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30 HP Mariner - has spark, compression and fuel - no start

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briansthomas

New member
i have a 30 hp mariner that i believe is from 1979 - model 30M 689 S 014793

The engine has 120 psi cold compression and it has spark when plugs are grounded to block. The engine will not fire at all even with starting fluid in cylinder or carb. The engine looks like it is very low hours with zero corrosion anyplace. I cant seem to get it started for the life of me - wont even fire.

It has the type of coils where both plugs fire from 1 coil - i have not changed the plugs but i cleaned them and they look in very good shape.

Has anyone seen where the key under the flywheel sheers or moves and the timing might be off?

thx in advance for your help!!
 
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Yes check the flywheel key.------Plugs on the block is not a proper test.----Does spark jump a gap of 3/8" or better ?-----Did you try swapping plug leads ?
 
racerone said:
Yes check the flywheel key.------Plugs on the block is not a proper test.----Does spark jump a gap of 3/8" or better ?-----Did you try swapping plug leads ?
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hmmmm - i doubt it will jump 3/8 of an inch? - i have an adjustable spark tester but i set it at about 1/8th of an inch figuring that has to be 2X the plug gap? i have never heard that it would need to jump anywhere close to that?

i have tried swapping leads but i have a feeling this is a coil that fires both plus at the same time no matter what - back in the 70 and 80s these were common

what concerns me the most is that it wont fire starting fluid - i would think the smallest spark would ignite starting fluid?
 
racerone said:
Find out why you have weak / no spark.-----Repair the ignition system !
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i dont know - it has a spark and it is not terrible - it jumps at least an 1/8 of an inch and i would think that would ignite the starting fluid? i am going to try increasing the gap on the tester later -
 
racerone said:
Find out why you have weak / no spark.-----Repair the ignition system !
Click to expand...

i meant to ask raceone - any idea what the gap should be on this plug? i have seen both .024 and .035 - it looks like it is .024 or less now - i have not tried new plugs because these didnt look fouled and instead i cleaned them
 
A plug gap of 0.030" works.------But perhaps you are not aware that spark can jump that gap in air at 14.7 PSI.----But your ignition system needs more voltage to jump that gap in the cylinder with air at 120 PSI.-----So based on the information you have posted , I say you no not have spark with plug in the cylinder !!
 
racerone said:
A plug gap of 0.030" works.------But perhaps you are not aware that spark can jump that gap in air at 14.7 PSI.----But your ignition system needs more voltage to jump that gap in the cylinder with air at 120 PSI.-----So based on the information you have posted , I say you no not have spark with plug in the cylinder !!
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i am actually thinking u might be correct - i say that because in daylight (not direct sun) i struggle to see the spark and I do not recall ever having that issue - at first i thought it had no spark until i tried the test when it was dusk and then i could see it.

I am without the manual rt now - what might you suggest? i know enough to be dangerous but have lots of experience on auto and race engines and i have a degree in internal combustion engines - if i am not mistaken the stator is where the voltage comes from? I am not certain how to test it? also someone gave me the boat and engine and i dont want to throw parts at an old engine where it might be difficult to maintain it cause of lack of parts?

I am going to throw new plugs in it this AM even though i dont think it will help! but for $10 it likely makes sense. thx for your assistance!! I live in dania beach if u know any mechanics that might be able to better diagnose it than me
 
Okay, I'm in. You have inadequate spark, my friend. The spark should be a very strong lightning like jolt and be able to jump 3/8 to 7/16" out in the air. The color should be a blue/white. Almost every Merc that I have had of this vintage, has come to me with weak or no spark. You can check the spark with a #2 Phillips screwdriver pushed into the spark plug boot and held the required distance from a ground, while a helper pulls over the motor. The problem will then be found, and we can diagnose your electronic ignition. With Mercs, it's most often the switch box, which can't really be tested, but it has to be done by first testing the other components with your multimeter with DVA capability. Then using the process of elimination. If you are on a tight budget, I can help you find tested, used components.
 
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i am starting to agree with you - the spark is there but too weak to even ignite the starting fluid once under pressure - i have an adjustable spark type gauge and i just ran outside and set it to 1/4 inch gap - and the spark wont jump it - it will jump .025 but without the typical snap with a bright spark.

So where do i go from here? i am not sure what a DVA is although i have a quality multi meter?

by the way this engine was made by yamaha about 1980 and labeled as a mariner 30M S 689 xxxxxx



timguy said:
Okay, I'm in. You have inadequate spark, my friend. The spark should be a very strong lightning like jolt and be able to jump 3/8 to 7/16" out in the air. The color should be a blue/white. Almost every Merc that I have had of this vintage, has come to me with weak or no spark. You can check the spark with a #2 Phillips screwdriver pushed into the spark plug boot and held the required distance from a ground, while a helper pulls over the motor. The problem will then be found, and we can diagnose your electronic ignition. With Mercs, it's most often the switch box, which can't really be tested, but it has to be done by first testing the other components with your multimeter with DVA capability. Then using the process of elimination. If you are on a tight budget, I can help you find tested, used components.
Click to expand...
 
Okay, good. I have the exact motor in my shop. It is a very good motor, the last of the Yamaha Mariners. Is yours electric start then?
 
timguy said:
Okay, good. I have the exact motor in my shop. It is a very good motor, the last of the Yamaha Mariners. Is yours electric start then?
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it is very interesting you say that - i keep reading articles about how people really liked these motor? evidently they held up well. do you have any idea on how i can troubleshoot this likely weak spark issue? i think mine is like a 1980 and is not electric start and i think i might have found the correct manual but have not gotten it yet - i am hoping it will include troubleshooting with specs for the ignition system?
 
Yes it should. I don't have specs for pre 1984 Yamahas. Normal DVA, (or peak reading), is 170 volts minimum with spark plugs out and a spin of at least 250 rpm. That is taken at the wires coming from the stator while still hooked up. Most Yamahas you will go between the blue wire and the black/red. Then the other black wires, with either green or white....should produce about 190v peak voltage when measured to ground. Any primarily white wire, with red, black, or green stripe should produce a minimum of 3 or 3 1/2 volts. A resistance test can be done between the brown and blue. Ohms should read somewhere in the 115 to155 range. Triggers which I think use a black and a white/red, should indicate around 12 to 18 ohm's. Be sure to operate the throttle from idle to wot when testing trigger. Why? There may be a break in the wires' conductor that you can't see, causing a problem in certain operating positions. This is what I have for 1984, which may not help you alot, however. The final coils should read a primary resistance of .5 ohms and a secondary of 3 to 4 thousand ohms. DVA adapters are available for most multimeters and are a "must have" for effectively diagnosing marine electronic ignitions.
 
thanks so much for the info - i have ordered the manual and maybe between it and your help we can figure this out! i am not exactly certain how to perform the tests but i hoping the manual will help!!!~ happy holidays !




timguy said:
Yes it should. I don't have specs for pre 1984 Yamahas. Normal DVA, (or peak reading), is 170 volts minimum with spark plugs out and a spin of at least 250 rpm. That is taken at the wires coming from the stator while still hooked up. Most Yamahas you will go between the blue wire and the black/red. Then the other black wires, with either green or white....should produce about 190v peak voltage when measured to ground. Any primarily white wire, with red, black, or green stripe should produce a minimum of 3 or 3 1/2 volts. A resistance test can be done between the brown and blue. Ohms should read somewhere in the 115 to155 range. Triggers which I think use a black and a white/red, should indicate around 12 to 18 ohm's. Be sure to operate the throttle from idle to wot when testing trigger. Why? There may be a break in the wires' conductor that you can't see, causing a problem in certain operating positions. This is what I have for 1984, which may not help you alot, however. The final coils should read a primary resistance of .5 ohms and a secondary of 3 to 4 thousand ohms. DVA adapters are available for most multimeters and are a "must have" for effectively diagnosing marine electronic ignitions.
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Okay we will be standing by here. I check the Forum usually 2 or 3 times a day. And yes, ~ same back to you!
 
HAPPY NEW YEAR TO ALL!

hopefully i get this running before next year!!

So i got the manual and a multi meter and i tested the stator coils and they both test OK, then i tested the primary coil and it tests ok, However the secondary coil test does not meet specs - it does not show any continuity or resistance at

this motor has a buddy type coil where one coil fires both plugs at the same time, the manual says to check resistance from one plug lead to the other - i get zero or no connectivity, i tried checking from the secondary to both the coil ground and coil hot and i do not any continuity - meantime i was able to buy the entire ignition system for $30 shipped and i grabbed it. however that coil (the extra one i bought) reads the same of my coil that came with the engine

i tried swapping the new used coil for the original one but still have pretty much hardly any spark at all,


any and all ideas are helpful thx in advance!




timguy said:
Okay we will be standing by here. I check the Forum usually 2 or 3 times a day. And yes, ~ same back to you!
Click to expand...
 
By next year? Man you didn't give yourself much time. Does your diagnosis include a DVA test on your stator? In other words, some peak voltage specs? You will test stator output with a nice brisk pull and probably with plugs out, in order to see how close you can get....no use pulling your shoulder out of whack.
 
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