With apologies to Lizzie Belle, I think she’s confusing Yanmars with certain models of Volvo
As you can see from the posts above, Yanmars, especially the 4JH’s, are widely beloved, so certainly no reason to reject a boat.
I have experience with Yanmars, Perkins/Westerbeke, and Volvos, and call tell you the following:
There are actually very few bad boat diesels made in the last 30 years. One particular model of Volvo gave a lot of trouble 20 years ago, which has hurt the reputation of Volvos, but most Volvos are absolutely fine. The engine is almost never the source of problems on board except in case of operator error or failure of the marinization parts, water
up the exhaust
, etc. So other than one particular model of Volvo, the make of the engine is just never a reason to reject a boat, assuming we’re talking about relatively modern boats with diesel engines.
Yanmars are the only boat diesels where both the engine and all the marinization systems are made in-house. So the engines are actually purpose built for marine
use, which might be some kind of a plus.
In my opinion, Yanmars, at least, 4 cylinder Yanmars, have the following pluses and minuses:
Very smooth running, quiet, sweet sounding
Very easy, reliable starting
Easy to work on (especially, because marinization parts are well integrated)
Widely available parts and service
Reputation for being smoky, although not all of them suffer from this
Parts expensive (but not as expensive as Volve)
Not as simple as Nanni, Beta
The 4JH’s are fast running engines, with redline near 4000 RPM
for some of them, which some people consider a disadvantage, but I don’t see any big problem with that.
injection systems – the most sensitive component of a diesel engine, by far – are top notch, made in Japan
by Zexel, known for better quality than the Bosch systems used on other diesels.
Parts are a double-edged sword. They are fairly expensive, but not as expensive as Volvo. Yanmar has a strict monopoly system which protects territories of parts dealers. This makes it impossible to find discounted parts. But they seem to require their dealers to carry significant stock (I guess tit for tat for getting a protected territory), so availability of parts is very good.
Yanmar dealers and workshops in almost every significant port worldwide.
Someone above suggested buying
the Yanmar impeller removal
tool – a hearty second to that. The seawater pump is mounted backwards on the 4JH without clearance between the pump and the starter to get a regular impeller puller in. It is extremely difficult, maybe impossible, to get the impeller out without the special tool. The clever tool is very effective and surprisingly cheap