305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

LX Kid

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Yup I'm still alive and kickin. Still have this old problem, that I haven't worked on in 4 months. In the yard the boat motor runs great with no problems. When I launch and get about 100 yards from the dock it just dies. Seems the coil is not getting any spark. Might, maybe, could be that between the starter to key switch might be a problem. Anyone ever had this happen on their 305 I/O Mercrusier?
 

Don S

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

Coils don't "Get" spark, they make spark.

When it dies, take the coil wire out of the center of the distributor. Hold the end of the wire about a half inch from a good clean ground and crank the engine over. You should see a bright blue/white spark snap across the gap.
If none, then check to see if you have voltage to the coil on the + terminal of the coil with the key in the run position.

What ignition system do you have? Points? Thunderbolt IV, other?
 

LX Kid

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

Coils don't "Get" spark, they make spark.

When it dies, take the coil wire out of the center of the distributor. Hold the end of the wire about a half inch from a good clean ground and crank the engine over. You should see a bright blue/white spark snap across the gap.
If none, then check to see if you have voltage to the coil on the + terminal of the coil with the key in the run position.

What ignition system do you have? Points? Thunderbolt IV, other?

Points! Won't fail while in the yard no matter how long I run the engine. To me that almost rules out a bad coil. If I remember correctly, ha, I "think" I checked the + wire and it had no voltage when I got stranded twice. I believe that it's related to the outdrive being in gear somehow. When I get a chance I will put it in gear, while in the yard, and see what happens. (Don't suppose it will hurt anything.)

I also felt with my hand down on the starter to see if the coil wire was loose but seems like everything was tight down there.
 

Don S

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

I also felt with my hand down on the starter to see if the coil wire was loose but seems like everything was tight down there.
That wire won't have anything to do with it, it ONLY puts power to the coil during cranking of the starter, no other time.


If I remember correctly, ha, I "think" I checked the + wire and it had no voltage when I got stranded twice.
That is what you need to confirm. Even if you have to go to the water.


I believe that it's related to the outdrive being in gear somehow.
If it was the shift interrupt system, it would probably stop when you put it in gear. But if this also happen in gear when you throttle up, then the shift cables could be really far out of adjustment.
Have you tried running it on muffs and in gear?
If it dies on throttle up, you might be able to watch the shift interrupt switch Y bracket that activates the switch and see if it's moving when you throttle up.
 

matt167

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

Does it load up with gas, or just quit?. Not a boat, but I had put a cheap green set of Std ignition points ( instead of blue streaks ) in the old '65 Rambler I had. Car would run and idle great, rev up and run like a swiss watch. Put it in gear and try to move it and it fell on it's face, load up and die. I changed everything I knew to except the points because they were new. Once I stuck that $10 set of blue streaks in, it had the power it should. I never hooked a light to it, but I expect point bounce was so bad it was actually firing erratically.

This does sound more like the interrupt switch. you could bypass the switch with a manual toggle to do the same thing as a test.. If it keeps running, you need a new shift interrupt switch
 

Fishermark

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

However you test it - whether on land with muffs or on the water - once it dies, be sure to leave the control handle engaged in gear. Then look at the shift interrupt switch to see if it is physically engaged or not. It shouldn't be. If it is, then you have found your problem. If you take it out of gear and back into neutral after it dies, you will "unbind" the cable and you may then have power again to your coil making diagnosis difficult.
 

Don S

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

.. If it keeps running, you need a new shift interrupt switch

Why would he need a new switch? The switch is designed to kill the engine, what he would need is to fix what is causing the switch to be activated.
 

matt167

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

Why would he need a new switch? The switch is designed to kill the engine, what he would need is to fix what is causing the switch to be activated.

well, right. The switch is either no longer working correctly or it is out of adjustment.. If the switch was contacting internally while in the open position, it could do the same thing. But adjustment would be the first thing to check
 

NHGuy

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

So does it go 100 yards with the throttle at least partway open, or is it at idle? Is it just getting warm when it dies? Or is it fully warmed up? Could you just troll around at idle indefinitely or does it have to do with being in the water?
 

LX Kid

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Re: 305 Mercrusier I/O Stops 100 yards from dock!!!!!!!

So does it go 100 yards with the throttle at least partway open, or is it at idle? Is it just getting warm when it dies? Or is it fully warmed up? Could you just troll around at idle indefinitely or does it have to do with being in the water?

It idles on out the boat launch for about 100 yards and dies. The engine is at operating temp and only happens while in the water. Maybe it has something to do with being in gear and under way. I haven't had the boat in the water now for about two years, because of this problem, and only recently got interested in repairing it. (I hope!)
 

achris

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The first thing you need to do is to determine if it's spark or fuel. Before you head out, connect up a timing light, and if you can find one of the old 'in line' lights, all the better. Have the light laying on the floor and do what you normally do. Ideally have someone with you to watch the light. When it dies, just pull it out of gear and crank. See spark, it's a fuel problem. Then check the carb. Take the cover off and have someone look down the barrels as you give it full open (engine not running of course. See if they see any fuel being squirted in...

Best I can suggest at this point..

Chris.....
 

LX Kid

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Gonna have to give it another try while in the yard instead of launching. I haven't renewed the registration nor the trailer registration and don't want the hassles. Won't start with switch and have to jump starter relay. Think I'll check ignition wiring and replace the ignition switch before going any further.
 

achris

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Have you tried running it on muffs (on the trailer) in gear... Simulating the 10 yards travel as closely as possible...?
 

alldodge

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Gonna have to give it another try while in the yard instead of launching. I haven't renewed the registration nor the trailer registration and don't want the hassles. Won't start with switch and have to jump starter relay. Think I'll check ignition wiring and replace the ignition switch before going any further.

I'm thinking it could either be a bad key switch or loose connection up there. Boat runs fine on muffs and doesn't die, only dies in the water running. When running in the water there is more movement. Get it running and wiggle the key and wires behind it
 

Fishermark

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...I haven't had the boat in the water now for about two years, because of this problem, and only recently got interested in repairing it. (I hope!)

Not to add to your problems... but you probably have compounded problems now. If you still have the old fuel in it you are going to have additional issues to deal with, which will hurt the diagnosis of your original problem. Just something to be aware of. You might want to run it on a portable outboard tank for diagnosis purposes. That will take one of the potential problem areas out of the equation.
 

LX Kid

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Not to add to your problems... but you probably have compounded problems now. If you still have the old fuel in it you are going to have additional issues to deal with, which will hurt the diagnosis of your original problem. Just something to be aware of. You might want to run it on a portable outboard tank for diagnosis purposes. That will take one of the potential problem areas out of the equation.

Gas was treated and there is no laquer type smell and does smell normal. I have already been running it on this gas and it seems fine.
 
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