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Posted on Tuesday, December 10, 2002 - 12:07 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)


Hello Andrew,

these pictures show what I received from Newfoundland. I'm looking for information on the fuel and firing sequence to assist me in figuring out what might be missing on the trip mechanism at the top of the head area.

Feel free to post any of these on the discussion board, etc. of the oldmarineengine.com web site.

Bob McLeod
New Brunswick, Canada

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Dick Day
Posted on Tuesday, December 10, 2002 - 07:17 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)


I think you want to be careful regarding your Lathrop. I expect you may find the head studs are 1/2"-12thread not 1/2"-13 thread. Some people have in the past made new studs that have 12 thread on the cylinder end and 13 thread on the nut end. I see you have a water heated inlet check valve on the carburetor inlet. What size pipe thread is the carburetor inlet side of
the check valve? The way the check valve was heated was to pipe the warm cylinder discharge water through the check valve water jacket and then over the side or down the exhaust pipe to cool and quiet the exhaust.

The igniter seems complete. The vertical lever is a quick change on the spark advance from retard to normal running advance.

J.W.Lathrop for some reason never believed in mixing oil in the gasoline. His customers did fortunately. The stupid pump on the crankcase was intended to give a shot of oil to the big end of the piston rod when starting the engine. You should find a one 1/8th inch pipe plug or perhaps just the female 1/8th inch threaded opening low down on the cylinder wall just below the water jacket on the starboard side to allow the double drip oiler to feed the piston skirt. If it is through the water jacket area then there is a dome headed hollow (pipe threaded) brass rod that conducts the oil through the water jacket to the cylinder wall to lube the piston. There is another in the forward face of the forward bell housing on the starboard side. This was fitted with a right angle 1/4 " brass compression fitting which connected to the double drip oiler high on the cylinder wall with copper tubing. The portion that screwed into the bell housing had a short length of copper tubing soldered into it. (about an inch long) This tubing dripped oil into the slinger ring around the crankshaft which fed the crankshaft piston rod bearing. In theory at least. The scheme was very unreliable and mixing oil in the fuel was the only safe way to protect the inside of the engine. Kerosene and oil don't mix well and you would have to use this scheme if you wanted to burn kerosene and a few did but most stuck to 40:1 gasoline (regular) to 1 pint of SAE 30 non detergent oil. Repeat non detergent oil. Don't use modern 2 cycle oil as it is formulated for high temperature burning and high swept piston speeds. Chain saws and weed whackers are a good example of the type equipment that type oil is designed for. It won't hurt these old timers but it such can mess them up with carbon and oil coming out the exhaust pipe. Don't add more oil to the mix as you will only make the combustion chamber carbon up faster than they already do. Most of these engines in daily service would have the carbon
cleaned out of the upper chamber and exhaust port and exhaust pipe on a yearly basis.

I note the pull out handle for starting the engine is missing. The flywheel outer face of the rim is notched so it is easier to grab for a "Rock" to start. The typical watermen procedure was to "STOMP" on the flywheel spoke in the direction opposite you wanted to run. In this mode the spark is retarded with the quick change lever. The engine backfires and runs in the opposite direction. You could then advance the spark in the running direction. Keep in mind an eccentric drive ignition system doesn't know which direction the engine is running. A geared timer drive or swing arm style ignition system knows which direction the engine is running. Some people would leave the lever in the advance spark position at the risk of an early flywheel kick back. So many people were injured with the pull out type starting handle that some maker stopped supplying them on their engines.

The extended shaft aft of the bell housing was probably for a pot or net hoist with the reverse gear aft of that. This allowed the use of the engine for pot or net hauling with the reverse gear in neutral. Best guess I can make on that feature as most bob tail engines had much shorter tail shafts than yours. It could be the residue of a built in reverse gear. Most of these I have seen would have a pair of approximately 3" right angle steel supports with the engine beds bolted to them with them extending aft of the engine to support the reverse gear. The angles were in turn bolted to the beds in the hull. In this case the tail shaft would have been a little longer to support the "sun" gear of the reverse gear but not as long as this engine's tail shaft appears to be.

Use heavy water pump grease in the grease cups. Don't use modern wheel bearing grease. Too Thin!!!. Twist 1/4 to 1/2 turn every half hour to one hour when in operation.

Best I can do on short notice.

Regards and Merry Christmas,

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Richard Day
Posted on Wednesday, December 11, 2002 - 09:29 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

I forgot to add the 40:1 fuel oil/mix is one pint oil to five gallons of gasoline.
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Posted on Monday, March 06, 2006 - 04:41 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

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