Diagnose *pics* of spark plugs>

[westexasrepublic]

Cylinder 3

Cylinder 2

Cylinder 1

79' mariner 70 HP

Cold engine bogs and only reaches 2500 WOT. Warm engine "burps" makes a burping, and boom, 5500 WOT. What can you tell me?

BRAND NEW> Spark Pulgs/Stator/Trigger/Rectifier/wiring harness/fuel lines & fittings.

 

[jake505]

Re: Diagnose *pics* of spark plugs>

plugs look pretty good except for number 1 little bit of build up could be a leaky carb, not familiar with that exact engine but maybe you have a bad reed valve that might cause it. how about you fuel mix ratio maybe its to rich should be 50:1 i believe.

 

[westexasrepublic]

Re: Diagnose *pics* of spark plugs>

yah cyl 1 is exactly what I was wanting to point out. I have a 50:1 ratio, but I have dual carbs, that I didnt rebuild but took apart and are very clean. Im not sure what a reed valve is? ill look into it. Also could it be a bad coil? seems like its not getting a good spark if one at all cuz the fuel seems not to burn well in that cylinder, hence the fouled plug, right?

 

[lowkee]

Re: Diagnose *pics* of spark plugs>

How does the compression check out? Low compression in that cyl will cause a fouled plug.

 

[westexasrepublic]

Re: Diagnose *pics* of spark plugs>

dont have a compression tester, Im getting one soon, but wondering if the local Oreilly's borrows them out?

 

[jake505]

Re: Diagnose *pics* of spark plugs>

well I would say your definatly getting spark or it wouldn't be fouled out. what causes fouling is the fuel in the cylinder not burning completly usually because its running to rich, meaning to much fuel and not enough air if you had no spark the plug would be clean because the fuel would wash the plug every time it stroked. I suppose weak spark might cause it but i dont think it is a spark problem.

I would check the compression and then go from there oriellys might rent it but I'm not sure b/c I dont have any around me all I have is advance and autozone if they dont rent it you can all ways buy one you can get one for about 30 bucks, not sure if you have any harbor freight stores around you but I know they have one for 10 bucks that would do the trick

Just curious did this symptom start after you cleaned the carbs or is this the reason you cleaned? just wondering because if it happened after could be that you didn't adjust the carbs right after you cleaned them which is an easy fix just adjust the flow rate a little, but I would imagine you cleaned them because of this problem.

 

[westexasrepublic]

Re: Diagnose *pics* of spark plugs>

I took the carb apart and inspected, it was clean, real clean. so I really didnt do anything to it beside put it back together with a little gasket sealer around it. But the symptons I have on the plugs are recently since I messed with the ideler screws. So im gonna try and lean it out a half turn maybe?

 

[j_martin]

Re: Diagnose *pics* of spark plugs>

I took the carb apart and inspected, it was clean, real clean. so I really didnt do anything to it beside put it back together with a little gasket sealer around it. But the symptons I have on the plugs are recently since I messed with the ideler screws. So im gonna try and lean it out a half turn maybe?

Just for grins and giggles, why don't you get a manufacturer's maintainance manual and set up the linkage, timing, and mixture to the proper specifications?

 

[westexasrepublic]

Re: Diagnose *pics* of spark plugs>

well I have the manual. So I got the numbers, and I keep tinkering but cant get results. I just got a guage, and checked all 3 cylinders, and heres the numbers.

cyl 1 - 105 psi coil test good
cyl 2 - 120 psi coil test good
cyl 3 - 115 psi coil test good

I guess I now need a timing light, of course, more tinkering. Any other thoughts?

 

[lowkee]

Re: Diagnose *pics* of spark plugs>

Not sure if anyone else mentioned this.. but did you set check the points? They may be too far apart and misfiring at high RPM, since the coil isn't able to build enough of a charge to jump the (larger) gap. May explain the 'boom', as it would have unburned fuel every few rotations in addition to the new fuel. You will still see spark in this case, but it will mess up at high RPM (your original issue). I'd just get a points and condensor set and throw a new one in anyhow ($15 normally). You would be amazed what a bad point gap can do, or even a dirty set of points (I've gotten away with fine sandpapaer to clean them until new ones arrived).

 

[westexasrepublic]

Re: Diagnose *pics* of spark plugs>

where do I find a condensor/points for a 79' mariner 70 HP (3cyl)? ser#536xxxx

also the only thing I havnt replaced electrically is my switchbox, is there a way to test one?

 

[lowkee]

Re: Diagnose *pics* of spark plugs>

That part I'll have to pass off to someone who knows this particular engine. I'd guess under the flywheel, unless it has a cap and rotor. Don't worry if you've never popped a flywheel, they are easier to remove than many think.

 

[Faztbullet]

Re: Diagnose *pics* of spark plugs>

This engine has no points,its a ADI ignition setup. I would suggest you look towards weak/no spark due to bad plug wire,bad coil,failing trigger or defective switchbox. I will lean more toward switchbox/trigger as these will make spark come and go giving you the "burping" and then cylinder kicks in and boom your away. Check the wiring on trigger as these are known for the insulation falling off.

 

[westexasrepublic]

Re: Diagnose *pics* of spark plugs>

I knew the points thing didnt make sense...I just thought I didnt know my outboard. Coils test good, and Trigger is new.

How do I check for defective switch box and plug wires?

 

[westexasrepublic]

Re: Diagnose *pics* of spark plugs>

OK so if i am understanding right, a symptom of the "burp and go" is a failing switchbox, is this correct?

for instance yesterday it fired up good, idled good. Left the no wake zone and full throttle 3000rpm, bog bog bog, more bogging and the blurp burp burp and the rpms jump and all of a sudden im up on plane and running 5400. for the most part the rest of the day runs fairly normal, sometimes gets the "burping"