Here's the datasheet: http://www.arneh.dk/volvo/manuals/tamd31_hs45a.pdf
Looks like they put on the turbo to reduce emissions and increase power. If you removed the turbo the engine should work just fine. It doesn't say what the boost pressure from the turbo is but it probably isn't much. Your compression is 17.5:1 which isn't as bad as it could be. Will it start without using the glow plug?
Since your engine is heavier and bigger than other engines of the same power rating, even those without turbos, it may indicate superior quality. Longer piston rods reduce loads on the cylinders to make it last longer but make the engine bigger.
In any case, I think your engine is either too big or not geared/propped correctly. 2200 RPM is a little higher than you would want to prolong engine life. If this was a commercial fishing boat that would be a concern, but since you don't use the engine much it doesn't matter. You could get a smaller engine and run it at 2200 RPM. That would be more fuel efficient. Or you could get some kind of gear box with at 2:3 ratio or larger prop to run the engine at 1450 RPM so it would use less fuel and last 10,000 hours.
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I've had a hard time finding out real numbers about engine fuel consumption. They say gasoline is about 10 horsepower-hours per gallon. Two stroke is worse. The specs for a small < 10HP Chinese air cooled diesel is 183g/hp @ 2700 RPM. That's 17.7 horsepower-hours per gallon. They are direct injection and I think the compression is 20:1. The smaller ones are a little worse on efficiency than the bigger models.
A turbo increases the back pressure on the exhaust side and increases the pressure on the intake side. A typical pressure ratio is 1 intake to 1.5 exhaust. Higher is worse. Let's say it's 1:1 to make it simple. It has the opposite effect of running the engine on a high altitude mountain top. A partially loaded engine at sea level should still have about the same efficiency at high altitude shouldn't it, even though the full throttle power will be less? If you went below sea level that should hold true also, but full throttle would put out more power instead of less. That's what a turbo does.
I was thinking about it and a turbo can increase efficiency somewhat. If you increase an engine's power by 50% but the internal frictional losses are constant you do end up getting better economy out of it. But that only applies at high throttle. You can use a smaller engine in an automobile because of the turbo which saves on economy even more.
But for a boat would you choose a 16:1 compression engine with 50% boost from a turbo or would you pick 24:1 compression and no turbo? both engines are the same size and weight (not counting the turbo.) I would pick the 24:1. The 24:1 won't put out as much power as the 16:1 with turbo, but it will put out more power than a 16:1 while using the same amount of fuel.