1979 Mercury 80 hp starting problem

[natecollins1]

Hi,

I am working on a 1979 Mercury 80 hp outboard. I am only able to get it started if I fully advance the timing arm on the motor or using the warm up lever (which does the same thing on this motor). At first I thought the problem might be that it did not have the proper fuel mixture when starting. I tried to start it using the choke with no success. Next, I tried to spray some starter fluid w/ lube at start up, again with no success. Last, I tried to start with the carb butterfly valves wide open - again w/ no success. It only starts if I fully advance the timing arm. Once I get the motor started it idles a little fast (probably 1000-1200 rpm). Also, the lowest I can get the idle timing down to without cutting out is about 6 btdc. The spec calls for between 2 btdc and 2 atdc. I have adjusted the idle mixtures screws to what I believe is the sweet spot. I am about a 1/4 turn richer than the spot where I notice a change in rpm. I did a spark test with a spark tester and all cylinders are getting a good spark when cranking.

Please help. Thanks.
Nate

 

[hkeiner]

Re: 1979 Mercury 80 hp starting problem

Have you done a FULL link and sync, from beginning to end? Each link and sync step/setting is dependent on all previous steps/settings being correctly done. If one step/adjustment is incorrect, it negatively affects any subseqent steps/settings you try to do/adjust.

 

[natecollins1]

Re: 1979 Mercury 80 hp starting problem

Hi,

I have done a complete sync-and-link. The best I could get was about 6 dbtc when adjusting the timing without having the engine cut out. I performed everything just as the mercury service manual specified.

Thanks,
Nate

 

[j_martin]

Re: 1979 Mercury 80 hp starting problem

If you skipped the test where you measure the piston dept before TDC and compare it to a flywheel mark, that is where your problem is.

Assuming you have good compression, sounds like yer timing mark is off.

hope it helps
John

 

[natecollins1]

Re: 1979 Mercury 80 hp starting problem

Hi,

I checked the timing mark using a dial indicator as the service manual states. It is dead on.

I took the boat for a ride today on the water. It was having a little bit of trouble cutting out when I shifted it into gear. It was also appeared to be starving for fuel when I accelerated. I was able to push the choke when accelerating and it gave it a little more power. I will clean the carbs to resolve this issue. I probably have some trash in the high speed jet.

I am still stumped about the fact that I have to advance the timing all of the way to get it started.

Any help is appreciated.

Thanks,
Nate

 

[Chris1956]

Re: 1979 Mercury 80 hp starting problem

Nate, Before you clean the carbs, richen the idle mixture 1/8 turn, top carb first. Then try to accelerate. If you need to richen the bottom carb, do that next. You should get a lousy idle but good acceleration, that is normal.

As for your timing issue, on my '77 distributor Merc 1500, the idle timing was 4-6 BTDC. So, you may be Ok on that one. Make sure you do not adjust the primary pickup, once you have set it to 4-6 BTDC. Just back down the idle stop and cable barrel to slow the idle RPM.

 

[natecollins1]

Re: 1979 Mercury 80 hp starting problem

Hi,

Thanks for the info. While I was out on the lake today I did try opening up the idle mixture screws about a 1/4 turn. This did help some, but I could still feel some trouble accelerating.

I also did as you said about the sync-and-link. Where I have everything set now, if I adjust anything to slow the motor down it will die out.

I will probably try cleaning out the carbs next and that way I will have one less thing to worry about while making my adjustments.

Thanks,
Nate

 

[hkeiner]

Re: 1979 Mercury 80 hp starting problem

It was also appeared to be starving for fuel when I accelerated.

Fuel starvation can be a serious situation. If you run the motor too lean at high speed, you can burn up the pistons and such. To relieve any concern over possible fuel starvation caused by a weak fuel pump or the fuel system upstream of the fuel pump, there are tests you can do with a vaccuum gauge and some clear hose. Mercury issued a Service Advisory that describes how to do this.

If it is "starving" only during accelleration, then the excellent advice you already received, regarding adjustment of the carb jets, should do the trick.


http://www.marinepartsman.com/Mercury-Marine-service-bulletins/Mercury-Mariner/2001/EN_17.PDF