I replaced a Sole with a Sole after considering the Yanmar option. It's a good
motor and the new models are easy enough to source
parts for (the engines are used by Caterpillar and Mahindra in various forms). The Mitsubishi engine is solid, low revving and is very old
school which to my mind = simple to maintain and
repair. The Yanmar is probably better for resale, so this would possibly cancel out the
purchase price difference.
However, for a
DIY install, a Yanmar is problematic if replacing a non-Yanmar engine. Firstly, they use their own gearbox flange which has dimensions different from everyone else's so the shaft coupler will also need replacing (which can be an exercise in itself and can require shaft
removal for machining the face) and, secondly (iirc), The mounts are lower and closer to the shaft centreline than most other engines - certainly the Sole - which could result in some major engine
bed modifications. There's also the fact that Yanmar
DIY installs are frowned upon to the point you'll need to include an extra
boat buck or two for
installation and the spare part prices enjoy a Volvo-esque reputation.
Perhaps the Betamarine range of engines would be more suitable for your case. The Kubota
motor used is bullet proof and they can maybe provide a unit to the same mounting specifications as the original Sole as an option and this would allow it to drop right in. The only thing they can't do is provide the same connection locations so you need to check that the location of the gearbox lever,
exhaust,
fuel lines and general protrusions will
work with your engine bay.