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Suddenly poor running, KBL

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kenkix
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Location: White Bear Lake, Minnesota
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Suddenly poor running, KBL

Post by kenkix » Sat Jul 02, 2022 2:15 pm

Hi, guys

Overnight, my engine performance got very poor. I mean by this that, without load, the engine revs fine, sounds good. Under load (in forward gear):

-- it won't fully rev (only up to ~3000 rpm)
-- sounds "thumpy" (obviously I'm no mechanic)
-- water flow seems fine

The only thing that has changed is that we stop we moored in a very shallow sandy beach, just deeper than the rudder. I started it on that shallow area and left some divots. If the cooling system got clogged, would it cause poor engine performance? It seems like would just overheat.

Ideas?

Thank you

Ken
Ken
=====================
1950 Special Runabout: "Just for Kix"
Hull# SR17 1349
Engine# KBL 65216

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Captain Nemo
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Re: Suddenly poor running, KBL

Post by Captain Nemo » Sat Jul 02, 2022 4:39 pm

Check and see if you fouled something around your prop or shaft.
Boats are to be made of wood, otherwise, God would have grown fiberglass trees.

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kenkix
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Location: White Bear Lake, Minnesota
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Re: Suddenly poor running, KBL

Post by kenkix » Tue Jul 05, 2022 12:34 pm

Thank you for the suggestion. I had run my hand over the shaft and propeller by that time, but I donned some goggles and got a good look. Now it is on the hard. Nothing impeding the shaft/prop.
Ken
=====================
1950 Special Runabout: "Just for Kix"
Hull# SR17 1349
Engine# KBL 65216

L76
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Re: Suddenly poor running, KBL

Post by L76 » Wed Jul 06, 2022 10:29 am

I'm new to these K motors, but in my experience... this could be ALOT of things... but it always comes back to something basic. As it was explained to me - boat motors are constantly under load (vs. car engines) - so they tend to be more sensitive to any one little thing being "out of line" than a car motor. You'll notice problems when under load (but not when it is in neutral) with even the slighest issue.

Here's what I would check:

1. Distributor cap/rotor/condenser - all working properly? No cracks? Advance springs still functioning properly? Did distributor "move"? (eg - I have found that the lock down on some of these old distributors have become stripped - and thus cannot lock down the distributor's advance setting)

2. Carbs - did any of the linkage (throttle AND choke) shift either carb out of alignment with the other(s)? Fuel or air blocked to one or many of the carbs? (Eg - this could be as stupid as a stuck choke that could have come about when you grounded the boat? I have literally seen a burr in the air horn in one of my carbs bind the choke on one carb while the other operated properly - literally killing power to the back 3 cylinders ... which appeared similar to what you explained ... limited my RPMs to 2000 as the motor could not get the air it wanted from the back carb).

3. More carbs - go through it all... needle and seat, blocked jets, float height settings, gaskets (eg gasket to engine block should seal too!), re-check the linkage and butterfly operation AGAIN.

4. Fuel/air - is the fuel pump, all filters, etc. clean and functioning properly? Are the fuel lines to one (or more) of the carbs blocked? Basically - it's just fuel and air - all carbs need to be able to efficiently deliver both to the motor.

Admittedly - I do not have my KFL running the way I want it at the moment... but I am working through it.

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

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