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Hard to start when hot

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bongocruiser
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Hard to start when hot

Post by bongocruiser » Wed Jul 22, 2015 9:25 pm

My 1942 Special with Model K engine starts easy with the new petronix ignition, new large 6V battery, heavy 6V battery cables, and rebuilt starter. But after it runs a while, if I shut it off it wont start and the battery acts like it is dead. Starts fine after it cools down. I've owned the boat for 40 years and have done all the work so I know the motor well, but it's aways been hard to start when warm. Could the engine be too tight? Suggestions welcome.

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Doug P
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Re: Hard to start when hot

Post by Doug P » Wed Jul 22, 2015 10:23 pm

coil :?:

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evansjw44
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Re: Hard to start when hot

Post by evansjw44 » Thu Jul 23, 2015 6:16 am

I'd guess too tight. Try this. Figure out a way to get a torque wrench on the center of the flywheel. With the engine cold, pull the spark plugs and turn the engine over with the torque wrench to get a reading. The put the plugs back in and heat it up and repeat the test. If its too tight the torque will be much higher. I've seen this before and it turned out to be piston rings that weren't gapped correctly.

You might also have a cooling issue where water flow around one or more cylinder bores is not sufficient to cool it. You might see that with an infrared temp instrument.
Jim Evans

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bongocruiser
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Re: Hard to start when hot

Post by bongocruiser » Thu Jul 23, 2015 7:11 am

That's a great suggestion, I'll put a torque wrench on the flywheel and test it hot and cold.

I'm interested in the coil comment. I had a hard time starting earlier this season, it would need starting fluid and the battery on a charger. I put an old coil back on and it started right up. I was getting spark but a very weak spark. Now I wonder if even a better newer coil could improve it even more. Is there such a thing as a high performance 6V coil or do I just buy a new one at NAPA?

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ClassOf56
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Re: Hard to start when hot

Post by ClassOf56 » Thu Jul 23, 2015 12:14 pm

Coils have a tendency to short out when they get hot, drawing down the battery. Try to find out how tight the motor is at hot. If so, it is a mechanical issue, probably to do with the piston rings not being gapped properly as said previously. If it mechanically turns ok when hot, you have an electrical issue, probably with the starter motor being shorted internally when it gets hot.
Steve A
1956 18' Chris-Craft Continental

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Bilge Rat
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Re: Hard to start when hot

Post by Bilge Rat » Fri Jul 24, 2015 12:40 pm

For a 6 volt coil, there really isn't a high performance version that I am aware of. The only difference I have seen in old type coils is whether a ballast resistor is used or not. I never saw a 6 volt ignition that used a ballast resistor. While you're at NAPA, buy two as coils have a habit of quitting or worse, intermittently quitting and working again (I have been there). I always carry a spare coil on the boat.

As a note, never leave the ignition key in the 'ON' or 'RUN" position without the engine running. If the points are closed in the distributor a lot of current will flow through the coil making it hot and causing issues. We are all so used to modern electronic ignitions in our cars, its easy to forget this when working with old school systems.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

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Bilge Rat
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Re: Hard to start when hot

Post by Bilge Rat » Fri Jul 24, 2015 12:46 pm

Well after re-reading your original post, I see you're using a Pertronix igniter so no points in your distributor. I would have to believe the same caveat about leaving the key in the 'ON' position applies as the igniter would still be conducting depending on the position of the engine.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

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bongocruiser
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Re: Hard to start when hot

Post by bongocruiser » Sun Jul 26, 2015 3:17 pm

Thanks Bilge Rat, I've been fine since I replaced the coil, I'm going to buy a spare as you suggested as it seems to create intermittent issues that are hard to diagnose.

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Bilge Rat
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Re: Hard to start when hot

Post by Bilge Rat » Sun Jul 26, 2015 8:48 pm

True that bongo. My MacGyver skills have been tested with a boat load of guests on a few occasions. Tools and spare parts go a long way to saving the day and your pride.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

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