On survey, it was noted that my boat's engine room blowers sucked air IN
rather than blowing it OUT, and it was recommended they be reversed.
However, nave as I then was - and probably still am - I figured the
builder knew what he was doing, and left them as they were. (I admit to
also being a tad lazy.)

Based on this thread, I suspect the builder was right about the fan
direction, and that the twin 120 Lehmans need more cool, fresh air than
the wimpy vents can provide on their own. Even were the vents bigger, I
suspect a trawler running at maximum speed isn't going to deliver the
kind of volume and rate that Glenn Wauss suggests is needed.

Opinions on fan-driven engine room air supply?

Cheers, Garrett

IMHO, there is nothing a diesel engine likes more than cold, dense air for
best performance.  I have twin Lehman's as well and had the same wimpy
little vents with a single fan sucking air out of the engine room.

Not any longer, I put a 90 cfm fan at the back and jam as much cool air as I
can into the room while running.  I definitely reduced the temp in the room
and so far, neither of my babies have complained about the draft.

On the other hand, I did have an ex commercial fisherman suggest that if I
ever had an oil line break (with resulting spray of oil on hot metal) I'd
want to be able to vent the room.  So I do plan to add another fan going the
other direction - for emergencies only.  That is if my original plan of
hinging the existing fan (to reverse direction) doesn't work out.

An old time merchant marine chief engineer told me to forget about sucking
the air out of the room in the event of a fire.  Said you'd just suck the
fire into some other part of the boat.  He advised that in the event of fire
it was best to shut down all ventilation in either direction.

Yesterday I was out for a short cruise on a friends
Roughwater and we topped up the fuel tanks. He had a
great gizmo that caught any fuel over flow if you
filled to full. Its at west marine for 18.99 or close.
Its in the catalog. I cant recall exactly but I want
to say page 18. and I think it ws called spill saver.

It is a plastic cup with two suction cups on the
sides. You wet the suction cups and place the cup over
the fuel vent. It acts as a container for fuel that
gurgles out of the vent. pretty easy to use and real
handy. One of my next purchases or maybe might make
one myself.

Dan
37 Roughwater
"Wen I Dream"

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SNIP<<< It is a plastic cup with two suction cups on the
sides. You wet the suction cups and place the cup over
the fuel vent. >>>ENDSNIP

When we filled up in Poulsbo this summer the dock guy asked if I minded
if he attached one of these to our fuel vent.  As Joe says, its easier
on the side against the fuel dock.

Gregg mcKay
Tolly 37