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Engine Compartment vents at stern #2405
08/07/07 08:25 PM
08/07/07 08:25 PM
Joined: May 2007
Posts: 1,234
Newport and Naples
Cap'n Vic Offline OP
Senior Member
Cap'n Vic  Offline OP
Senior Member
Joined: May 2007
Posts: 1,234
Newport and Naples
Long story ... several years ago I had to replace my diesel fuel line because it started to crack ... this was the second time ... but this time it only cracked in the engine compartment. Seemed to be really hot in the engine compartment.

I noticed another J30 had both vents facing forward ... then I looked at another J30 that had both facing the back. So I looked at the "dryer hose" that is used in the engine compartment and both of the hoses in my engine compartment ended up on the floor.

They originally used cable ties to hold the port vent tube at the top of the engine compartment to draw out the hot air. But 20+ years later those plastic cable ties are shot and break which dropped the vent tube to the floor.

It seems to me that the port vent is the hot air vent and should vent out toward the back.

The Starboard vent looks like it just goes into the space behind the engine panel ... then a dryer vent tube seems to run from the bottom of that compartment up to the top of the engine compartment and back down to the floor of the engine compartment.

It seems to me that this starboard tube is supposed to be the supply side of the ventilation. As such the starboard vent should face forward.

I did a quick run after I set it up as above and it seems that underway, I actually get warm air out of the port vent. Didn't work that way before.

Obviously when both tubes are at the bottom of the compartment there is no circulation.

Something for you guys to check out.

Vic #505

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Re: Engine Compartment vents at stern #2406
08/07/07 09:58 PM
08/07/07 09:58 PM
Joined: May 2007
Posts: 2,668
Portsmouth, RI
Rhapsody #348 Online content
Past J/30 Class President
Rhapsody #348  Online Content
Past J/30 Class President
Joined: May 2007
Posts: 2,668
Portsmouth, RI
Vic,

I'm worse off than you. The aft vents on Rhapsody are blanked off and I need to buy and install new vent cowls. I would route one of the "Dryer hoses" to the forward end of the engine compartment and the other near the aft end, then point the cowls in opposite directions to promote air flow.

Bill

Re: Engine Compartment vents at stern #2407
08/08/07 09:35 AM
08/08/07 09:35 AM
Joined: May 2007
Posts: 1,234
Newport and Naples
Cap'n Vic Offline OP
Senior Member
Cap'n Vic  Offline OP
Senior Member
Joined: May 2007
Posts: 1,234
Newport and Naples
funny thing is that i looked at the brochure ... hey I've had this boat since boat show 84 ... so I have the brochures and the pictures also show no cowls installed ... which is "supposed to be" racing "form". But when the hose only cracked in the engine compartment ... had to be something wrong. All I was trying to do is find out which way these vents go.

By the way the beat up original vents when painted with flat white rustoleum look great.

Access is no problem from the Starboard berth ... no wait you also have a port berth ... that would be better.

I have a spare J30 original brochure ... if you need it just send me your address and I will mail it off to you.

Vic #505

Re: Engine Compartment vents at stern #2408
08/27/07 10:07 PM
08/27/07 10:07 PM
Joined: Feb 2003
Posts: 127
Chicago, IL, US
rdpierce Offline
Senior Member
rdpierce  Offline
Senior Member
Joined: Feb 2003
Posts: 127
Chicago, IL, US
Uh oh....

My boat had two cowls in the back. One was connected to some kind of electric fan, the other disconnected. The blower never worked, so I removed it and all the hose materials. Now both cowls just vent into the space behind the engine panel.

Does the engine compartment need some kind of active ventilation? It's not like it's air tight, and the path of the hoses is still open.

Thanks,

Ryan Pierce
Tesara, #337


Ryan Pierce, #337
Re: Engine Compartment vents at stern #2409
08/28/07 07:53 AM
08/28/07 07:53 AM
Joined: May 2007
Posts: 2,668
Portsmouth, RI
Rhapsody #348 Online content
Past J/30 Class President
Rhapsody #348  Online Content
Past J/30 Class President
Joined: May 2007
Posts: 2,668
Portsmouth, RI
Ryan - I don't think the venting is critical for engine operation, because the space is not air tight, however...

The engine compartment should get some sort of ventilation to prolong engine life and remove the heat generated there. The engine intake consumes air in that space for engine combustion, and cooler air on the intake helps it run more efficiently. Also, if there are any fumes (e.g. exhaust leak, crankcase oil fumes, etc. you could create an unsafe condition below when motoring. Bottom line - the Yanmar won't stop operating if the space isn't vented, but it's safer to vent and in the long run, your Yanmar will feel better!

Re: Engine Compartment vents at stern #2410
08/28/07 08:35 AM
08/28/07 08:35 AM
Joined: May 2007
Posts: 1,234
Newport and Naples
Cap'n Vic Offline OP
Senior Member
Cap'n Vic  Offline OP
Senior Member
Joined: May 2007
Posts: 1,234
Newport and Naples
Just a reminder ... My first hint that there was a problem was when my rubber diesel fuel line started to crack ... ONLY in the motor compartment. And I didn't do a lot of motoring. So it had to be a heat problem. I don't remember my first J30 (a #300 something) that well, but the inside of the motor cover on #505 is covered with a sound insulation blanket ... probably insulates for heat as well. This problem probably doesn't matter short term ... but I've had #505 23 years so I sort of take a long term view. Like when I destroyed my first impeller on the water pump at the 15 year point. (power sailing on starboard tack heeled sucking air) They tried to sell me a spare ... "always need a spare impeller!"
I said no way ... this one only blew because i screwed up sucking air ... and I got 15 years out of it ...
I have it on my maintenance schedule to replace the impeller in 2015.

Vic #505


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