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Rainshadow, hull #126, doesn’t have any air vents into the engine room. I’ve read that other Nic 38s have a louvered vent below the helm, but this area is solid on Rainshadow. Perhaps the later model boats had that area removed after there started to be worries about boarding waves and the low cockpit floor?
Anyway, it appears the only air access for the engine is via the bilge. While there are a lot of ‘holes’ throughout the boat into the bilge, there still seems to be insufficient air reaching the engine because when we try to lift off the small engine access hatch at the forward end of the cockpit floor, there seems to be a vacuum pulling it back down.
We are still running the original Perkins 4-108, and its going strong, so maybe 35 years of no air vent has done no harm, but it seems wrong.
Has anyone added engine room vents to their boat?
Ronar M has the vent you mentioned beneath the wheel though I had to change it for one I could close when I went commercial and had to get a licence. The other thing that occurs to me is that you should look at the engine air intake. It’s that mushroom shaped thing on the right hand side of the engine. Ronar’s was completely blocked with oily fluff. How the engine continued to run, goodness only knows. Thank providence for good old Perkins engineering.
Trevor
Yes, we checked the engine air intake too – the mushroom shaped thing. It was pretty dirty, but not scary dirty.
Under this mushroom cap there is a tube that leads from the engine to the center of the mushroom, that is, it bypasses the filter. We were surprised to find a breather hole in that tube. This tube must have something to do with the engine air usage, and the hole something of a venturi effect. We asked our mechanic about it, and he didn’t have much insight into why the tube would have a big hole that is open to the engine room without any intervening filters, which seems like it could suck unfiltered air directly into the engine. But as you say, the trusty Perkins is still running strong, so…
MarilynRe: the “hole on the mushroom thing” (air filter)… on the Perkins 4107 (mine still runs great,too) there is (or should be) a short hose just under the “cap” of the “mushroom” going from there to the valve cover. This is for crankcase ventilation and has nothing to do with getting air to the engine for combustion of the diesel fuel. If this hose is missing it’s no big deal as the crankcase will still get the required ventilation.
Fred “Oasis” #99
Gosling (Nic 42) has vents that were fed by an engine room exhaust fan but that was disconnected years ago. We always run with the lazarettes hatches open on one side at least. We have direct access to the engine from both lazarettes in the cockpit in the 42. Unless you have a real reason to vent such as an exhaust leak there should be no real requirement to improve circulation any more than that.
Cheers, J-G
Gosling C&N 42/6Jeremy Lines wrote me an email saying he’s rather surprised we have no engine vent because he thought all boats had one installed at CN. He asked if something else could have been installed in its place by PO. Good question.
Below is a photo of our area under the helm. You can see below the foot rest, we installed a high water alarm (salvaged from home alarm, so a little unsightly, but generally hidden). Above the foot rest, there is the controls for the Nico autopilot, which I thought was original equipment. There is no area that looks like its been filled.
Can anyone tell me where your engine vent is located under the helm?
Jeremy just wrote me another email, and said this:
“That is the answer!!! We never fitted a Neco there, that is where the vent was!. You really must have good ventilation to the engine space. You really should have an extractor fan which then requires a bigger inlet.”Of course, that Nico control has been there a very long time. Maybe not 36 years, but a most of that time certainly. Now we just need to decide, after all these years, whether it really does make any difference to the engine efficiency, or longivity, to not have a dedicated louvre to allow the engine to breath.
Running with the lazerette open is not an option, because our lockers are mostly isolated from the engine room. We could temporarily run with, for example, the floor board over the bilge in the aft cabin open to see how much difference it makes. Of course, we’ve tried that for a few minutes, and the increase in noise overwhelms any other senses, so we put the cover back down again quite quickly. Scary to watch the prop shaft spinning anyway.
I just found some interesting posts on the Cruiser forum on topics covered in this post:
– Conversation about the breather pipe on the Perkins 4-108, see here
– Conversation about the need to ventilate the engine room to better dissapate heat that may affect sensitive electrical components, such as the alternator, see here
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