1980 mercury 80 hp lower carb not sucking

[swarfmaker]

I just bought a 1980 80 hp mercury that was rebuilt a couple of years ago and I was told it ran fine. However it sat for about a year. When I run it it idles fine but dies when going into gear. I've checked compression and get 120 psi in all cylinders. It won't develop power at all. Here's the weird thing: I took it out on the lake last night and discovered that the lower carb is not sucking at all. You can close off the idle needle completely and it has no effect, nor when running with the butterfly valves open do I get any suction into that carb. If the reeds were bad I should get blowback out the carb but I don't. Any suggestions? Anyone who gives this a little think will be appreciated!

 

[Laddies]

Re: 1980 mercury 80 hp lower carb not sucking

Theres a very good chance the engine has a bad reed on 1 of the 2 bottom cyls. usually if you can nurse a engine with a bad reed up over 2000 RPMs it will pickup the 2 cyls it's missing on but in also could be a inlet stuck on the bottom carb I certainly would ck the carb first

 

[swarfmaker]

Re: 1980 mercury 80 hp lower carb not sucking

Wow that was quick! Thanks. Laddies, when you say inlet on the carb, what do you mean? When I'm looking at the engine running and the carb exposed, I can see right through the carb with the butterfly valve open. Regards.

 

[Laddies]

Re: 1980 mercury 80 hp lower carb not sucking

The carbs will have to be removed from the engine to do a proper cleaning but with care one can remove the top of the carb by removing the small bolt that holds the filter covers on (usually have to do both as the hose between the two is to short to remove one) 2 small screws hold the top of the carb on remove it, if there is not fuel any fuel in the bowl the inlet needle on the cover is stuck and should be replaced (some can be saved with a good cleaning) I would recommend a complete cleaning as if the high speed jet was completely plugged it could also be a problem. Heres a picture of a carb apart similar to yours to give you the position and names of the parts

 

[swarfmaker]

Re: 1980 mercury 80 hp lower carb not sucking

Thanks Laddies. I've done a little more troubleshooting and learning about this motor. It turns out that my bottom 2 cylinders are not firing. I checked the resistance between the trigger wires and they check out ok per the seloc manual, and the stator resistance looks ok too. Is there any thing else I can check before springing for a switchpack? Regards to all...

 

[CharlieB]

Re: 1980 mercury 80 hp lower carb not sucking

You really need to get ahold of a DVA meter to properly test stator and triggers. An ohms meter is a good indicator but it is not the final determinant, we've seen many component ohms test acceptably yet fail to produce under load.

No return on electrical parts.

It very well may be a bad switchbox but I really would prefer you prove your trigger good/bad before you spend any money.

 

[fishdog4449]

Re: 1980 mercury 80 hp lower carb not sucking

my 80 had the same problem not firing on two bottom clyinders would stall when going into gear, turns out it was the coil(inside the flywheel) that supplies power to the two bottom cylinders. both clyinders would kick in at about 2000RPM and it would run real smooth
I had the shop pull the flywheel for me, then I put in a new coil and stator and put the wheel back on
idles a whole LOT smoother and better acceleration

 

[Yepblaze]

Re: 1980 mercury 80 hp lower carb not sucking

I am not trying to be mean.

If your carb is not sucking, how could it be an ignition failure that has caused it?

I think you need professional help, beyond what can be had here with your operational, and diagnostic references.