We are struggling to get our 50 Merc M47 running. It is the original flathead Merc engine...Compression is good, carb has been rebuilt and set, wire under distributor was fixed, new plugs, new plug wires, fuel pump, fuel, filter clean.... however, it starts perfect and sounds beautiful then after a few mins it starts coughing and backfiring or chugging and runs like crap. Frustrating and not sure where to look next. Any advice? Thanks
Sounds like a marginal coil; as soon as it starts to get hot, it starts failing. It could also be a bad condenser. The problem with condensers these days is many are of low quality and are bad right out of the box. You may need to try several before you set a good one.
Tubman's advice is a good place to start. If the coil and condenser don't pan out, I would start looking at a fuel supply issue. Look for something that is causing the fuel to get restricted, especially after it warms up. Hose could be collapsing or is pinched between the pump and tank, a loose fitting or bad tank pickup causing air ingestion, etc.
We are searching and digging into the suggested sources. I have another question, Where can I get or what replaces the vacuum advance VC263. Seems they are not available. We have decided to take the entire distributer out and clean, change any poor wires, connections etc to eliminate everything we can, gas lines and pick up seem ok, no air in fuel system being picked up, ordered a condenser and changing all the plugs while we are at it. All plug wires seem fine. Checked coil as well.
If your stock vacuum advance does not work, you have NO ignition advance, other than what you set initially. So, my advice is to replace the loadomatic distributor with an aftermarket mechanical advance distributor, point or electronic, and one with additional vacuum advance would be even better. This also allows a non-loadomatic carburetor change.
How did you "check the coil"? You can "ohm them out" and get good numbers(4-8 ohms on the primary and 8,000 ohms and up on the secondary) when it's cold, but it will break down when it heats up when it's in use. You should at least heat cycle it when testing. Also, with the quality of contemporary condensers, you should really get several while you're at it.
Hello, we did the ohm testing when cold and again when warmed up. We changed the condenser, actually managed to locate a vacuum advance and remove the fuel lines and though the tank was removed and cleaned a couple of years back there was some dirt in them and seemed to be causing a starving for fuel though the glass looked to have appropriate fuel in it. This afternoon we will be trying again with some alternative fuel line/source to see if we eliminate the issue. A huge thanks for the advice to all. I think we are on the right path....
make sure your gas tank...or gas cap is vented....easy check...just run with the cap off the tank good luck....you will get there
Another query. In changing the oil we are looking to replace with the same filter which is 8 inches long and 4 across. We searched the one that showing for the truck and it is way shorter. Does anyone know what we should be using?
Maybe check for a similar vintage Ford engine in a medium-duty chassis (school bus, grain truck, tractor, wrecker, etc.). They may have used a larger oil filter.
It is running!!! Thanks everyone, one more question, I need a 6 volt regulator positive ground. We have found them online for ford tractors. Would this be the same as the truck?
Essentially, not enough 6 Volt trucks running around anymore to market such products to. Quite a few more 6 Volt tractors still in service....
Probably. Or any of the well known flathead parts sellers will have the right one. Maybe even Rock Auto.
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