Click for JetForums Click for Nordhavn Click for Abeking Click for Lurssen Click for Westport

Engine room air intake

Discussion in 'Ocean Yacht' started by Mike Gerus, Jun 3, 2020.

You need to be registered and signed in to view this content.
  1. Mike Gerus

    Mike Gerus New Member

    Joined:
    Jun 1, 2020
    Messages:
    2
    Location:
    Mexico
    a 1984 ocean 55 sport fish. While doing some wood repair I noticed that you could look right out the port air intake vent. Pulled the inspection cover on starboard and had a fiberglass shrowed which I believe is meant to keep the water out. Any one know what is required ? Really do not want to tear apart boat just for a education.
    Mike
  2. praetorian47

    praetorian47 Senior Member

    Joined:
    Aug 22, 2011
    Messages:
    258
    Location:
    Bayport, Midland, Ontario
    Do you have pictures? Mine is an 88, but I doubt they changed that much and I find the air flow pretty restricted. I'd love to know if we can easily increase it.
  3. NYCAP123

    NYCAP123 Senior Member

    Joined:
    Mar 14, 2008
    Messages:
    11,218
    Location:
    Long Island, NY
    What's required is that boat buyers have an educated eye, and please do tear apart your boat for education. You want to be familiar with every inch of it. Better to do that at the dock than when you're broken down on the water (or worse, taking on water). As far as air intakes are concerned does your vent encourage air to be pushed in, but water to be blocked out and drained overboard.
  4. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    13,933
    Location:
    Fort Lauderdale
    Nothing is required as far as having an opening there. Usually they have a lip and a drain to keep water out and only let air in. Some have screens, most from your era do not. The engine vent is required to allow enough air in so that the motors get enough airflow at WOT.
  5. cleanslate

    cleanslate Senior Member

    Joined:
    May 29, 2018
    Messages:
    1,228
    Location:
    Cherry Hill, NJ
    Don’t mess with it and keep on with the woodwork it’s been doing a fine job for 35 years let it be.
    If one side has some sort of factory installed plastic shroud and the other doesn’t try to make up your own the best you can and duplicate it but don’t worry about it too much in my opinion.
  6. Capt Fred

    Capt Fred Senior Member

    Joined:
    Jun 22, 2009
    Messages:
    297
    Location:
    Long Beach CA
    My 44 has a glass shroud on both pt and stbd. Ducts come off the top to prevent water from having direct access to the ER. You can continue to run her in calm conditions but IMO I would get it fixed to keep as much salt out of the ER as possible.
  7. rtrafford

    rtrafford Senior Member

    Joined:
    Jul 13, 2019
    Messages:
    989
    Location:
    Vero Beach

    Yes. While you're in there, check and look for salt residue in the ER around the vicinity of these vents. If they're doing their job right you won't have any/much. IF the vents are different int he capacity described, good chance you'll see a difference between the two if you're running in salt conditions. Given the inflow of air and propensity for spray in this location of the hull, you don't want that salt finding its way into the ER...
  8. Mike Gerus

    Mike Gerus New Member

    Joined:
    Jun 1, 2020
    Messages:
    2
    Location:
    Mexico
    I have had this boat for 10 years and have always had intake and filter collapse problems? I have had to repair and clean the turbos yearly along with the intercoolers. I can see where the bilge exhaust exits but can not figure out how the air intakes with all the insulation etc. Is it just blanket air. Would intake fans help? Any thoughts? I hope this is doing it right as I am a dinosaur with computers.
  9. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    13,933
    Location:
    Fort Lauderdale
    When you run at cruise speed, is it hard to open the engine room door? You can install a vaccuum gauge and see what vaccuum the engine room has when at cruise speed. But if the engine room door is being sucked shut, that is the first indication that your vents are too small.
  10. rtrafford

    rtrafford Senior Member

    Joined:
    Jul 13, 2019
    Messages:
    989
    Location:
    Vero Beach
    Dumping lots of clean fresh air into the ER from a dry source is always a benefit. Engines love cooler, clean air. Engine rooms love cooler clean air to push the heat out after running. So if there is a straight forward method of pumping air in to add to the situation, look into doing it. Look up the specs on your engines. You'll be in awe of how much air they consume to run at speed...

    I run with all of my vents open AND with two high flow volume DC blowers pulling filtered air into the ER. The blowers make a very big difference.
  11. Beau

    Beau Senior Member

    Joined:
    Jan 15, 2010
    Messages:
    2,266
    Location:
    Beaufort, NC
    Restricted air flow into the engine room is normally not the result of inaccurate design in popular boats that have been around awhile. Is there any general complaint about that from other owners? It's usually because something has been changed or unwittingly restricted. The engine room door is the usual first test at rpm for low air flow. Most vessels have other areas for ER air such as over the top of the cockpit liner or thru the bilge that draws fresh air from areas or vents in the living area. Some boats also use a built in snorkel. Most ER blowers move about 400 CFM and one may vent in, the other vent out (I have 4). Hard to imagine those making a big difference to air flow running at RPM, and an ER fan is only good for moving air around. It's good for dispersing hot air as it collects, but it will not add air to the ER. Crushed filters can often occur from undersized filters or allowing them to clog. Is the OPs complaint lack of air or wet air passing thru an unprotected side vent? Many vessels have a rectangular box covering the inside of the side vents with an open top like a flower box, or similar structure. This knocks down water droplets and lets them collect in the box and naturally drain Hard to completely "dry" the air coming in when you have side vents - the air naturally has a higher content of water by the natural throw of salt water from the hull at speed

    So after you determine the ER door is difficult to open here is another test. Take the boat out , get everything up to temp and run up to your cruising rpm. Then have some one open a cockpit hatch or the ER door while you monitor your tachs. Did you gain any RPM? Are you exhausting less smoke?
    Last edited: Jun 4, 2020
  12. mapism

    mapism Senior Member

    Joined:
    Aug 9, 2008
    Messages:
    1,406
    Location:
    Sardinia
    Good advice, but unless the OP retrofitted some digital tachos, it's very unlikely that the rpm increase could be noticeable, on some 1984 analogue gauges. Same goes for exhaust, which on such old engines would hardly be affected a lot by better breathing.
    Short of fitting a vacuum gauge as CaptJ suggested, I don't think there's much more that can be done aside from "feeling" any suction upon opening of the e/r door.

    Anyway, to answer his question about fans, actually they are more meant to circulate air and cool down the e/r a bit AFTER running the boat, rather than while cruising. Diesel engines are essentially massive air pumps, and if they can't pull in all the air they need due to intake restrictions, no fans can solve such problem.
  13. Beau

    Beau Senior Member

    Joined:
    Jan 15, 2010
    Messages:
    2,266
    Location:
    Beaufort, NC
    It's only another test like looking for negative pressure on a door. Why would a 1984 boat that is fairly popular all of a sudden develop insufficient combustion aeration? I'm thinking that's not his problem, or something was modified that restricts that flow - maybe by a former owner? Is insufficient air a generic complaint on that model?

    The unguarded air vent is a concern because the outboard side of that engine and every thing else located there is probably getting "splashed" to some degree while on plane. Also, if the hull rinses and washes are not done carefully that hose stream is going right into the engine room. Mike G. have you gone outboard on that side to look at your equipment?
    Last edited: Jun 5, 2020
  14. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    13,933
    Location:
    Fort Lauderdale
    It's a lot more common than you think with Sportfish. I've seen some hulls with molded in engine room vents origionally designed for 660 HP diesels when first introduced end up with 1100 HP diesels installed by the factory a few years later. A lot of times a SF will be built, even big ones, and the largest engine at the time might be 1600HP, but 3 years later same engine puts out 1900 hp or they're installing 2600 HP diesels. Well the origional air vents in the mold generally stay the same. So don't always expect that the builder got it right.
  15. Beau

    Beau Senior Member

    Joined:
    Jan 15, 2010
    Messages:
    2,266
    Location:
    Beaufort, NC
    Agree with you. My focus was more on end user complaints. Has lack of air been a common complaint? This is a 1984 manufacture. Has the boat been repowered?
  16. mapism

    mapism Senior Member

    Joined:
    Aug 9, 2008
    Messages:
    1,406
    Location:
    Sardinia
    Yup, this is the crux of the matter.
    Actually I didn't understand up to when everything was fine, because the OP said that he "always had intake and filter collapse problems" during his 10 years of ownership.
    Which on one hand suggests that the problem (if any) couldn't be so huge, but otoh raises the suspicion that in between 1984 and 10 years ago something happened that restricted the intakes.
    Maybe tearing apart the boat for education as NYCAP suggested is the most appropriate course of action, all considered...
  17. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    13,933
    Location:
    Fort Lauderdale
    It could be that the air vents are borderline in a normal climate and the hotter Mexican air and the engines need more air as it's less dense. Perhaps cutting a hole under the gunnel and running a 4" blower into the engine room would help with airflow.
  18. Beau

    Beau Senior Member

    Joined:
    Jan 15, 2010
    Messages:
    2,266
    Location:
    Beaufort, NC
    If air restriction is in fact a problem, he could also create a convenient opening to additional air somewhere outside the ER and lay in a 6" tube or tubes that simple allows the engines to draw the air thru? Staying away from any "station wagon" affected air source. The simple inertia of moving forward and using a scooping device would be good also.. I'm still not convinced he has an aeration problem, unless he had his motors upgraded to Capt J's point, or something was changed post production. Dunno....

    Do you hear any whistling from an imperfect hatch or door seal? See any telltail dirt streaks indicating a sucking air source?
  19. d_meister

    d_meister Senior Member

    Joined:
    Mar 4, 2010
    Messages:
    427
    Location:
    San Diego, CA.
    Did these boats come with fire suppression doors on the intakes? If so, it could be one dropped shut, or something along those lines. Odd that port and starboard are dissimilar.
  20. mapism

    mapism Senior Member

    Joined:
    Aug 9, 2008
    Messages:
    1,406
    Location:
    Sardinia
    Good idea.
    The odds of one intake flap dropping shut are probably very low, but if the fire system for any reason (possibly just due to a fault) shut them, one might have remained stuck closed upon re-opening, unnoticed to the owner.
    A possibility worth checking, anyway.
    Even if I wouldn't be surprised if a 1984 boat would have no fire flaps at all on the E/R air intakes...