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Marshall 22 engine vents
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6/18/2019 at 6:34:35 PM GMT
Posts: 17
Marshall 22 engine vents

Hey all Marshall 22 owners- I have a simple question hoping someone can advise me on.

When I bought my boat, the hoses from the cowl vents for the engine compartment/bilge on my boat were disconnected and piled up on the inside of the transom.

Finally got around to buying new hose. I have 2 vents, one forward facing one aft (like everyone else with a M22). I was just curious how the hose is routed in other Marshall 22 engine compartments.

I'm sure this is not critical by any means, I am simply curious.


6/18/2019 at 8:07:52 PM GMT
Posts: 68
Only have a M-18 with outboard, but have had other inboard engine boats. Best bet is to email Marshall. But in general, forward facing vent hose is air intake for combustion and compartmenr cooling, and should be up near the forward top of engine. Aft facing vent is for exhaust, cooling, and potential expelling of combustable/explosive fumes in bilge , and its hose should terminate low in the bilge (above high water, at least top of pump) and towards aft end of engine. If you have a gasoline engine, the exhaust must have a bilge blower, but most references seem to recommend it for all installations. May be intermittent or continuous operation (check carefully as it affects safety etc).
If gas engine, your should be running blower for 4-5 minutes before starting engine.

7/6/2019 at 4:09:39 PM GMT
Posts: 16

Hi Matt

I need to replace vent hoses myself.  I will look the next time I am down at my m22 Otter to see how they are run.


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7/8/2019 at 5:10:05 PM GMT
Posts: 17
Thanks! I called Geoff at Marshall Marine, he said it didn't really matter so long as they were not kinked and fed into the engine bay somewhere. Another benefit of a simple boat I suppose, but I'm still curious as to where yours go.

7/14/2019 at 2:27:54 PM GMT
Posts: 16
Hi Matt
no wind yesterday on the Chespeake Bay so I took advantage of the 90+ temps to work on the boat. I found that both of my tubes (dryer vent hose if you will) head down to the bilge area under the steering mechanism and are attached to nothing there. So yes it appears to be a way to get air to the engine from the deck reliably.

I put in a new set of deck vents (I am sure there is a nautical name for them) so disconnected the hose which is captured by an adapter ring that snugs on to the deck fitting. Picture will be posted next.

7/14/2019 at 2:30:43 PM GMT
Posts: 16
Hose on the water tank after removing from deck fitting, deck fitting from the locker looking like gods flashlight, top of deck fitting  and the vent hose headed in back of the boards on the port side that cover the water tank.  The hose terminates in the lower part of the bilge not attached to anything, just adding ventilation.

 Attached Images:

9/4/2019 at 8:42:41 PM GMT
Posts: 5
On my 22 I currently only have one vent hose hooked up. It's attach to the Cowl vent which is facing forward. The other Cowl vent is facing aft and the hose has been removed. The idea is air is forced in thru the forward facing Cowl vent down the hose to low in the bilge. The heat from the engine rises and exits from the Cowl vent with no hose. I've been running like this for the past few years without issue.

Last edited Wednesday, September 4, 2019
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