TOPIC: 1962 Evinrude Starflite V4 75hp, engine is surging

Took my somewhat reconditioned boat out for a shake down cruise yesterday. My boat is a 1960 Dorsett El Rey runabout. About 6 months ago I bought a low hours 1962 Evinrude motor from New York, and had it shipped to my home here in California as a replacement for the original motor of the same year, and model #. After taking delivery I rebuilt the carb, fuel pump, distributor, water pump, thermostat, lower unit, and installed new fuel, and water hoses on the power head before mounting on the boat. I also replaced the fuel bulb, hose, and flushed the tank adding fresh fuel/oil mix. When the motor is up to running temperature it becomes hard to start, and runs well for a few seconds then bogs down then revs back up. I believe it is probably a fuel issue rather than electrical. I've disconnected the fuel inlet hose from the carb to check the fuel pump operation, and checked the fuel tank vent hose. There don't seem to be any external fuel leaks, and was wondering if anyone here could suggest any more troubleshooting options, or problems that would cause this condition? Would be grateful for all suggestions, or comments.
Thanks, Mike.

I know you think the problem is fuel related and it may very well be, but have you looked at the coils? The coils on old OMC motors are amost always cracked and will cause problems, unless they have been replaced already. Also, you may get more replies if you put this in the JEGO's forum. JEGO = Johnson, Evinrude, Gale, OMC.

I agree, the most trouble I've ever had on an old V4 is due to a bad coil. Many times have seen a coil spark good when at home and the engine is cold. Out in the bay or lake running around, it'll either quit or you turn it off and it won't restart.

The coil is warming up and then it fails. When the engine is acting up, stop and check all cylinders for a strong spark.

Thanks for the info about the ignition coil, will try swapping it for another one, and see if things improve. I also moved my thread to the JEGO forum per your advice, I didn't know what the acronym stood for.

In my experience used coils are typically just as bad as the ones getting replaced.

Maybe it'll act up in a different way. Or if the problem doesn't change, it might lead you to the real problem.

Can't tell you how many used coils I put in the mag of a '62 75hp I had on a Glasspar G3. It never ran right until I put a new coil in it, then it purred. Started up like a car. Still devoured gas like crazy, but at least it ran well!

Well, after much grief I found out what the problem was! First, I swapped out the coil, using the one from my old motor as it worked ok before, per your suggestions. Started it up on the flushing attachment, and it was still acting up, would not idle well, and no amount of monkeying with the idle screws helped. Next I removed the carb, took the top off, and blew in the fuel inlet. Air was getting through, but just barely. Next I noticed when I held the top upright so the float would hang down the needle was not dropping with the float. Disassembled the float, and pulled the needle out to find a small sliver of rubber was wedged between the needle and the seat not allowing it to close completely, or open properly. Cleaned it up, and reassembled, and put the carb back on. Started it up again, and the engine immediately started behaving. Launched the next day, it runs like a scalded cat, and idles nicely. Kinda wish it had been the coil, would have saved me the trouble of pulling the carburetor which is a pita with all the hoses etc.

Thanks for providing the resolution!

Probably detritus from old fuel lines. Might be a good idea to replace if not done already, and to install an inline, cleanable, low-restriction fuel filter in the system to catch future debris.

Something like this K&N filter, cheap too:

www.amazon.com/81-0300-Replacement-Fuel-Filter/dp/B07X64ZN5H