Boat Engines-Reliability and Efficiency
Most sailing boats will have an installed diesel engine and that engine is a safety essential. Of course motorboats (with no sailing ability) rely 100% on their engines, so the whole installation must be beyond reproach. Planing and semi-planing hulls use phenomenal amounts of diesel and tip top engine tune and efficiency are essential.
Compared to current day cars and trucks, diesel engines in boats are a bit agricultural. Installing a modern car type diesel with electronic injection control, EGR valve, DPF exhaust, et cetera is probably not a sensible option, as the electronics are nothing but a liability on a boat. Tried and tested mechanical fuel pumps and injectors mean that a proper marine diesel will keep running happily in the absence of electricity... and even be hand started if it has a heavy flywheel. Simplicity is the key to reliability afloat.
Simple, reliable but old fashioned
The downside of this is that boat engines don't run as cleanly as modern diesels in cars, and are not as economical.
Also all diesels run most efficiently and cleanly at around 75% of max continious revs. Often in yachts, they are running very lightly at lower revs when motorsailing, marina handling, etc. This leads to carbon deposits caused by inefficient fuel burning.. and of course pollution.
The marine fuel tank installation is highly susceptible to condensation (as is the shoreside marine diesel supply), and thus introducing water into the diesel fuel. Problem is certain bacteria thrive on the interface of water and diesel as the water settles into a layer at the bottom of the tank. Diesel Bug. This bacterial contamination can build up into a black sludge which can find its way into piping and filters and cause blockages. Normally just when you don't want… When the sea is kicking up rough and the fuel in the tanks is getting very disturbed.
To make matters worse, bio diesel is now being added to marine diesel (to make it greener..), up to 7%. Biodiesel is hygroscopic; meaning it attracts water, simply adding to the problem above.
So we have three separate issues here:
1. Old-style engines ofter past their best, not being so fuel efficient, and giving off more pollution than they should.
2. Inefficient running caused by low revs cokes up the engine parts, and leads to maintenance issues and lower efficiency.. ie engine burns more fuel and makes more pollution.
2. Diesel bug sludge in the fuel tanks can cause serious reliability issues unless kept on top of by rigourous housekeeping. (Topping up fuel tank to full before the winter layup will prevent condensation on the tank walls, plus draining and changing fuel filters at the start of the season should be considered the minimum fuel system maintenance.)
Please continue with this series of articles to find the ZERO cost solution to the problems above.
Footnote:
Marine diesel installations I have lived with:
1. A marinised BMC taxi engine, about 40 hp in a 36' yacht. Awful, noisy and terrible vibrations. Didn't keep this for long.
2. A Gardner 8L3 (152 HP) installation in a 66' MFV conversion. Beautiful. Ultra reliable, quiet. Two 24v starter motors and decompressors on all 8 cylinders... easy starting even with low batteries in freezing cold. Two ancient wing tanks, each 200+ gallons, hot swappable filter system with electric and manual pumps feeding 40 gal gravity flowing header tank. Even with all the pre-filtering, in very rough weather, the final micro-mesh filter on the engine itself blocked a couple of times over many years. This meant heaving to under mizzen sail, and cleaning that filter. 15 min job. The engine could make a lot of smoke and sparks when put to very hard work after light use. (Running hard for the last hour after continious light use was recommended to me by a ships engineer.. to clear out the gunk). Fuel consumption 2 to 2.5 gallons /hr at 7 knts cruising speed, engine running at about 60 HP, at 520 RPM ! Had this boat about 10 years and covered over 25,000 miles.
3. A Volvo MD2B twin cylinder 25 HP, in a 31' yacht. This ancient old thumper was a proper marine diesel. Hand start-able, decompressors, etc. Very reliable but quite smoky probably on it's last legs. Had this boat about 9 years and covered over 15,000 miles. Never had a diesel bug problem stop it. Would use about one third of a gallon per hour at 5 knts.
Certainly the last 2 above would have benefitted from the treatment that's going to be described.