12HP Sea King acting funny

[mr-asa]

Getting this motor up and running for my brother for a Christmas present. 1958 12HP Sea King, 12S13

Disassembled everything but the powerhead, cleaned it all, put it back together, checked the ignition system and only found the condensers to be be lacking. Disassembled the carb and soaked it in Chem-Dip carb cleaner for a solid week, rebuilt it and set everything to the base specs in the Gale book I got when I was first playing with my 12D10. I believe it called for the high and low speed jets to be 3/4 of a turn out, I thought this might be low, but this book hasn’t steered me wrong yet.

Engine won’t run except at WOT. Now, she runs great at WOT but as soon as I try and adjust the carb she starts spitting and coughing and dies. Then I have to adjust everything back to where it was in order for it to even start again.

Thoughts?

[beerman57]

About any OMC motor initial needle settings will be 3/4 turns out from lightly closed for the high speed and 1.5 turns out for the low speed. I’m sure you blew it out good with compressed air, I’ve been having some needle packing washer issues lately, and it acted about like yours.

[mr-asa]

Hrm. I’ll try swapping them out.

[frankr]

12S13 is a 1957. Nevertheless, the link rod between the cam follower and carburetor—does it have more than one hole in one of the levers? If it does, putting it in the wrong hole can really mess up they sync.

[mr-asa]

quote FrankR:

12S13 is a 1957.

It seems like everything I have is a ’57 or a ’58. I can never remember which engine is what year.

I believe it does have two holes. One of the linkages has a slight crack so it doesn’t tighten straight as well (hard to explain, I’ll try and get a pic later)
I’ll go through the disassembly pictures and make sure I have that hooked up properly.

[mr-asa]

Still messing with this. Turned out I had a bad gasket which was letting in a fairly severe air leak that was messing me up.
Now that that is fixed, however there’s still something strange going on. I checked the linkage rod and made sure that at stop the throttle plate was all the way closed and at WOT it was all the way open.

Strangely enough, at WOT, adjusting the low-speed needle gives me more results than the high speed needle. There is a little bit of a sweet spot that lets me get the motor down to about 3/4 throttle from WOT, but outside of that spot I have literally no adjustment.

The low-speed needle does seem to like being adjusted out 1.5 times, while I can’t seem to get any real changes from the high-speed.

[frankr]

There must be something funky about that high speed needle. If you were to screw it all the way in, it should completely cut off ALL fuel. As you screw it back out,it rapidly opens the flow path, even to extreme. Somewhere in there it must be "right". In other words, I don’t see how it could not be doing anything. Unless of course it isn’t actually going all the way in if you try.

[mr-asa]

The needle looks ok, no real damage to it I can see. When I had the carb apart and the cap that you hammer in out of the body, I neglected to see if the needle screws all the way in, but it feels like it is. There is a definite stop at the bottom of the needle’s adjustment.
If I screw the needle in all the way except for the last maybe 15-20% I’ll see a little change, but nowhere near what I would expect to see with that much adjustment.
The fact that I see a change in running with an adjustment in the low speed is really throwing me off

I blew out everything, and while the carb wasn’t bad this motor was fairly crusty, I’m starting to wonder if there was actually corrosion in there I didn’t see. Ever run into that type of issue?

[Anonymous]

is the carb flooding a little?

[mr-asa]

I’m not seeing any flooding. How can I tell?

[Author]

Posts