Affectionately known as a Cement Mixer Engine because of it's simple and rugged design, The Volvo MD2B was the successor to the MD2 and the predecessor to the MD2C. Volvo stopped making the MD2B in 1975.
Two cylinders, raw water cooled, with the Volvo hand crank and compression release levers and a 200 lb. flywheel, the engine seems to be one that can run for a very long time.
My particular installation uses fabricated steel engine mounts that bolt to four of the keel bolts. The standard belt driven starter / generator is supplemented with an alternator to boost the meager 10 amps that the generator outputs by another 30 amps. I like this approach because the generator is usually switched to charge the starting battery and the alternator is switched to the House battery. That way each gets it's own regulation charge and I don't have to leave the battery switches in the 'BOTH' position or have a battery combiner. I installed a 'smart' voltage regulator by Ample Power to the alternator when the stock Volvo regulator burned out in '96. The replacement regulator from Volvo was about $140 and the smart regulator was less than that on sale. The Marchand alternator does get pretty hot when fully charging a weak battery, but then it shuts down and cools off when the battery is charged. Since I'm only chargine one group 27 battery, it charges pretty quickly. A high output (70A) alternator will address the heating someday. I guess I could limit the alternator field current with a resistor also.
The problems with this engine are 1) the noise and 2) the cost of replacement parts. The noise is mostly due to the hard steel engine mounts. There is no vibration dampening between the engine, keel, hull and mast. Since the engine has not been built since 1975, each part is apparently a valuable antique and is charged as such by Volvo.
Oil Pressure Problem
When I changed the oil or removed the dipstick tube, I found that the oil pressure would not happen. Very disturbing. It happens that the tube and it's gasket are critical to the oil pressure since the oil pump is well above the oil sump level, and perfect suction must be maintained in order for the pump to prime. After it primed the pressure was OK, but then after the engine ran for a long time (thin hot oil) the pressure would drop to about 20 PSI.
In early '97, I rebuilt the oil pump to make it prime better and run with higher pressure. The pump is located behind the flywheel on the front of the engine. It is easy to remove without removing the flywheel, and required only light honing of the flat surfaces with emery cloth on a flat surface, and replacement of the gaskets. The only special tool required was very thin 0.003 feeler gauges to check clearances. You add enough gaskets to make the clearances right. The operation was a complete success. After two subsequent oil changes it primed right away, and ran with higher oil pressure when hot.After two seasons the oil pressure has held up well.
'98 Cooling System
When replacing the thermostat, I found significant crud, rust and sediment in the exhaust manifold. In 1998, I experienced occasional mild overheating. I was also concerned that the exhaust manifold had not been replaced in many years. Maybe not since 1975. A failure here would cause engine damage. I decided to replace the manifold, and give the cooling passages a good cleaning out, and add a raw water strainer to the system. And rebuild the water pump which leaks a bit.
The manifold and gaskets were purchased in the late fall. Good thing since the manifold took a month or so to arrive and I didn't need it 'till spring. I got a bronze Groco strainer, and the local Volvo shop (Yankee Engine in Danvers, MA) had the water pump seals, screws, pump impeller, thermostat, etc.
The old manifold came right off. The new manifold went right on.The only challenge was that the temp sender would not fit the new manifold. After arguing with Volvo tech support about why they changed the hole size, I realized that the old one had an adapter and a non-standard sender in it. I souldn't find a pipe adapter that fit right so I bought the standard Volvo sender and it fit fine, of course. But I had to now replace the gauge with a VDO guage: $130 from Volvo. After a bit of net surfing,I found a VDO dealer: Palo Alto Speedometer and ordered a gague for $50.
When attempting to replace a cylinder engine drain cock, I realized that the engine hole threads, allegedly 1/8" pipe thread, had loosened up (or corroded or something) so that the standard Volvo cocks just rotated in the hole. Not good. I bought some brass pipe adapters and they fit OK. I ended up using the new brass pipe fittings as adapters to the Volvo cocks. It's a bit of a hack but it works fine.
When I pulled the cocks, there was considerable crud in the holes. The crud accumulates around the cylinders and only some of it comes out with annual flushing. I started this flush job by warming up the engine and sucking in a gallon of "Marsolve". Marsolve (www.marsolve.com) is supposed to dissolve sediment and salt without dissolving the engine. Left it in for an hour. Practical Sailor spoke highly of it in the Feb 15 '99 issue. I realized that the way the cooling passages work is that if one of the two cylinders is blocked or partially blocked, the cooling water simply diverts to the other one. So I set about flushing each cylinder individually. By applying city water to the manifold intake and closing one cylinder at a time, I was able to force water into each opening one at a time. 1/8" pipe nipples and removing the starter allowed each cylinder to be flushed from both directions. I think I got most of it that way.
The water pump rebuild is trivial and cheap. I put up with a drippy pump for how many years? The raw water strainer installation was also a piece of cake. Now sand and eelgrass witll stay out of the engine. The system works swell. No overheating at all and the engine runs at a nice steady 170F.
Generally regarding my MD2B, I really baby it with operation at low RPM's (many other boats pass us), the best oil, and any preventative maintenance I can think of. Keep the cooling passages cleaned out with a good flush each year. I replace the thermostat every 2-3 years.
One thing I've done to extend the life is to use only synthetic ($5 a quart) Volvo diesel oil. It is supposed to lubricate better. It too is available from Volvo dealers. I figured $25 a year for insurance is cheap.
Part of my sucess with the MD2B has been that my boatyard, Yankee Engine in Danvers MA is a Volvo penta dealer. When I need a gasket, filter, or screw, I generally have it in 5 minutes. Other than an authorized Volvo dealer, I don't know where to get parts. I do know you can get some parts like oil filters and water pump impellers at BoatUS. Volvo car oil filters (240, 740) fit OK too.
Last year (1999) the starter went. I thought it was just the brushes, but new brushes didn't do it. It went slowly: If I released the pressure relief lever I could get it to turn over and start. Fortunately I had a spare starter and was able to swap it in later in the season. I still haven't had the original rebuilt so I can't say what's wrong or how much to fix.
When cold, I always need to press the cold start button. It will not start otherwise. After it was warmed up, the button wasn't necessary.
The end of this story is
that I'm planning to replace it with a modern engine in a year or so. The
noise, hard engine mounts (vibration) , salt water cooling, less reliability
and hard to get parts, 25 years of age, plus a planed trip to the
Carribean in a couple of years have convinved me that $6,500 plus installation
isn't too much for a new Yanmar or Westerbeke. I'll still be going one
or two more seasons with the MD2B though.
Questions about the MD2B:
Any corrosion problems with the MD2B being a salt water cooled engine? I have not heard of any and am careful to maintain the Zinc on my prop shaft and keep an eye on the longevity of the exhaust manifold.
My engine will generally
not cold start without pushing the priming button. Is this a problem? One
that can be fixed?