Mariner Magnum III won't even crank

[msujcrew1]

i inherited a boat with a (i think) 94 Magnum III outboard. when i first got it and cleaned out the gas tank, it ran very well with no problems. the alarm at the console would stay on constantly, but the oiler was working and the temperature sensors appeared to be working correctly. after a few times of taking it out, it started to miss enough so that it wouldn't plane out. i changed the spark plugs and cleaned the carbuerators, but it still wouldn't run properly. actually it started running only at a good idle. if i gave it some throttle, it would just choke out. the next time i took it out it wouldn't run well, but at full throttle would only be a good idle. coming back to the landing, the motor went dead and will not crank again. I've taken the carbs off again and cleaned them, used a different gas can to make sure the gas wasn't bad, but it still will not crank. it will turn over, but won't try to crank. i haven't checked the spark plugs again. about half way through this process, the tachometer started acting up. it would work some of the time and not work at others.

any idea what may have caused this?

is there a way to adjust or check the timing on this motor?
any help on this would be appreciated.

 

[achris]

Re: Mariner Magnum III won't even crank

Would love to know more about the engine, like the serial number....

How do you know the oil injection was working? What type of alarm, solid or beeping?

What it sounds like to me is that the oil injection system was not working and you seized the engine through lack of oil...

Can you turn it over by hand? If so, then is the starter engaging and not turning?

I may getting mixed info about 'crank'... Cranking is the electric starter turning the engine.... If it's not cranking, then that means the engine is not turning over... If you mean that it is cranking, but not firing, then you have other issues... The tacho acting up will be the battery going flat.... Because your cranking it a lot.....

Do a compression test, check you have spark on all cylinders and in the right firing order... It's complicated on these engines... 1-2-3-4-5-6.

Need more input.....

Chris............

 

[msujcrew1]

Re: Mariner Magnum III won't even crank

the serial number is OD239952.

the starter is turning the motor over. i checked the spark plugs yesterday evening and could not get a spark in any of the plugs and they aren't but a couple of weeks old.

the tachometer was cutting in and out while the motor was running. (back when it was running) Will a flat battery or loose connection at the battery cause the tach to cut in and out while the motor is running?

if you could please give me a quick overview of how the firing system works?

 

[Boatleech]

Re: Mariner Magnum III won't even crank

One serial number list I looked in said yours was a 1994, but the manual I've got doesn't cover the Magnum. For discussion purposes, I'll assume it's similar to my '94 40HP.

Things start out in the stator, which is a series of coils wound on bobbins along the circumference of a circular assembly mounted on the powerhead. The flywheel has several magnets on it, which fly by those coils when the flywheel is turning. This generates current in those coils, which is used to charge the battery, pulse the tach, and spark the plugs. The battery and tach current go through a rectifier, and the sparkplug current goes through a switchbox, where another pulsed current from a trigger directs a timed spark pulse to the appropriate cylinder.

You really need some basic test instruments to track down the problem. It's simple troubleshooting, but impossible to do without the equipment, unless you just throw parts at the problem, but in some cases you might put on a new part A, only to have it fried by defective part B which you haven't changed yet.

With a digital VOM and a DVA adapter, you can easily narrow down the source of the problem. A remote starter switch helps, and if it looks like you're going to be replacing the stator, trigger, or flywheel, you'll need a flywheel puller. Other than those, simple hand tools are about all you need. Oh -- and a manual.

 

[msujcrew1]

Re: Mariner Magnum III won't even crank

it's a 6 cyl 150 hp.

so the trigger is under the flywheel as well as the stator??? do i test for power coming from the stator? if there is power, then i test coming from the switchbox, and so on.....?

 

[Boatleech]

Re: Mariner Magnum III won't even crank

Pretty much. On mine, you first check resistance values for all the coils involved, check for shorts to ground, and check to make sure the kill circuit isn't killing things when it shouldn't be. Then you can remove the plugs to lighten the cranking load, and check for voltage output from the stator & trigger, and trace the high-voltage circuit through its path to the plugs.

Another check in the instructions for installing the new switchbox was to make sure there was no DC voltage on any of the kill wires -- that apparently spells death for a switchbox, according to the switchbox manufacturer.

You really need a manual... best $40 or so you'll spend.

 

[msujcrew1]

Re: Mariner Magnum III won't even crank

thank you for your help.

this is what i know so far. there are three sets of wires coming from underneath the flywheel.

1) one set has six wires which in turn split into two sets that run to the front and back of the switch box. these wires are brown, light blue, and gray. i checked the voltage of these wires when the starter is turning over. the voltage floats around 5 or 6 volts. there is very little voltage (less than 1 volt) in the green wires that run from the switchbox to the rear of the motor where they are hooked up to the coils where the spark plug wires are plugged in.

1a)do these wires coming from the flywheel to the front and back of the switchbox come from the trigger or stator? (i'm guessing the trigger and i'm trying to read a pulsed current, and i'm getting low voltage on my meter)

2) the next set of wires coming from the flywheel are yellow and run to the rear of the engine into two sealed boxes. i'm thinking that this is the rectifier that you mentioned. there are 12 volts in these yellow wires and 12 volts in the red wires (even when the starter is not turing) that are coming out of these boxes. i also noticed that there are yellow wires that i can see around the coils of the stator.

3) the third set of wires coming from the flywheel go to the top "row" of the switchbox. when the starter is turning, the voltage in these wires are about 5 to 6 volts.

4) when the motor was running, the tachometer would quit working for a few seconds, then start back, then stop again. the trigger gets it's current based on the position and speed of the crankshaft, correct? does the tachometer use this same pulse as the switchbox to work??

5) how much voltage should i be getting in the wires going to the top "row" of the switchbox? i'm guessing that this is the constant supply to the switchbox from the stator. how much voltage comes into the switchbox at the two sets of three wires, and how much voltage should come out of the switchbox going to the spark plugs?

 

[Boatleech]

Re: Mariner Magnum III won't even crank

I'm sure you're right about the yellow wires. They provide AC which is rectified and used in the charging circuit. The tachometer is driven off of one of these wires. I think the 3rd set are the trigger, and the first set are the ignition. Unfortunately, I have no service literature for that motor, so really can't help you much more.

 

[achris]

Re: Mariner Magnum III won't even crank

Yellow wires are the battery charging system and are completely isolated from the ignition system. The tacho is attached to the charging system and is also isolated from the ignition.

The ignition system is also split into 2 separate systems, odd cylinders and even cylinders. The only things in common with both is the kill wire, going to the control box ignition switch and the bias wire, a white wire that ensures that both switchboxes are firing with the same amount of advance. The trigger wires are sort of shared also.

This diagram should help you. The stator wires to the switchboxes are red (high speed) and blue (low speed) to one switchbox and red/white (high speed) and blue/white (low speed) to the other switchbox. Trigger wires pairs are brown, white and violet. One set with have a yellow sleeve over then to identify them as going to the same switchbox.

Chris...........

 

[msujcrew1]

Re: Mariner Magnum III won't even crank

what should the voltages be at the red , blue and red/white, blue/white wires? i'm getting about 5 volts at the low speed wires going into the switchbox when the starter is turning.

 

[achris]

Re: Mariner Magnum III won't even crank

You need to use a DVA to measure voltages at the Stator... I think iBaots sells them and they aren't expensive...

 

[msujcrew1]

Re: Mariner Magnum III won't even crank

what color is the kill switch wire, and where does it attach to the engine at? i thought that i had found it, but it turns out that i had not.

also i've read about a mercury switch? would this motor have one? if so where is it at?

i've measured the resistance of the trigger wires based off of the information i found. the sheet specified that the resistance between the certain trigger wires should be between 800 and 1400 ohms. i'm getting about 1260 ohms. does this mean that the trigger is okay??

the sheet also says to measure the resistance from the blue and red wires going from the stator to the switchbox from the wire to a ground. it says 5000-7000 for the blue wires and 90-200 for the red wires. i measured 115 for the blue wires and only 1600 for the redwires. did i measure wrong or does this indicate a problem?