Heavy Carbon Sooting On Transom

A racor filter typically uses the bottom 1/2 or so of the filter at first and as it becomes clogged, the fuel level in the racor works it's way up to the clean top half of the filter. As it becomes clogged, the micron size does become smaller. How many hours is a 30 micron filter lasting? Generally in most cases the fuel you're buying is relatively clean and the contaminents on most yachts are in the tanks and the algae is growing in the tanks, the 10 micron will filter it better, but of course would become clogged sooner.

If your 30 microns are immediately becoming clogged with debris, then I wouldn't switch to a smaller micron. With relatively clean fuel, only debris 30 microns or larger should get caught in the filter, anything smaller then passes through, so it could take a while before the racor actually starts filtering at a smaller micron amount, meanwhile you're secondaries could be clogged. On this particular Hatteras I ran, the 30 micron dahls would be relatively clean, and the secondaries would be packed causing a bad black smoking condition. Unfortunately dahl only makes 2 micron and 30 micron filters and we felt the 2 microns would clog too quickly and just continued to change secondaries. If Dahl had made 10 microns, we would've switched to them. As cheap as racors are, and as easy as they are to change, I'd try 10's and have spares on board (racors are a lot cheaper than your volvo secondaries). And, you almost always get an airlock condition when changing volvo secondaries and have to keep bleeding out of the bleed screw. I've also had a set of Volvo's that started black smoking really badly and it was the air filters.

If you've got 150 hours on your 30 micron racors, I'd go ahead and switch to 10 micron racors as your fuel seems clean enough to not have an issue going to the 10 microns. What size Racor elements are on your boat, single or dual?

I use only the #920 on the transom. After a good cleaning with it the transom looks like it's waxed. I tried awlcare, wax, polymers of various types and they all hold soot and dirt. Polymers seem to hold the most dirt/soot in my experience.

Yes, but if I remember correctly your boat has Awlgrip paint, which should never be waxed, nor does Awlgrip need wax for longevity.

Gelcoat OTO should be waxed for longevity purposes, even if it does indeed hold soot. You could always wash the transom with rolloff, then just wax it each time with a cleaner wax. It doesn't take but 30 mins to wax most transoms on a yacht 60' and below.

Well as usual, YMMV, because that is the apposite of my experiance with Zaino. I've always found wax to hold the most soot and black rain streaks.

Where as with Zaino I see less of both and both are far easier to remove.

Intercooler

I had a similar problem on a 140 PJ. We went nuts trying to get the black transom to go away... new filters, new injectors, back pressure tests. Turned out that the inter-cooler was fouled by blow-by from the breather. The boat did not have a breather separator filter. It made me a real believer is breather separators.

Oceaneer

I would put a 10 micron in 1 side and a 30 micron in the other side. Run on only the 10 micron side and with clean secondaries check vaccuum at cruise speed underway to get a baseline. Then monitor them everytime you're at cruise. Then if you do have an issue you can switch over to the 30 micron. I think you'd be fine running a 10 micron racor and save your secondaries from a little buildup. Also most people change their fuel filters at 100 hours over here......but if they look fairly clean they leave them.