1979 Mercury 80 hp puking out...

[jasunderland]

When I try to take off, If i go push the throttle down slow, it pukes out and dies at about 1/2 to 3/4 throttle. If I hammer it down fast and hard, it gets up and goes.

Any ideas?

4 cylinder 2 stroke. just changed plugs.

 

[jasunderland]

Re: 1979 Mercury 80 hp puking out...

Any thoughts?

 

[Jeff Lindquist]

Re: 1979 Mercury 80 hp puking out...

i have an '82, 80hp mariner 4 cylinder 2 stroke did the exact same thing. after rebuilding carbs, i inspected wiring closely. white wire from trigger to switchbox had cracked insulation, was exposed wiring and so on. cut it farther back and spliced in new section. also, switchbox to coils had about 4 wires in the same condition, so i replaced all 8 (4 to coils, 4 grounds) between switchbox and coils. then i was getting way better spark. polish and clean any electrical end you take off, or all if you get on a good run. also adjusted throttle arm and spark advance a little to smooth idle. gonna lake test this weekend and fine tune. hasn't run for 2 years because of the same problem you got so i figured if it doesn't run now, whats the worst that could happen if i take a crack at it, between the manual and this forum. driveway test with muffs is better than it has ever run at this point.

 

[jasunderland]

Re: 1979 Mercury 80 hp puking out...

Thanks for the advice. I will check all the wirering as it has sat for a while and there is probably some good dry rot going on!

 

[Jeff Lindquist]

Re: 1979 Mercury 80 hp puking out...

keep me posted and i will try to pass on any limited knowledge i have on my similiar motor. not sure if i can lake test this weekend now. 3 days of rain forecast. good luck!

 

[jasunderland]

Re: 1979 Mercury 80 hp puking out...

Well I talked to my old man who owned the boat before me and he said he thought that it had the same problem a while ago and there was a seal that was causing a leak in the vacuum. I am going to replace the o ring that is between the fuel line and fuel filter.

But the biggest thing that i noticed when I opened it up and looked closely was what you were talking about. I counted 5 wires that need replacing and one that looks like is one of the main hot wires(its looks like 10 or 8 gauge wire). When I poked at that one and saw the cover was cracked, it picked at it and the whole wire fell apart!!
Here are a couple pics:

I think it was good thing I found them now as about one more big wave might have caused me some terrible problems in the middle of the lake!:facepalm:

 

[Jeff Lindquist]

Re: 1979 Mercury 80 hp puking out...

That sounds exactly like what i found. I did get on the water and after about 20 minutes of setting up the throttle arm and spark advance arm, mine is running better than i have ever seen it. Good connections and the wiring like what you discovered were the main problem I'm sure. I was cutting figure 8's at about 35-40 mph yesterday. I noticed a little stickiness in the the throttle cable after sitting so long though. Maybe sheck there as well and make sure you are getting responsive cables at the motor end. I am going to post a new link right now for easiest way to lube up my cables without a teardown. Bet ya have way better luck after those wires get changed. ALso...keep the little black boots from the switchbox and coil ends of the wires and REMEMBER to put them on before crimoing new ends on the wires. Learned the hard way LOL. Good Luck. Keep me posted as there aren't many motors closely related to ours that i have seen on this forum.

 

[Jeff Lindquist]

Re: 1979 Mercury 80 hp puking out...

oh, pics never came through. please send to jeffl@tsmetals.com so i can take a look and compare.

 

[arkhogball]

Re: 1979 Mercury 80 hp puking out...

I'm sorry for jumping in on this tread, but I'm having some major wiring issues as well with this motor. One of my wires that is completely broken is attach to the blue cylinder shaped thing in the picture. What is that piece called? I've got to get a new one. Any help would be greatly appreciated.

 

[Jeff Lindquist]

Re: 1979 Mercury 80 hp puking out...

sorry just got back from a week of fishing with no major issues. i dont see your pic, but sounds like the mercury switch that prevents thte motor from running if the leg kicks up by contacting an underwater structure or something. i removed mine totally as any major impact on the leg will be bad enough that a writeoff may be preferrable. send a pic on your next reply please