'47 Martin 60 - Running poor at higher rpm

[sohcfour]

All -

I have a Martin 60 that is running poorly at higher speed. It will start fine and run around the "Start" position. However, as I increase speed and load it smokes, and will not rev very high. It sounds (and smells) like it is loading up in a rich condition. It also seem to run best as I lean out the mixture, but to a point where it eventually starves.

I have filed points, checked coils, confirmed I have spark. I soldered new spark plug wires a couple years ago. I have also cleaned and checked over the carb. Everything looks clean and sprayed through with cleaner and air.

The only thing I can think of (but am looking for other opinions) is the float height. I looked in a manual and it's not very clear how to check this. Does anyone have a practical means of doing this?

I'll quote the manual: "FLOAT LEVEL: Distance from top to float (at free end) opposite needle seat to lower edge of float chamber when needle is seated to be 1/8in +/-1/64in.

Thanks,

Matt

 

[GA_Boater]

Have you looked at compression?

 

[sohcfour]

Compression was about 95 cold on both.

 

[F_R]

Is carb throttle butterfly opening all the way and starting to open at the right time? Manual tells how to check the float level as well as anyone else can. Turn it upside down and measure it.

 

[sohcfour]

OK, I'm back from taking some old motors to the lake. The Martin didn't perform well. I'm inclined to think that it's a spark problem. It will start Ok in the "Start" position and it will run pretty good in the lower speed ranges. Once I throttle it up (and I confirmed the throttle mechanism is working properly), it runs strong on 1cyl and the other (lower) cylinder is running inconsistently. I'm assuming this is a spark problem at this point, because carburetion is good at low and mid speeds, and the top cylinder runs fine throughout the operating range.

The lower cylinder shows some spark (with a test light) but it is weaker. I'm guessing that higher cylinder pressures and lower cycle times are snuffing it out.

Any advice on testing the coils and condensers? I'm going to see if the points are available, I'm not sure. I did remove them and file them down, they looked terrible and I had to remove quite a bit to get them clean (prior to running the motor).

Thanks,

Matt

 

[F_R]

Martin parts source:
http://martinoutboards.com/

 

[sohcfour]

I'm about to contact them. What am I looking for? Points and condensers? Coils? At $40 they're not terrible but can I test them? Anyone know the correct resistance?

 

[F_R]

Don't guess--look. Just offhand, I don't know which coils the 60 has, Martin had a couple of different kinds. The old orange shellac coated ones are dang near bulletproof and very rarely go bad, but the black ones are notorious for cracking and NG. If you have the cracked black ones, no need to test, they are no good.

 

[sohcfour]

I have the orange shellac ones. They certainly look OK but I'm having trouble testing them. I can measure 1-2 Ohm across the primary circuits (the ground and condenser leads). But even trying multiple ranges on my multimeter, I can't get a measurement from the plug lead to either the condenser or ground on either coil.

 

[F_R]

That's highly unusual. But FYI, it should be a few k-Ohms on the secondary between plug lead and ground wire. "Few" like in around 5 k. Not sure of exact spec.