Re: mercury inline fuel line size
I replaced the lines between the carburetors with the 5/16th and even though it was thicker I was able to get it.I if replace the lines from the tank to the separator to the bulb and then the connector with 3/8th do you think I could leave the 5/16 lines forward of that -to the inline filter and the carburetors or am I setting myself up for a problem?
You may be looking at a problem. I'm not completely sure. Here's what mine did. I ran 3/8 all the way to the connector and then 5//16 becuase I couldn't make the 3/8 fit. When running early in the morning the engine would run fine at WOT for about the first ten minutes then, I think it was leaning out on the bottom cylinders. The symptom was bad pinging unless I shut the throttle down to no more than half. Pumping the bulb didn't seem to cure the problem either and it would persists throughout the day.
Of course my first suspicon was timing so, and I thought I found it when I found the wrong stator had been installed (according to CDI). Over time I replaced everything in the ignition system and still had the problem. So, I tore down the engine and went looking for something obscure. Eventually, I did find a sand hole in the block and had it fixed. But, you guessed it, the problem was still there!
Fianlly, I developed this theory, (and that's all it is). The lower carbs were slowly running out of fuel as the lines were not adequate to keep the bowls filled over time. At first I suspected the inline fuel filter/water separator but a direct connect didn't change things. Then I suspected the fuel pump but a full rebuild didn't change things. I finally figured out a way to make 3/8 fuel line fit using a 5/16 o.d. spring shoved into the 3/8 fuel line then heating and forming it to make the tight turns and eventually give the clearance need. I went through 5' of 3/8 fuel hose before I got it right.
The result seems to be that the problem is gone now. A lot of parts and money went into what turned out to be a cheap problem fix.
For the life of me I can't figure out you could positively trouble shoot this exact problem without a glass carb bowl or someones past experience.
So, theres your past experience, take it for what its worth. If you use 5/16 and this problem occurs, first figure out a way to make 3/8 work before you get overwhelmed with other ideas and head down the wrong path like I did.
