Water in engine air ducts, A25

[WillieC]

Combustion and cooling air for the engine and compartment comes from the two rectangular ducts that open to the engine compartment and originate at the two huge toe stubbers/ankle busters on the rear deck. We have all learned to not drill into them at the transom when mounting swim platforms or transducers or aux engine mounts, etc.

The forward ends daylight in the engine compartment at the two holes cut into back ends of the engine bed stringers. At the rear of the engine, one can slip a rag between the two holes under and behind the engine drip pan.

Mine occasionally collect water in them, visible where they open to the engine compartment. I have suspected leaky vents at the rear deck, and have been watching them during our recent ill weather. Not conclusive yet that this is the source. Where else could water be coming from? I should have spent more time nailing this down when I had the engine out, but it was sunny and warm and so what? I originally thought these ducts would drain to the bilge, which is why I dumped raw water from the HX circuit into them, and found out mine do not drain into the bilge. (Boat is on the trailer at this time. Maybe angle of dangle is critical, of the boat, that is.)

Water showing up where it is usually dry is disconcerting so I am busy chasing down all the annoying little leaks that work the dehydrators overtime all winter. I may pour the ducts full and see where (or if) it leaks out as part of my investigation. I want to be certain it is not coming from below the waterline, through the hull?! Since it is on the trailer, I will be very happy if they collect water this winter so I can rule out through hull intrusion. I should have tasted it, but everything on the boat tastes like salt. It was not oily, only slightly cloudy.

It is amazing how little a leak will collect so much water and how far it will travel. I have a teeny, tiny leak at the starboard v-birth window rubber which trails down the fiberglass into the little clothes closet and then back toward the head where it hits the plywood wall and tracks down until it hits the floor pan in the head and then pools under the Jabsco making it look like I don't even try to hit the receptacle, which I usually don't much preferring the wide open spaces of the swim platform. The things I get blamed for!

Any insight is always appreciated. Especially from those of you who have replaced your engines and did what I should have.

[kerrye]

I can't answer your question, however, the lack of a drain in the engine compartment means I'm not surprised that those vents don't drain either. I drilled a hole in my engine compartment so it drains into the forward bilge. Maybe it's possible to drill a couple of small holes in those vent channels so they drain into the engine compartment and from there into the bilge if you have the engine compartment drilled.

Isn't the deck angled in such a way that water runs towards the stern? I think mine is. That would mean the seal at those vent cowls would be challenged constantly in any rain or spray by any water which didn't run out of the scuppers on the deck.

[WillieC]

I consider all my deck fittings challenged in our climate. I have no doubt that I need to rebed the cowlings as everything else I have touched on the deck needs rebedding. I am just trying to isolate where the water in the ducts is coming from. Then I can decide how much I should worry about it.

The 'scuppers' on the deck on WillieC consist of a 1/2" hole. Nicely beveled at the deck, though. It only takes about three Doug fir needles to clog them. I sure would like to unclutter that back deck by moving those intake cowlings somewhere else. There's another topic for discussion.

Thanks, Kerry.

[dkirsop]

I haven't noticed water in my air intake channels but unlike yours mine open towards the front of the engine bed under the engine. The only time I was able to get a good look into them was when I had the engine out. Nothing was found at that time and the boat had stood outside but under cover all winter. I wouldn't worry too much about the occasional moisture getting in, if that's what it is, as the air flow to engine would be more than adequate to dry them out. I'd start with the bedding of the air intakes. I should mention that for winter I cover the boat with a simple tarp structure that is well vented and sheds water. I haven't done this yet this fall because I am waiting to have a tree removed near to where I store my boat but I might post a blog on how I go about this once I have next years load of fire wood sorted.

[WillieC]

"unlike yours mine open towards the front of the engine bed under the engine. "

Dave, mine do the same. At some point, though, they become solid as this is what the engine bolts to. I apologize for mis-stating this. Maybe the solid part is directly under the engine mounts only. It appears that there is some kind of steel insert as my engine mounts bolt into tapped holes in the beds. Was a piece of channel or angle iron glassed in, maybe a piece of flat stock? Who knows. I have seen how some engine swaps incorporate chunks of angle iron bolted onto the old fiberglassed beds thus allowing for new engine mount locations. Anyway, my air channels extend forward like yours.
Again, I am not worried about the presence of a little water, I just want to make sure I am not missing something big. I also am trying to maintain my hull speed advantage over Desert Albin for our Cannonball run to Desolation Sound next summer. At 6 knots.