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KFL won't start after it sits for 20 mins

Your old Chris-Craft electrical system can be a challenge. If it runs on "juice" pose your questions and offer your advice here.

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L76
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KFL won't start after it sits for 20 mins

Post by L76 » Wed Jun 29, 2022 10:15 pm

Hi All!

I posted this in the engine section too... but this might be an ignition issue, so... posting here too for some sage advice. Thx!

Boat runs fine (3,000 RPM on Lake Tahoe @ 6500 feet elevation)... but after I shut it off for 20 mins (or more)... it won't start. I eventually get it back running (after alot of fussing with choke/throttle... 20 mins of frustration... and *GULP* actually pulling the plugs and dropping some fuel in the chambers). Once it is back running my engine power is cut so bad that I can only achieve 1400-1600 RPMs. Not fun.

BOAT = 1948 CC Deluxe Runabout with KFL 131hp motor and 2 Zenith carbs. Stock ignition with points. Problem happens every time I take it out. Rebuilt carbs, fuel pump, aligned linkages, cleaned out the entire fuel delivery system, and messed with ignition timing. The problem has happened pre (and post) carb rebuild. Pre (and post) fuel pump rebuild. Pre (and post) ignition timing adjustments.

I am flummoxed. Thoughts?

Cheers,
Dennis - L76
1948 Chris-Craft Deluxe Runabout
Spends her time in Tahoe

brian.david.roberts
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Re: KFL won't start after it sits for 20 mins

Post by brian.david.roberts » Thu Jun 30, 2022 12:41 am

Just a wild guess... Vapor lock? Not sure if it can happen on older boats like these, but I was having a similar sounding issue with my newer fuel injected ski boat. Might could try pouring cold water around the carb bowl area and see if the issue goes away?

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Bilge Rat
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Re: KFL won't start after it sits for 20 mins

Post by Bilge Rat » Thu Jun 30, 2022 9:24 am

Might be related to today's gasoline formulation for fuel injection engines and the higher elevation of Lake Tahoe. Gas is formulated for easier atomization required for fuel inject engines and is not what a carburetor wants. After shutdown, it is probably boiling away in the carbs and starving the engine. Are you running non-ethanol high octane gas? Do you see full gas in the pump bowl or just bubbles?

Might also be a fuel pick up problem in the tank like a pin hole in the suction line. Temporarily running from a gas can instead of the tank might point to that.

You may want to talk with the guys at Sierra Boat on Tahoe about it as they may be familiar with this problem at the mountain elevation.

Not sure if you've tried this but replace the ignition coil and condensor.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

L76
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Re: KFL won't start after it sits for 20 mins

Post by L76 » Thu Jun 30, 2022 1:49 pm

Thx guys. FWIW… there is no resistor on the coil. Just direct wire to ignition and distributor.
1948 Chris-Craft Deluxe Runabout
Spends her time in Tahoe

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Bilge Rat
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Re: KFL won't start after it sits for 20 mins

Post by Bilge Rat » Wed Jul 06, 2022 8:46 am

Just an FYI, the condenser is a small metallic capacitor usually inside the distributor or for older ones, strapped to the outside of the distributor body. They do go bad and replacement is cheap.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

L76
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Re: KFL won't start after it sits for 20 mins

Post by L76 » Wed Jul 06, 2022 10:07 am

Thx Bilge Rat.

I am actually a bit of an "engine guy." Just new to Chris Crafts and this new (to me) 1948 CC Deluxe Runabout (KFL motor). I served as an apprentice in my father's Flathead Machine shop for years. I've been building Bonneville Salt Flats racing flatheads (Ford and Mercury strokers, blown, fuel injections, Arden heads, you name it, etc.) with my dad for years. Just never worked on one of these Hercules inline 6's... not too many car guys are racing tractor engines. ;}

I eliminated the condenser/ignition as the issue and eventually resolved that this was a fuel pump/2nd (back) carb issue.

I am still not happy with the performance of this motor, but I know I do not have it dialed in yet. I may never be happy with the performance - and if I cannot get it where I want it - I am prepared to install something that will. I have a few 250hp+ V8 flatheads on standby. ;}

What should I expect for a "good performing" KFL? I am running my boat on Lake Tahoe (elevation 6500 ft. and sometimes water can be a little rough), I would like to be able to haul 4-5 passengers + a cooler (e.g. 600 lbs to 750 lbs of cargo) in this little 17' Deluxe Runabout at a good cruising speed (e.g. can I get her at 3200 rpm with this load)? What is a good cruising speed/RPM? How "should" I run her?

Cheers,
L76 (Dennis)
1948 Chris-Craft Deluxe Runabout
Spends her time in Tahoe

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Bilge Rat
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Re: KFL won't start after it sits for 20 mins

Post by Bilge Rat » Wed Jul 06, 2022 1:39 pm

Sounds like you have extensive knowledge in engine work. You're right, not many tractor engine races, excepting the crazy high performance tractor pulls that most times end up in blown up engines.

I used to own a 1955 17 foot Sportsman with the KLC 131 HP engine. I never boated at higher elevations, but in the St. Lawrence River, that was enough horsepower to carry 4 adults and tow a skier after a total engine rebuild. Up at Tahoe level, I'm sure a modern V8 would be better, but I ran the KLC at about 3000 RPMs and it was happiest around there.

FWIW: I am restoring a 22 foot Sportsman and am still dialing in a rebuilt MCL dual carb 175 HP engine. I have previous dual carb experience with British cars, but still haven't found the sweet spot balance point for this monster.
1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

L76
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Re: KFL won't start after it sits for 20 mins

Post by L76 » Thu Jul 07, 2022 12:38 am

As I’m starting to go through it… found I have 90lbs on all holes except for cylinder 2 (70 lbs). I retorqued the head to 85lbs/ft (found a few loose nuts near hole 2)… but it’s still only 70 lbs in that cylinder. Concerned I’m chasing my tail… and will end up pulling the motor and putting it in my test harness. Hard to dial in ignition timing when there’s no easy marker for TDC and my timing light! Given the low pressure on hole 2… that head may be coming off soon anyway!

Cheers,
L76
1948 Chris-Craft Deluxe Runabout
Spends her time in Tahoe

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drrot
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Re: KFL won't start after it sits for 20 mins

Post by drrot » Thu Jul 07, 2022 9:00 am

A KFL should have a timing marker at about 1 O'clock between the two bolts that hold the front flange to the block. Matches to a dimple on the flywheel.
Jim Staib
www.finewoodboats.com


1947 Penn Yan 12' Cartopper WXH474611
1950 Chris-Craft 22' Sportsman U-22-1532
1957 Chris-Craft 26' Sea Skiff SK-26-515
1968 Century 17' Resorter FG-68-174

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