problems

Hey Sam... what you are describing is signs of a porous float. After it runs it gets heavy from fuel saturation and float level changes. When you tear it apart it drys out and then acts ok until its ran again. If you have the foam floats replace them, this is a have to with todays fuels. You can get the floats here at iBoats under part #18-7249 and it comes with inlet nedle also for around $18 USD each...

 

[Sam/HainesHunter]

Re: 1979 80HP Mercury carbie problems

Thanks guys, the porous float thing sounds exactly like whats going on, I couldnt work out why after sitting for a couple of days it would run perfectly again....
Im picking up two float kits tomorrow morning so hopefully over the weekend I can get the carbs rebuilt.
Fingers crossed.

Thanks so much again guys for your help.