I was wondering what type of ventilation you guys had to your engines? We're running a single 500hp and its been fine for the last 5 1/2 years but just interested to see what other people have in their setups.
Ocean Star is out of the water being repaired at the moment and we're carrying out our own upgrades at the same time. I've asked for a price and lead time on the spray rails from Lochin - they'll be a nice addition.
Part of the damage has resulted in a new galvanised keel band being fitted, along with new bow rails and A frame, Autohelm autopilot half fitted and I think an upgrade on the electronics might happen. Full repaint is also going on. We had 2x 1000 litre wing tanks for fuel up alongside the engine, but found too much weight up forward. We've removed them now and will be fitting a single, smaller tank aft of the engine - where the old one used to be!
I am on the lookout for a GPS radar / plotter combo colour if anyone knows of any being sold please get in touch.
the ventilation area (air inlet) to your engine is from high importance.
and it has to be BIG. especially if you have a 500Bhp unit. mine is also powered with a >500bhp and it takes here air
on 2 places. a big air vent that is build in in the engine cover, and one at the side of the air filter.
this one is a little annoying when going in high revs (turbo suction), but it is needed to have an good air flow to the air intake.
a quick calculation: +/- 9 ltr swept volume of the engine (for a 500bhp ) multiplied by its rotation (example 2000 rpm) speed is the NEEDED air for engine.= 9x 2000=18000ltr!!!!
so the engine rotating on 2000 rpm is consuming 18 cubic of fresh air !!!!;there is an % of additional air needed to have over pressure in the engine compartment.
this, to have a air supply that is in therms of speaking fresh(cold); in order for a good inter-cooling working principle.
i have to look in my note's to find the correct value for this %.
in my former job i was an engineer for bigger ship engines, >35000 bhp. there, i have seen the big importance of an good air supply.
it happened frequently that the oil was coming out of the auxillary engines dip sticks if ventilation was not sufficient. (vacuumized engine room due to air consumtion of the big ones)
plenty boaters do not know the importance of the air supply and engine configuration.
i recommend " never big enough" bigger vessel are using forced ventilation to engine room in over pressure!!! to avoid turbo problems
tomorrow i leave for work,i will see if i could find the correct formula for you and other intrested on this topic.
you will be surprised what the 500 bhp really needs for a good aspiration.
if doing some rebuild, consider to make your air intake's good big.
what type of engine, and cruise rev's do you use???
Monkfish has supplied you with enough information there I think! All I can add to that is mine has a downward facing scoop on the back of the wheelhouse the full width of the engine box and about 4 inch deep. According to the surveyor this has now to have a means of being closed off too should you have an engine fire. However, he also said that you can just shove the fire blanket in to stop the air! Mine worked fine with the Ford 280hp in
I'm just back from work, and the real value's for engine room ventilation (proffesional bigger boats working arround the globe artic included)
is as follow, minimum 18m³ for each Bhp in "one hour" of operation at rated load. in this amount of air supply, there is 4.5m³/Bhp/HR for the engine.
so thats very clear in what way you should supply air to your engine!!!  turbo efficiency,air surge, turbo-bearing wear and plenty others are badly influenced if
ventilation is not enough. it is imperrative to keep turbo suction force; to gain fresh air, as low as possible.
This is the reason that professional boats always make so much noise. its there forced ventilation
) multiplied by its rotation (example 2000 rpm) speed is the NEEDED air for engine.= 9x 2000=18000ltr!!!!
  turbo efficiency,air surge, turbo-bearing wear and plenty others are badly influenced if
