Originally Posted by Irish Rambler
If you use the BMW 3.0 litre 6 you can re-chip it to give more torque low down.
I take you point and it will probably work for a car, but boat engines need to be designed differently. The base engine needs to be a lot heavier castings with larger bearing to take the continuous loads, so many other differences that you see in off road equipment engines.
The modern can engine is being designed for light weight , small spaces, fast revving for a responsive and quick acceleration. But rarely run at WOT for more that a few seconds. These modern engines are amazing compared to the old engines of the 70'S and 80's ( electronic fuel injection helps greatly here). These are not the requirements of a trawler boat engine.
The modern diesel have come a long long way too, the fuel injection systems are night and day compared to the older systems but the engines still have to be designed for continuous high load use.
One example is oil pressure , if you have low oil pressure in a car you can baby it for ever and keep rolling , the worst that will happen is you have to call AAA If the engine goes , but in a boat if you low oil pressure at a high load it's all over very quickly.
A modern Car engine would be a very poor choice for a heavy boat engine.