jointventureII
Active member
Dear forum,
I've wondered for quite a while what the point of this tube (shown with the red arrows) is. Goes from the rocker cover, passes by the oil separators (?) and onto the turbo air filter.
And, 2nd question....can a dodgy wastegate reduce turbo output?
Reason I am asking is as follows. In November last year, I purchased a project boat, Bertram 25. This is quite heavy (3 tonnes or so) and has the above engine, a Cummins Mercruiser (VM) 4.2l 320hp diesel connected to a Bravo 2. On sea trials, we managed 21 knots but in very poor conditions with 4 on board and a less than clean bottom & leg. I removed the old turbo and had it tested, it was corroded heavily and, according to the turbo specialist, "not doing very much at all". Since replacing the turbo, riser and various other bits (almost everything except the wastegate), I've managed 24.5 knots on a clean hull, on my own having removed 80-100kg of stuff from the boat.
I was expecting quite a lot more to be honest, nearer 28, and I'm trying to figure out why before I go experimenting with propellers and different ratios in the sterndrive. Engine reaches max rpm (3900) with very little trouble so it could well be the prop.
I've wondered for quite a while what the point of this tube (shown with the red arrows) is. Goes from the rocker cover, passes by the oil separators (?) and onto the turbo air filter.
And, 2nd question....can a dodgy wastegate reduce turbo output?
Reason I am asking is as follows. In November last year, I purchased a project boat, Bertram 25. This is quite heavy (3 tonnes or so) and has the above engine, a Cummins Mercruiser (VM) 4.2l 320hp diesel connected to a Bravo 2. On sea trials, we managed 21 knots but in very poor conditions with 4 on board and a less than clean bottom & leg. I removed the old turbo and had it tested, it was corroded heavily and, according to the turbo specialist, "not doing very much at all". Since replacing the turbo, riser and various other bits (almost everything except the wastegate), I've managed 24.5 knots on a clean hull, on my own having removed 80-100kg of stuff from the boat.
I was expecting quite a lot more to be honest, nearer 28, and I'm trying to figure out why before I go experimenting with propellers and different ratios in the sterndrive. Engine reaches max rpm (3900) with very little trouble so it could well be the prop.
