1979 75hp stinger rough starts/idle

[TraskRiver]

Another new guy. New to Boating as well. Bear with me as I'm sure these might be questions youve heard a 100 times.
Appreciate any help in advance.

Just recently acquired a 1979 75hp stinger. Was told it was recently gone through. I'm sure we've all been told that.

It has a serious hard time starting. More so in the water than on the muffs. Cold or warm starts seem to be the same.
I can have some video up tomorrow evening as I know that will help.
Here are my cold start procedures:
1. Prime fuel bulb
2. fast idle start position (more details below)
3. push key in and turn over

Ive tried it other ways as well with the same results.
The fast idle lever does not seem to be adjusted correctly. At full lift it only moves the linkage a fraction and does nothing to the idle while the engine is running so I am assuming it is not doing it's job. The fast idle lever on my dad's boat will put that thing into a screaming idle.

Motor Fires right away and then dies instantly with a little spit/sputter. After that I continue to hold the choke and crank for about 15 seconds as it slooowly starts to fire and gradually come alive. When it finally starts there is the smell of raw gas and a decent plume of blueish smoke. It seems it is loading up.

Anything other than an idle and it seems (to me) to run great. Have had it out on the lake for hours and it loves a medium to full throttle. Doesnt seem to skip a beat at those rpms.

It does not like to idle down smoothly and has the same rought start and sometimes no start at all even after warmed up. I was almost stranded on the lake yesterday! It would have been a long paddle back.

I'm getting a lot of small backfires when it does not want to start and oil/fuel spitting from the carb

I pulled all 3 carbs last night and went through them to get familiarized (new to me). They seemed as clean as they possibly can be and as if someone has recently been in there.
I've been around a few carbs but am used to having low idle/ fast idle/ main and pilot jet/ air fuel etc adjustments. Are there no adjustments for these?

I will be doing a compression check tomorrow and also check the spark gap.
Anything else to keep my eyes on while in there?

I'm a fast learner and have been around tools/mechanics for a long time. Just not 2 stroke outboards.

Thanks guys

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Hi
Thats a well written written post- good start.

Try cranking it and put your palm over the carb throats to check you get even suctions from both carbs.
So it idles ok?
Its always impresses me with some motors tuned right how little timing base movement by the fast idle lever is needed to get a very accerrelated idle

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Thanks

I forgot to mention that as far as I know I am using the correct fuel and the fuel is fresh. 92 octane ethanol free with twc3 50:1 oil ratio.

This is a 3 cylinder. I will check the suction while turning over tomorrow to see if all 3 carbs are pulling the same. I would imagine if not then it should show up in compression results
It does not idle very well. Hard start and very shaky and sputtery at idle (when I can get it to start) But once it smooths out a bit I can throttle up and drive the boat with no issues. After a decent run in the higher rpms it does not like to idle down. It takes a while to settle back into an ide and then becomes shaky and seems to misfire. If it dies right after a good run then it is even harder to start. Seems to be loading up.

I'll report back with the basics/standards as far as compression and spark testing. Go from there.
Thanks again

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Yep thats the way with compression test.
Compression can sometimes be fine but the vacuum on the carb throats will be uneven, becauses if the inlet reeds are damaged it will blow back from the inlet manifold

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

They look like they are all fixed orifices on that model

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Gotcha. Reeds... I keep forgetting it is a 2 stroke. I am getting oil/fuel spit from the carbs so I will check that.
Here's a newbie question... is there a way to visually inspect the reeds?

Thanks

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Not really until you take the manifold off and have a good look but the suction test normally gives it away somethings wrong.
You could try a small inspection mirror and look for any broken fins

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

It can be your upper and or lower seal sometimes too if you isolate it to one of those top or bottom carbs

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Update:

Compression was 145 across the board. Spark test indicated a completely dead coil. The other 2 coils had great spark that was jumping 1/2" consistently.

Tested the carbs for suction and they all seem to have decent suction. Hard to tell but it seemed the middle carb had maybe slightly less suction but not that noticeable.

So no spark on the top coil. Also, a plug broke off as I was removing it, luckily just the top of the plug and was still able to remove it no problems. That I am sure is an indication the plugs are old and need changed.

Here's the question.... is it possible the no spark on one coil is a problem with the cdi or how would I go about testing that with a voltage meter or by resistance. I want to make sure it is a dead coil before I buy one.

How do I adjust the fast idle lever so it works? With someone cranking it and me holding the throttle open a little bit it starts a lot easier. So I need to figure out how to get that working again. Is there an adjustment in the throttle control? Or would it be adjusted at the linkage.

Another bad sign I found today is I found a small amount of what looks like gear oil/grease coming from where the prop is. It is not dripping, more so stuck around the outside edge of where the prop meets the lower unit.

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

You can swap the coils between cylinders/powerpack wires to check
Check your gear oil level and colour.
If your starter lever isnt moving it at all it may be a really worn cable

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Perfect. I should have thought of that. Going to try that right now.
The throttle cable works nicely. Just the fast start lever does not do anything. It lifts all the way up with no restriction and does not move the throttle open like it should. I'll have to take apart the housing and see if it is a problem on the inside.

Thanks bud

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Trying to remove the pin connector for the coil... am I supposed to just pull it out? or is there a special way to remove it

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

I dont know any special way so i just pull
Sometimes il pull and push with a micro screwdriver

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Gotcha. I got them swapped out. Just took some pulling.

Odd thing is once I swapped the bad coil with a good coil, they were all firing. Swapped them back to original position and they are all firing and jumping 1/2" gap with nice sparks. Maybe something was loose or there is an intermittent problem I am not seeing yet.

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Time for a test drive. You might find it starts failing as it heats up
If you have a timing light you can take it out and hook it up and just look at the flashes to check its sparking regularly

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Makes sense. I'm going to take it out today but before I do I'm going to change the plugs and inspect the prop seal. What is a good plug to run or should I just replace with the champions that were in it?
How many qts should the lower unit be for when I change it out?
Thanks

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Not sure about plugs sorry.
Lower unit should be around a litre or less, pump it up from the bottom plug (DONT UNDO THE PHILLIPS HEAD PLUG). If you fill from the top itl have a big airbubble in there and the upper bearing then wont get lube.
Boom bang

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

Got it. Oil level looks fine and oil on the inside looks fresh. I took it out today and did not see anymore residue at the prop...? It couldnt have fixed itself.

Fixed the fast idle lever. It was a loose mount on the inside of the lever not allowing it to engage. Now it works great and helps start the motor a lot easier. Still have a misfire though (new plugs). I ran the engine until hot and tested each coil for spark again and at this point I can't get it to fail like it did a few days ago. All 3 seem to be passing the spark test now but there is still a misfire. Is there a way to test the resistance of each coil? Or would that only pinpoint a primary failure. I know intermittent/weak coils producing low grade misfires can be tough to find.

 

[Bosunsmate]

Re: 1979 75hp stinger rough starts/idle

Just check its jumping at least a 7/16 gap
I think you will need to clean the carb channels

 

[TraskRiver]

Re: 1979 75hp stinger rough starts/idle

It is jumping gap just fine now. But a few days back the upper coil had no spark at all following a compression test. Mysteriously has spark now though.
I'll pull the carbs again. I fully disassembled and cleaned them a few days back even though they looked clean.
I don't have a timing light at the moment. I would be curious during low idle and some of the misfires whether it is a coil failing.