The MD30 is a four cylinder marine diesel.* It also came in a variety of version including the TMD30, TAMD30 and the AQAD30.* Volvo use to code their engine with M being marine, D diesel, T turbo, A aftercooled and AQ indicating an inboard/outboard drive.
I have a 1981 vintage TMD40A, which is a six cylinder, 117 hp inboard, turbocharged engine with a Borg Warner Velvet Drive transmission.* I have over 4200 hours on this engine and have had virtually no problems.* The only thing I have replaced in the six years I have owned the boat are the glow plugs and a broken on-engine raw water strainer.* The glow plugs were like $40 each and did have to be ordered by my supplier (North Harbor Diesel in Anacortes, WA).* The on engine strainer is really superfluous to the needs of the engine since my boat had a Perko raw water strainer between the through hull and the engine.* I removed the plastic strainer basket and assembly and plumbed in hoses to go from the shaft driven raw water pump to the heat exchangers.* Oh yeah, I bought a new raw water pump because the old one was leaking at the aft end of the housing.* The new one is still on the boat as a spare because the old one simply needed a rebuild kit that comes with the $65 impellor.* Installing the new seals and the new impellor solved the leak.
I religiously change engine oil at 100 hours, filter and oil again at 200 hours and transmission fluid at 200 hours.* I also do an annual oil sample of both the engine and the transmission.* In six years my oil samples have been consistent and have had no out of tolerance particulates.
Volvo Pentas are very popular among commercial fisherman.* I would not rule out any boat just because it has a Volvo engine.* If you get serious about the boat than have a local engine maintainer do a thorough survey of the engine, do oil samples, compression checks and maybe even injector tests.* Don't rule out a boat because someone said that the parts are expensive...what you are looking for is a well maintained and healthy engine.* As pointed out by Marin, Volvos can run for a long, long time.* As with airplanes, boats and diesel engines are designed to be run and they work better if you run them right, maintain them right and don't abuse them.
Step Williford
Oak Harbor, WA
1981 Great Lakes Trawler