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Engine bogs down past 2,100 RPMS

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joesoboti
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Engine bogs down past 2,100 RPMS

Post by joesoboti » Sat Aug 11, 2018 4:42 pm

MCL 175 timing is spot on, idles smoothly at 500 RPMs, under load accelerates smoothly and steadily up to 2,100. Past that it seems to bog down and choke through 2,700. It will not go past 2,700. Without load, the engine will rev all the way up smoothly. Carbs have been synchronized with a pressure gauge. Any thoughts?
Joe
Joe

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mbigpops
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Re: Engine bogs down past 2,100 RPMS

Post by mbigpops » Sat Aug 11, 2018 8:21 pm

Timing. I have the same issue with my KL.

Mark
1953 CC Rocket Runabout "Rocket Man"

cc-woodboats
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Re: Engine bogs down past 2,100 RPMS

Post by cc-woodboats » Mon Aug 13, 2018 8:17 am

sounds like either fuel delivery issue or lack of spark at higher load&speed.

krrs
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Re: Engine bogs down past 2,100 RPMS

Post by krrs » Mon Aug 13, 2018 11:06 am

If still running points in the distributor, make sure the condenser is screwed down tight, making a good gound.

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joesoboti
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Re: Engine bogs down past 2,100 RPMS

Post by joesoboti » Mon Aug 13, 2018 11:18 am

Thanks, fuel pump pressure is my bet as well. I'm working on checking that out, not an easy thing to do. As for distributor, its been upgraded to Petronics.

davidvn
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Re: Engine bogs down past 2,100 RPMS

Post by davidvn » Mon Aug 13, 2018 10:45 pm

Joe drain back both of your carburetors through the main jet plug which is on the back of the carburetor pointing about 45°. You’ve had this problem before and one of your carburetors more than likely has dirt in the main jet

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joesoboti
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Re: Engine bogs down past 2,100 RPMS

Post by joesoboti » Tue Aug 14, 2018 3:36 pm

Thanks David.

jfrprops
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Re: Engine bogs down past 2,100 RPMS

Post by jfrprops » Tue Aug 14, 2018 7:23 pm

you say you have petronics….but if you left a coil resistor inline....and it has burn through....those are the symptoms?????

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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tkhersom
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Re: Engine bogs down past 2,100 RPMS

Post by tkhersom » Wed Aug 15, 2018 6:22 am

Interesting thread!
I am having a similar problem with an MCL and I have changed to Pertronix ignition. I have been expecting fuel delivery was my problem.
John where do I look for this coil resistor? Should it be removed or replaced?
Thanks guys! :D
Troy in ANE - President CCABC

1957 CC 21' Continental "Yorktown" (Mom's boat)
https://www.chris-craft.org/boats/22625/
1958 CC 38' Connie "American Beauty"
https://www.chris-craft.org/boats/22607/
1985 Formula 242LS "Gottago"
1991 Formula 36PC "Band Aids"

Life Is Too Short To Own An Ugly Boat

jfrprops
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Re: Engine bogs down past 2,100 RPMS

Post by jfrprops » Wed Aug 15, 2018 8:37 am

The coil resistor on older engines is always located near the coil....it is a white ceramic deal about 3 inches long and 1/2 wide and across.....inside it is a coil of wire ( visible on the open back side of the ceramic deal) that acts to reduce the high voltage of starting from burning out the points and etc....but I think it is not needed with electronic ignition...though it may have been left in the circuit and if so when if fails it overloads and leads to the problem mentioned. When you try to accelerate it messes up the ignition....not a likely scenario...but possible and one I have run into more than a few times. You can usually tell if the resistor is broken by looking for burned out place on the wire coil inside it....if that is compromised you are toast).
John in Va
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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mbigpops
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Re: Engine bogs down past 2,100 RPMS

Post by mbigpops » Wed Aug 15, 2018 9:15 am

In this unrestored engine photo it is the white vertical item to the right of the coil. No longer needed with Pertronix.

Mark
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1953 CC Rocket Runabout "Rocket Man"

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tkhersom
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Re: Engine bogs down past 2,100 RPMS

Post by tkhersom » Wed Aug 15, 2018 9:54 am

Thanks guys!

I will look next time I run Yorktown.
Troy in ANE - President CCABC

1957 CC 21' Continental "Yorktown" (Mom's boat)
https://www.chris-craft.org/boats/22625/
1958 CC 38' Connie "American Beauty"
https://www.chris-craft.org/boats/22607/
1985 Formula 242LS "Gottago"
1991 Formula 36PC "Band Aids"

Life Is Too Short To Own An Ugly Boat

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joesoboti
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Re: Engine bogs down past 2,100 RPMS

Post by joesoboti » Wed Aug 15, 2018 10:13 am

Thanks John, I do not have one of those.

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joesoboti
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Re: Engine bogs down past 2,100 RPMS

Post by joesoboti » Wed Aug 15, 2018 8:21 pm

Thanks everyone. I think we have a handle on it. Combination of timing and dirty fuel. Running much better now, up to 2.900 rpms under load.

Badger85
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Re: Engine bogs down past 2,100 RPMS

Post by Badger85 » Thu Aug 16, 2018 2:31 pm

Initially your post indicated timing had been checked and was "spot on"- easy enough to do on an MCL as there is a timing mark. So how was it off? Spark advance not working properly?

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