rough running Chrysler

[AtlDawg]

WEll guys,<br />I got my 70 hp Chrysler (707HF) mounted and now it's running rough. I checked and reset dist. timing, took carbs apart and cleaned, got strong spark on all 3 cyl. It cranks, idles smooth for 15 -20 seconds, starts missing and dies. I can idle it up and keep it running but it always starts running rough like it's missing a cylinder after a few seconds. I checked, cleaned and re gaped points, plug and coil wires are good. dist cap and rotor clean and shiny connections. New spark plugs and #1 and #2 a little wet and black, #3 is black and dry. #3 carb bowl was full when I removed it so I assume it's getting fuel. Any thoughts from the experts?<br /><br />Thanks

 

[rbruce63]

Re: rough running Chrysler

I would first check compression on all cylinders. According to the Clymer's manual it should be from 145 to 155 psi. Secondly, if the compression seems within the limits I would syncronize timing, carburetor syncronization and throttle pickup which is the proceedure that the shop manual calls for. Finally, if this strategy fails, then I would overhaul the carburetors.<br /><br />The original shop and parts manual for your model of motor can be purchased from http://www.hurrikain.com/ChryslerMarineStore.htm and a Clymer's Chrysler Outboard Shop Manual could be useful in approaching this out of tune problem in a rational way.

 

[AtlDawg]

Re: rough running Chrysler

Compression is good, 135 on all 3 cylinders. I took off the dist to check and clean the points and reset timing according to the manual. Already took carbs apart and cleaned, adjusted. Throttle linkage seems right according to the manual as well. I'm stumped...

 

[rbruce63]

Re: rough running Chrysler

Rough Operation is caused by the following:<br /><br />"Dirt and water in fuel.<br />Reed valves open or broken.<br />Incorrect fuel level in carburetor bowls<br />Loose carbureters at mounting flange<br />Carbureters not correctly assembled<br />Low fuel pump pressure (replace the diaphragms)."<br /><br />In your case the spark plugs with black sooty deposits might point to an overtly rich condition.<br /><br />I think the next step would be to check the fuel pumps and carburetor floats level.

 

[rbruce63]

Re: rough running Chrysler

Also, have you checked the operation of the choke lever or choke shutter sincronization? Perhaps one or two of the carbureters remain choked while the other is not adjusted and is running rich.

 

[The Marine Doctor]

Re: rough running Chrysler

When you say strong spark..how strong? All 3 cyl's 1/2 inch consistantly?<br /><br />When the engines start to get tired they need a stronger spark. <br /><br />If you have the original coil it may be misfiring. There is an updated coil that performs much better.<br /><br />With the weak coil the engine will load up on fuel until such time as it air/fuel mixture gets fired by the exhaust as it passes the cyl on its way out. This will cause the engine to idle and run rough.<br /><br />TMD

 

[AtlDawg]

Re: rough running Chrysler

I found the spark plug wires out of sequence. 2 and 3 were swapped. It's amazing that it would idle as smoothly as it did that way, other than the intermittant miss. Purrs like a kitten when they are on there right. I think all the other stuff I did, cleaning carbs and setting the timing helped. Thanks to everyone who offered assistance. I owe you guys a beer!

 

[AtlDawg]

Re: rough running Chrysler

Also, when cleaning the carbs, the floats didn't quite fall to horizontal when turned upside down. I know the book says 13/32 but isn't horizontal a good way to set them?

 

[The Marine Doctor]

Re: rough running Chrysler

You will have decent luck with Horizontal.<br /><br />TMD

 

[rbruce63]

Re: rough running Chrysler

Good to hear that you have your Chrysler working smoothly. <br /><br />I would be a little concerned with the compression which is below normal for this motor according to Clymer's. <br /><br />You could start thinking in replacing the piston rings and this could help increase the compression a bit.

 

[scotiany]

Re: rough running Chrysler

AltDawg, the following is from the Seloc manual. It deals with compression checks. " a variation between the readings is far more important than the actual reading, especially for older powerheads". Should put your mind at ease.

 

[AtlDawg]

Re: rough running Chrysler

I checked the compresson again today. This time I warmed it up and left the throttle wide open and got 140 on all 3. Used 2 cans of Sea Foam and man was it dirty. The engine idles and refs great but agian at the lake today, will not accelerate. When I throw the throttle it starts to go and then holds at 2000-2500 rpm like it's bogging. I wonder if I hae two much boat for this engine?

 

[AtlDawg]

Re: rough running Chrysler

One more thing that may or may not be related. My regulator stopped charging a while back. I took the wires from the stator off the regulator and it only shows 60 volts when throttled up. That sounds like it's too low. I have another regulator on the way but this would be 3 in the past few years. Maybe the stator is causing some/all of my problems?