Fuel Filter 1985 O'Day 28
I have the same boat, year and engine. Mine has 2 fuel filters. The cartridge filter is a Groco GE376, mounted starboard of the engine on the wall of the engine compartment and uses replaceable element GF376. With the key off (no fuel pump supply side pressure) remove the cartridge. I think there are a couple of bolts retaining the bottom of the assembly. You'll leak some diesel fuel so be ready to catch it if you can. It shouldn't be more than a few ounces as I recall. The spin on filter is toward the rear of the engine on the starboard side. I use a Kubota 70000-43081. This filter is taller than the original equipment filter and to use it I spaced the mounting bracket up away from the engine about 3/4' or so and used longer bolts as I recall. I did this because I couldn't get the original equipment filter regularly. Same deal on leakage. Before installing the new filter you can fill it with diesel fuel or after installing it empty, open the bleeder screw on the filter housing and turn the key on so the low pressure supply side fuel pump can purge the air. Good practice to purge the air with any filter replacement. You may want a helper so you can watch for fuel at the bleeder while a friend can turn the key off as you close the bleeder. I have never had a problem firing the engine up after this procedure. The universal engine book calls out a 298854 spin on. Hope this is of some help. I am not a professional so my comments are based only on my personal experiences. Does your boat have significant weather helm? If so have you had any luck diminishing it?
