I'm also preparing a M51 to go into my Bayliner 20,5 ft cuddy cruiser.
It used to be powered by a Mercruiser 4.3 V6, but with the fuelprices over here (Netherlands) and because I was looking for a challenge, I went for a repower
I'm going to use a Bowman water/water exchanger and for charge air an aftermarket aluminium water-to-air exchanger which is being anodisised as we speak for better (sea)water resistance.
I will be using the standard Alpha One gen 2 that came with the boat. I was thinking about a speed-up box directly behind the engine to speed up the rpm's before it enters the sterndrive. That way the torque on the drive will be less. Also pitch
of the prop can be a bit less then, also better for the drive (less stress)
No sure if it will be able to shift with higher idle rpm's though.
For the engine I will be using an exhaust
manifold out of a 524td, because of the higher position of the turbo. That way the riser will be much shorter before it will be wetted. The manifold and the turbo will be isolated, but not wetted.
Just wondering now if I should modify the oil
sump. The actual sump is in the front of the engine, while most of the time, (slow cruising speeds in rivers) the engine will be leaning a bit backwards. Also with accelaration it will be harder for the oil to get back to the front of the engine.
What do you guys think of this project?