CVX-18 starts when cold, won't start when hot?

[Villager19]

Hi everybody,

I saw Neutron68 posted a thread here a couple of years ago for his boat. (Which I hope is still running great!) My CVX-18 is stock, from what i can tell, Mercruiser 5.0/228 with the Q-jet 4-barrel carb and alpha outdrive.

The sticker on the boat expired in 2015, and i dont believe it was used at all for several years before I bought it at the end of last year. I had the chance to run it at the end of the season last year and it ran awesome! It did stall regularly when shifting gears (more in that later) but that was the only issue. I got a recommendation foe a good mechanic and had it winterized and stored.

Over the memorial day weekend, I took out my CVX-18 for the first time this season. On Friday night it ran great except it would stall when taking it out of gear, but it always started up again. We got it up to operating temp and boated for a while with no other problems.

Saturday morning it started up fine, and we ran it for about 10 to 15 minutes out on the lake. It got up to operating temp and ran great. Tied it up at the pier and it wouldn't start again! Not even hours later.

My mechanice had recommended a change from points to an electronic ignition, which i approved. Thinking this was part of the problem, I discovered that the ignition coil was extremely hot - you could cook an egg on it! It heated up like that even just from cranking the motor.

I actually found an auto parts store that was open and had the same exact coil in stock. I replaced the coil but no luck starting the boat, even though it had not run for 7 or 8 hours.  I guess you could say the motor was still warm but definitely not hot. The new coil did not overheat when cranking.

Sunday morning, of course, it started up immediately! I let it idle for about 10 minutes to charge the battery since I had been cranking on it quite a bit the day before. You know where this is going. I turned it off to go inside, planning to come back out and boat... and it never started again. FYI the new coil stayed cool during this idling period.

I brought it back to my mechanic, who is checking the lower shift cable. This may address the stalling when going in and out of gear as experienced Friday night, but would it have any effect on hot starts?

He is also replacing the ignition switch, which had gotten difficult to get the key in... but I dont think that would impact hot starts. Thoughts?

One thing I noticed: Water was coming in to the engine compartment, right near the top of the outdrive. This boat sits low in the water,  as you all know. My mechanic thinks a bellows needs to be replaced. I doubt this would impact hot starts, but any comments are welcome.

I mentioned the possibility of hydrolock to my mechanic, and he suggested installing an open exhaust boot. What is that? Would this boat normally have one, and if not, would adding one impact performance?

I think the carb was getting fuel, because when I pushed down on the accelerator pump manually, gas squirted into the carb immediately. Is there some sort of cut off switch that could be going bad?

 I like my mechanic and he said he is going to check over everything, but I know this is not the type of boat he has a lot of experience with. And you all know how a boat can run great on land, but not
.. in water! Lol  He does not really have a way to water test it.

Any suggestions on things to check would be appreciated.

Happy Tuesday!!

[Plugcheck]

First off, sorry to hear your having trouble, not an unusual condition given the vintage of our beloved craft.  The first thing to check is the ignition interrupt.  The alpha drive uses dog clutches, and the engine ignition is cut off when shifting to reduce wear.  Cable alignment has been discussed thoroughly in past threads.  You can jumper it for testing, but only temporarily.   Assuming all that is correct, an upgrade to electronic ignition is a great choice, but to truly get the maximum gains, you need a coil matched to the new system, not the old.  Next would be to check the supply voltage to coil, many stock coils use a ballast resistor to limit current.  If you could needs one, but it was removed, then that would explain why the coil got hot.  Is the coil mounted firmly to the engine?    A coil is nothing more than a transformer, the other wire on the output side is bonded to the case.   Next would be fuel checks, but not starting hours later seems more ignition related.  You also stated your ignition switch is troublesome?  Could be a problem not supplying power adequately, not very expensive, I'd opt for changing it.  Hope this helps, Michael.

[Villager19]

Thanks plugcheck!  I will run these questions past my mechanic tomorrow and report back.

[dorelse]

I had a similar condition on my CVZ-18.  It turned out the choke had failed, so it'd start great when cold, then wouldn't when hot.  Let it sit and cool off, it'd start again. 

[Glastronjohn18]

Next would be to check the supply voltage to coil, many stock coils use a ballast resistor to limit current.  If you could needs one, but it was removed, then that would explain why the coil got hot.  Is the coil mounted firmly to the engine?

Just to add to Mike's post. On my CVX 18 with a 228 the wire to the coil in the factory harness is a resistance wire. That gives you the ballast resistance. This wire can go bad. On another note some coils have built in resistance and do not need an external ballast resistor but that would be stated on the coil, box or instruction sheet.
You seem to have multiple issues so take one at a time. Make sure you have power at the coil and check the points gap if you still have them. The condenser needs to be checked. It may be shorting out when hot or now it may be completely shorted not allowing a start at any time. Than as mike said check the shift cut out switch. it needs to have continuity when closed. Shift cable wear and/ or adjustment will affect it's operation. There is also an adjustment as to how much movement it takes to close the switch. The switch is mounted on the shift plate at the rear of the motor so it sees lots of heat and if it's failing heat doesn't help it. The switch is NLA new but I've seen used ones on ebay for about $40. The old switch is superseded by a complete shift plate assembly and switch. This makes more sense than buying a used switch.
The old coil may have had an internal short ,With the new coil not heating you may have resolved that issue.
 there is also a neutral start switch on the throttle control that needs to be checked.
Good luck on finding these gremlins.

[Villager19]

Thanks everybody! It was a loose wire at the throttle control - my mechanic found it. He did some other work that i will start a different thread about. He did an amazing job!

I did get a credit back on the ignition coil that was overheating.

Got out on the Illinois River today and the boat ran so smoothly. Its a beautiful machine 😍

[Plugcheck]

Love to hear all is well now.

[Villager19]

Hi everybody!

Not to revive a super-old thread, but check it out: I think I may have just burned up a second ignition coil, and I am looking for some advice.

As a reminder, my old mechanic, who has since retired, took out the points in 2019. The new ignition system sported a PerTronix Flame Thrower ignition coil, 1.5 Ohm. That one went bad, as previously noted in my post from June 2019. It was just burning up, extremely hot. I believe I may have had two problems back then - a loose connection and also a bad coil. My mechanic found and fixed the loose connection and I replaced the PerTronix with an identical one I bought at an auto parts store.

Flash forward to 2021: my CVX-18 ran great all day Saturday. I shut it down for a few minutes on a break before our evening cruise, and it would not start again. Just like in 2019, the ignition coil was extremely hot. Too hot to touch. The motor would turn over, but just would not fire.

Since they were open on the 4th of July, I went in to O'Reilly Auto Parts store and bought an Edelbrock igntion coil, 1.4 Ohms: https://www.oreillyauto.com/detail/c/edelbrock/ignition---tune-up/ignition-coils/ignition-coil/90c5da72ae86/edelbrock-canister-coil/edb0/22739

The boat started right up with the new coil. It ran for the rest of the weekend, but it is bogging down and it needs to crank for a long time before it starts.

A couple of questions - do I have the right ignition coils here? Bad luck? Or some other issue?

Note that my new mechanic recently adjusted the timing from 16 degrees to 8 degrees. He said it was too far advanced and that a side effect could be running too hot and burning things up. He warned me that I could see a loss of power and I can confirm that it does seem to have lost some power. Is this a related issue?

One other thing I noticed while trying to troubleshoot the ignition problem - there was a loose purple wire up by all the other wires there on top of the motor. I am under the impression this may go to an electric choke, which this carb does not have. Thoughts/comments on the purple wire?

[carlsoncvx18]

With the pertronix you need a minimum of 1.5 ohm coil higher resistance is ok. Wonder how it is wired there should be a slave solenoid that gives the coil a 12volt for start then when go back to run it runs through a resistor wire.  Set your timing at 10 to 12 degrees I run all mine at 12 btdc. 

[Plugcheck]

Most of the early pertronix drop in points replacements were ok with the stock coil rated for points.   If it required ballast resistors, you kept them in place.    Some manufacturers opted to supply full 12vdc during cranking, then when running passed ignition current through the ballast resistor.    This provided hotter spark while cranking.    The pertronix three is a bit more special, has a programmable rev limiter, and can handle coils with 0.3 ohm primaries.    It does so by varying the dwell time, an aspect called adaptive dwell.   The coil getting hot is a problem, possibly a bad coil or wrong part.   Very few aftermarket coils require ballasts.  Is the coil securely mounted to the engine?   Not only is this a heat sink for the coil, it is the secondary coil tie to ground.     The purple wire is switched ignition power, and given it's location, probably fed an electric choke.    If not using it, just insure it's well insulated.   It could short power to ground and cause issues.     One last thing is the ignition cut off Switch on the shift linkage, they kill the ignition when shifting to be softer on the drive going into gear.   They do fail, but more often just need some alignment.   

[Villager19]

True story: I had some warranty work done on my Chevy Silverado a couple years back. The mechanic never fully attached the #1 cylinder spark plug wire, and it ended up burning out the coil for my #1 cylinder.

I was reading up on ignition coil failures over the weekend. Time and time again, articles mentioned worn spark plugs or worn spark plug wires as common causes for ignition coil failure.

It turns out that the #3 spark plug wire on my CVX-18 was just hanging off the plug - it was not clipped on, just hanging there by the boot. When I grazed it with my finger, it fell right off. This is probably been why the coils are burning out, and why the motor has been so hard to start.

Wouldn't you know it, the motor starts and runs so much better with all 8 cylinders??

My neighbor asked me how long the motor could have been like this, and the answer is who knows? Maybe 2 years, since the ignition was changed over? That's when I burned out my first ignition coil, and the boat has been difficult to start the entire time. Sadly, I brought it back to him and he could not diagnose the problem, even though he knew the coil burned up after he did the work. I guess he is retired now, lol! We kind of just chalked it up to a bad part.

Also sadly, my new mechanic who recently adjusted the timing on the motor and did all kinds of work with my spring startup did not catch this. They would have been right there at the #1 cylinder, right? Were they checking their work, or checking close enough for other problems? You've got to lol about this stuff, I guess. Nobody is perfect, right? 

One takeaway: sometimes we should start with the basics.

Yet another takeaway: learn as much as you can and DIY, especially on these vintage boats.

Plugcheck - I did insulate and secure the purple wire. Thanks for the suggestion!

Just so that I am more confident in the ignition system, I am going to replace the plugs and wires. Are there any recommendations on plugs and wires out there?

Here is the ignition coil that was installed with the conversion from points, the PerTronix 40011 Flamethrower. I burned up the original and then a second one: https://www.summitracing.com/parts/pnx-40011

I'm thinking about installing the epoxy-filled version now - any thoughts? https://www.summitracing.com/parts/pnx-40111

Here is what I picked up and ran on an emergency basis. I've run it for about 2-3 hours so far, seems OK, but comments are welcome: Edelbrock 22739 - Edelbrock Max-Fire Ignition Coils https://www.summitracing.com/parts/edl-22739

This is the conversion kit that was used, the PerTronix ML-181 - PerTronix Ignitor® Solid-State Ignition Systems: https://www.summitracing.com/parts/PNX-ML-181 Given the coi l issues, should I be replacing this, too? And is it even meant for marine applications?

Lastly, any recommendations on a cap and rotor? I'm really just wanting to start from scratch so that I know what's going on. Thanks in advance!