# Omc 5.7 problem



## vib-E (Jun 21, 2015)

The engine will start and fire.but won't stay running.pic of the coil...when the key is in the run position I have 5v on The right terminal looking down as in pic and nothing on the left terminal redwires..when I turn key to start the left terminal builds up to 8v then I stop cause the motor should be started...right terminal it climbs to 12v until key is released to run position...if I keep cranking engine the motor wants to run and keep fireing...so is the key switch faulty or something else I'm not aware of...thanks
















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## vib-E (Jun 21, 2015)

By the way..new points plugs.wires and coil.new fuel pump...filter.fresh gas...just to clear all that up...

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## backfar (Sep 24, 2014)

i would check the ballast resistor .the solenoid and the kill switch..


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## firemanmike2127 (Mar 17, 2013)

I don't think that there is a ballast resistor on the OMC's w/ a Cobra drive. The GM starter solenoid also has a second small terminal (marked with an 'I') that will provide extra voltage to the positive side of the coil when cranking. Have you checked the various wires on the positive side of the coil for a possible short to ground ? Mike


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## bajuski (Apr 9, 2004)

backfar said:


> i would check the ballast resistor .the solenoid and the kill switch..



I agree, the ballast resistor or resistor wire. With the key on you should have around 9 volts or more at the coil with a static engine. It is bypassed by the solenoid in the start position to get a hotter spark for starting only..Use a jumper wire between battery plus and jump to coil plus to confirm, the engine should continue to run. Don't leave the jumper on too long.


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## vib-E (Jun 21, 2015)

I'll check those things out.next available time....at least I got something to go by now...thanks guys

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## sherman51 (Apr 12, 2011)

first I would clean all contacts and making sure they are tight. its really hard to pin it down on a electrical problem.

if you still don't find anything wrong. try running a wire straight from the battery to the positive side of the coil. thats the way my older brother would take mom's car without a key. she started taking the coil wire with her to work. it didnt take long for him to see the coil wire missing. then he made his own coil wire. running a dedicated hot wire from the battery to the coil will tell you if there is a problem. if it starts and runs then you know its electrical.
sherman


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## firemanmike2127 (Mar 17, 2013)

Sherman's tip re: a direct 12 volt jumper/bypass lead is a good shortcut......especially if there is a weak spark condition. In this case (low supply voltage) I have 2 other thoughts. First is a coil winding that is breaking down. Second is the tach, which is connected to the Neg. side of the coil. Have you checked the voltage at the positive coil lead when it is disconnected from the coil ?


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## vib-E (Jun 21, 2015)

firemanmike2127 said:


> Sherman's tip re: a direct 12 volt jumper/bypass lead is a good shortcut......especially if there is a weak spark condition. In this case (low supply voltage) I have 2 other thoughts. First is a coil winding that is breaking down. Second is the tach, which is connected to the Neg. side of the coil. Have you checked the voltage at the positive coil lead when it is disconnected from the coil ?


No I did not..but I will do that....and I'll try Sherman's idea also...good thinking on his part....thanks again guys...I'll let u all know what I did and what the boat does as time allows

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## firemanmike2127 (Mar 17, 2013)

I'd check the resistance of the coil windings & also ensure that there is no short to ground within the coil itself. Before you connect the 12 volt jumper on the positive side of the coil do these 2 things. First, disconnect the other leads on the positive & negative sides the coil, except the breaker point lead to the distributor, of course. Secondly, measure the voltage present with just the jumper wire in place & also see what voltage you have present when the engine fires & is running. Another ?....did you make sure the points aren't shorted out to the breaker point plate inside the distributor (usually due to improperly installation) ? Mike


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## vib-E (Jun 21, 2015)

firemanmike2127 said:


> I'd check the resistance of the coil windings & also ensure that there is no short to ground within the coil itself. Before you connect the 12 volt jumper on the positive side of the coil do these 2 things. First, disconnect the other leads on the positive & negative sides the coil, except the breaker point lead to the distributor, of course. Secondly, measure the voltage present with just the jumper wire in place & also see what voltage you have present when the engine fires & is running. Another ?....did you make sure the points aren't shorted out to the breaker point plate inside the distributor (usually due to improperly installation) ? Mike


I'll be sure to check all this stuff out....I'm not sure of anything.lol.I'll run the test.see what happened and go from there...will a bad condenser do this kinda thing?points are new but I don't think the condenser was replaced.

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## bajuski (Apr 9, 2004)

No, if condenser was bad, it wouldn't try to run on the crank switch contacts either.


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## vib-E (Jun 21, 2015)

Well went to fire it up...wouldn't start at all...so pulled dist cap off and the points were stuck open and would only close if I pushed by hand.if I turned it over again.points again would stick open...so I gotta get new points

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## s.a.m (Feb 22, 2016)

So the spring is broken on the points? If you don't have a spare set I'd get one to keep on the boat and a spare condenser. Jm2c.


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## sherman51 (Apr 12, 2011)

i'd just go ahead and get the electronic kit and never worry about points again.
sherman


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## CaneCorsoDad (Jun 11, 2017)

Just make sure the electronic conversion has a schematic to allow wiring the shift interrupter to properly stumble the engine


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## firemanmike2127 (Mar 17, 2013)

Any Hall effect or magnetic pick-up will work just fine with the shift interrupter circuit. Mike


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## sherman51 (Apr 12, 2011)

firemanmike2127 said:


> Any Hall effect or magnetic pick-up will work just fine with the shift interrupter circuit. Mike


that was my thoughts. the interrupter works off the shift cable I thought. but I could be off base. they have electronic kits with instructions on ebay and probably amazon.
sherman


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## vib-E (Jun 21, 2015)

OK boys...has a cracked block..where can I get a new short block?









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## vib-E (Jun 21, 2015)

And how do I know if its a 2 bolt or a 4 bolt main?can I tell by looking at it?or does it matter?4 bolt main better?

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## s.a.m (Feb 22, 2016)

Buy a long block or a complete engine, might have unseen cracks in the heads, doesn't matter that much on two or four bolt main, if leaving stock


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## KaGee (Sep 8, 2006)

Let me see if I can look up the place I bought mine from... a marine re-builder out of Miami and they didn't want the old block back. Several on I-Boats bought from him. 

All the work you have done, how did you miss that?


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## KaGee (Sep 8, 2006)

vib-E said:


> And how do I know if its a 2 bolt or a 4 bolt main?can I tell by looking at it?or does it matter?4 bolt main better?
> 
> Sent from my Z963VL using Tapatalk


Year specific.


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## vib-E (Jun 21, 2015)

KaGee said:


> Let me see if I can look up the place I bought mine from... a marine re-builder out of Miami and they didn't want the old block back. Several on I-Boats bought from him.
> 
> All the work you have done, how did you miss that?


1998 i do believe...how did I miss that..well after the neighbor told me he didn't winterize it.I started checking compression.looking at the block.well there it was.....remember this is the same boat I put heads on last year...all the work I did...gone...hope the heads are still good.and everything else at least...he said he though it be OK in a heated garage.well the power was off for a cpl days last winter and I guess that's all it took...

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## s.a.m (Feb 22, 2016)

KaGee said:


> Year specific.


Only thing that would mess him up would be two or one piece rear main seal as they have a different flywheel


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## sherman51 (Apr 12, 2011)

vib-E said:


> OK boys...has a cracked block..where can I get a new short block?
> 
> 
> 
> ...


I would check out Michiganmotorz.com for rebuilt and new. they was awesome when I replaced my motor.
sherman


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## vib-E (Jun 21, 2015)

I got the block number if anybody can find more on the 2 bolt 4 bolt main...14093638 I been looking but can't come up with any for sure....found a short block if everything comes up

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## s.a.m (Feb 22, 2016)

Need the stamped numbers from in front of the head on the block, even number side of block(#2 cyl.) Flat spot sticks out further than the head. Usually three letters and three numbers


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## backfar (Sep 24, 2014)

Look at the akron craigslist under boat parts, a guy in canton sells mainly sb chevy marine engines at very reasonable prices with warranties, no doubt he would sell just a short block, i got a rebuilt engine from him 2 years ago and its been running as it should.


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## sherman51 (Apr 12, 2011)

vib-E said:


> And how do I know if its a 2 bolt or a 4 bolt main?can I tell by looking at it?or does it matter?4 bolt main better?
> 
> Sent from my Z963VL using Tapatalk


a 4 bolt is just better at holding together at higher rpm's. if its a marine it should have 4 bolt. I bought the new complete motor for my boat from Michigan motorz and even let them install it. I kinda lucked out on mine. its an 86 but already had the newer fly wheel. took it to them early one morning and towed it home that afternoon with a new 315 hp 350 in it. its a vortec motor.
sherman


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## KaGee (Sep 8, 2006)

KaGee said:


> Let me see if I can look up the place I bought mine from... a marine re-builder out of Miami and they didn't want the old block back. Several on I-Boats bought from him.


https://www.rapidomarine.com/


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## The Highway (Sep 20, 2014)

Just installed a 4 bolt main from summit racing with a decent warranty around 2100 for a long block


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## vib-E (Jun 21, 2015)

Where's a good lifting point at on a motor this size?









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## sherman51 (Apr 12, 2011)

vib-E said:


> Where's a good lifting point at on a motor this size?
> 
> 
> 
> ...


use a short piece of chain and take the front intake bolt out on one side and the back bolt on the other side attach chain and lift in the middle of the chain.
sherman


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## The Highway (Sep 20, 2014)

If you don't have a way to get it up out of there. I tracked down a guy in the neighborhood who had a boom truck which was so nice with a boat that has high sides


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## KaGee (Sep 8, 2006)

I built an A Frame and attached a chain fall to it. Lifted the engine out, pulled the boat out and set the engine down on a work stand.


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## vib-E (Jun 21, 2015)

sherman51 said:


> use a short piece of chain and take the front intake bolt out on one side and the back bolt on the other side attach chain and lift in the middle of the chain.
> sherman


Thanks...I was wondering that.if that was a good lifting point putting bolt thru chain and bolting back in where exhaust manifold was bolted...or as u said the intake bolt holes be better...as for lifting I have the means to lift whatever at work...crane.trackhoe.mini hoe.loader bucket.

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## sherman51 (Apr 12, 2011)

vib-E said:


> Thanks...I was wondering that.if that was a good lifting point putting bolt thru chain and bolting back in where exhaust manifold was bolted...or as u said the intake bolt holes be better...as for lifting I have the means to lift whatever at work...crane.trackhoe.mini hoe.loader bucket.
> 
> Sent from my Z963VL using Tapatalk


just go slow and take your time and you'll be ok.
sherman


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