1966 McCullouch 7.5 stumbles but wont run

[rtwoolums]

I have a 1966 Mcculloch 7.5 HP outborad I am trying to get running.

When I pull the starter rope the engine stumbles alittle but will not run. I am thinking the carb might need to be rebuilt but wouldnt mind hearing other opinions. I tried putting some fuel mixture directly in the cylingers with the same result. Spark plugs are new but I have not replaced any of the other ignition pieces yet.

There are 4 machine screws that holds the ignition system to the to top of the motor. I can get 2 of these screws loose but the other two seem to frozen. I have tried soaking them with WD-40 but still cant get them loose. Any suggestions on getting them loose? I cant get the carb off to rebuild it without removing the power head so I need to get these screws loose.

Thanks

 

[Tom @ Buzzard Bluff]

Re: 1966 McCullouch 7.5 stumbles but wont run

I have a 1966 Mcculloch 7.5 HP outborad I am trying to get running.

When I pull the starter rope the engine stumbles alittle but will not run. I am thinking the carb might need to be rebuilt but wouldnt mind hearing other opinions. I tried putting some fuel mixture directly in the cylingers with the same result. Spark plugs are new but I have not replaced any of the other ignition pieces yet.

There are 4 machine screws that holds the ignition system to the to top of the motor. I can get 2 of these screws loose but the other two seem to frozen. I have tried soaking them with WD-40 but still cant get them loose. Any suggestions on getting them loose? I cant get the carb off to rebuild it without removing the power head so I need to get these screws loose.
Thanks

You need an 'impact screwdriver', a device that converts a hammer blow to torque to break loose stubborn fasteners. They are available from almost any tool source from Horror Freight to your local auto parts store and you WILL need it when you pull the powerhead to access the carb for the cleaning it is crying to receive.

The ignition systems on this series of motors seems near bullet-proof and all 3 in my collection required only a though cleaning of the entire mag plate (with paint thinner) and polishing the points with gradually finer grades of wet-or-dry sandpaper down to a piece of worn-out 600 grit to remove the invisible insulating 'scum' that accumulates on all points that go unused for a long time. The coils, condensers and plug wires (except for one wire the mice beat me to!) were fine and once the points were cleaned and regapped I have enough blue-white spark to fry meat.

If your motor has been idle a long time plan on sanitizing the entire fuel system from the tank breather vent to the reedplate.

Brian Wilcox (http://www.chrystine.com/impellers/order.html) can make new impellers for you but will have to have the brass liner from your old ones.
HT, Tom

 

[rtwoolums]

Re: 1966 McCullouch 7.5 stumbles but wont run

Thanks Tom,

I see Lainge's Outboard has a gasket for the Tellitson AJ carb and a kit for the Tellitson OM carb. Any idea how I can tell which one I have on this motor before I tear it down?

 

[Tom @ Buzzard Bluff]

Re: 1966 McCullouch 7.5 stumbles but wont run

Thanks Tom,

I see Lainge's Outboard has a gasket for the Tellitson AJ carb and a kit for the Tellitson OM carb. Any idea how I can tell which one I have on this motor before I tear it down?

Unless someone has retrofitted it with a Tillotson it should have the Marvel-Schebler SUM carb on it. Only the very earliest 'Fishing Scott' versions of the Lo-boy bore the Tollotson diaphragm carb.

AFAIK there are NO parts available for the M-S. I just cut a new fuel pump diaphragm to replace the one eaten up by time and gasahol for my '64 model which is once more purring like a contented kitten. 'Ollie' on the Oliver outboard site stocks it.<http://www.pfs-ware.com/Parts/OllieParts.htm> A piece exactly large enough to slip into a standard business size envelope will set you back @ $15 but is big enough to make3-5 diaphragms if you have a steady hand with Exacto knife and scissors. HTH, Tom

 

[rtwoolums]

Re: 1966 McCullouch 7.5 stumbles but wont run

Thanks once again Tom,

I took another look and I did see the Schebler plate on the carb. Guess I will get an impact screwdriver this weekend and try and tear this thing down and see what I got.

Thanks Again