9KW Onan generator intake hose collapses

Discussion in 'General Discussion' started by Alex F, Jul 6, 2020.

  1. Alex F

    Alex F Well-Known Member

    Nov 14, 2006
    East Coast
    2005 420DB with AB 11 DLX Tender, Raymarine Dual E120 MFD/Radar/XMWeather, ST7001 A/P, AIS, SeaLift
    T-Cummins 450Cs Straight-Drives, 9KW Onan Generator, 40HP Yamaha for tender.
    I've heard this before, but never had first hand experience until now. My genny's intake hose collapses after few hours of run time. I guess it relates to rise in temp in the ER. All gauges on the unit show normal readings, but I clearly see collapsed intake hose, which raises a great deal of a concern.

    Does anyone know if there's a replacement reinforced hose?
     

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  2. Sublimetime

    Sublimetime Active Member

    847
    Oct 22, 2007
    clifton nj
    420 da
    454
    If it is collapsing that would indicate a restriction before the pump causing the suction of the pump to create a vacuum inside. Probably a clogged thru-hull strainer on the outside of the boat.
     
    dtfeld likes this.
  3. Alex F

    Alex F Well-Known Member

    Nov 14, 2006
    East Coast
    2005 420DB with AB 11 DLX Tender, Raymarine Dual E120 MFD/Radar/XMWeather, ST7001 A/P, AIS, SeaLift
    T-Cummins 450Cs Straight-Drives, 9KW Onan Generator, 40HP Yamaha for tender.
    That was my first thought as well. I opened the strainer and plenty of water was coming through. I also dove to inspect the scoop strainer and made sure it's free of any obstruction. Still the hose is collapsing.

    I wonder if the new hoses are now reinforced.
     
  4. blaster

    blaster Well-Known Member SILVER Sponsor

    May 23, 2011
    potomac river
    2010 sea ray 205 sport
    F-250 CCLB 6.2 4x4 3.73 rear.
    Mercruiser 4.3 mpi alpha 1.62
    Is this an original hose? I have had many cooling hoses bulge or collapse when worn out. If this is a new hose it’s junk!
     
  5. my3sons

    my3sons Well-Known Member GOLD Sponsor

    Feb 24, 2009
    NY (Lake Erie)
    2004 400DB, Onan 9 kw Gen, Highfield RIB,
    Cummins 6CTA
    Just a thought, have you tried back flushing that hose? The pipe that crosses over from the backside is smaller diameter than the hose. Something might be hung up in there. Also could have growth in that metal pipe??
     
  6. Henry Boyd

    Henry Boyd Well-Known Member GOLD Sponsor

    Apr 24, 2007
    Newburyport, on the peaceful and serene Merrimack
    ‘09 Sabre 38 Hardtop Express “Serenity”
    Volvo D6 w/IPS450 Pods
    Alex,

    Do you have the Remote control with lcd display? If so, with the engine running, is the engine temp on spec, or running hot?
     
  7. Alex F

    Alex F Well-Known Member

    Nov 14, 2006
    East Coast
    2005 420DB with AB 11 DLX Tender, Raymarine Dual E120 MFD/Radar/XMWeather, ST7001 A/P, AIS, SeaLift
    T-Cummins 450Cs Straight-Drives, 9KW Onan Generator, 40HP Yamaha for tender.
    The interesting part is that I don't see any difference in water coming in or out of the exhaust. For this reason, I don't think there's a restriction. The only last thing I have left to do, to verify no intake restriction, is to dive and inspect/clean every small hole in my strainter (I have external screens for each intake). There's always a chance that some barnacle growth could be between the screen and the scoop, which is impossible to see unless the screen is removed. Unfortunately, the one I have for genny, is not serviceable.

    The hose is definitely not original, but at this point it's due for replacement. I just wanted to run it by the forum to see if anyone found different type of hose, so I don't use the same non-reinforced version.

    Mark,
    I got rid of the pipe wile ago. I replaced it once and it lasted short two years before it turned into a "sprinkler". Since I don't have a sound shield, it was an easy decision to route reinforced hose around the HE, rather than under the engine. There's only room for that crappy pipe, but not for reinforced hose. Worked like a charm.

    Henry,
    The external panel has gauges with digital dots with changing colors (red, yellow, green). All show green, indicating normal temps.

    The genny ran all day with collapsed hose and no changes, while I was periodically checking the temps and the exhaust. There's also exhaust temp sensor, so if the exhaust got too hot, despite what my eyes could see at the discharge, the sensor would trigger the shutdown event.
     
  8. Irie308

    Irie308 Well-Known Member SILVER Sponsor

    May 28, 2013
    CT
    2004 420 Sedan Bridge, GHS Hydraulic Lift
    Dual Raymarine E120W
    AB Mares 10 VSX with 30 hp Tohatsu
    Cummins 450C 8.3 L Turbocharged
    Alex, when we were in Mystic last year we kept pulling in sea grass. My gen doesn't have a screen. What i did to reslove this while anchored was to swap the hose with the AC pickup which has a scoop strainer. This was fine while anchored but I made sure to swap it back before we went underway to avoid forcing water into the gen while running. Not sure if your external screens are the same on each side but could you try swapping hoses? I also had clogs so bad that i disconnected the hose at times and hooked it up to the foot pump for my dinghy to force out any obstructions.
     
  9. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    Alex,

    What you are looking for is a Shield's Series-250 or Series-252 hose, both of which are reinforced with a metal wire helix to prevent collapse. Lengths are available at West Marine.

    I'm having trouble getting a lock on what ID size your hose is. Most are 3/4" hose but the I would take a piece with you.
     
  10. Alex F

    Alex F Well-Known Member

    Nov 14, 2006
    East Coast
    2005 420DB with AB 11 DLX Tender, Raymarine Dual E120 MFD/Radar/XMWeather, ST7001 A/P, AIS, SeaLift
    T-Cummins 450Cs Straight-Drives, 9KW Onan Generator, 40HP Yamaha for tender.
    :).....Dean, this brings some good memories. I think you were in the same raft with us few years back in Block. This is when the salt pond was infested with tons of jelly fish. I was shocked when they passed my screens and clogged my genny's intake so badly that no water was coming through. A back flush at 55psi would clear it. So, knowing that I need my genny more than AC, I swapped my hoses and used AC's strainer to feed the gen. Magically, overnight, the clogged genny's pickup cleared itself.

    The key part in this situation that I don't see an obvious obstruction, as I have decent water flow from the seastrainer to the water pump. If there's anything in the screen, the restriction is very minor. At this time, I'm suspecting the following contributing items:
    1. Elevated temps (water...it's in upper 80s and air in ER).
    2. Age of the hose. It looks good, but hasn't been replaced in few years.

    When I spoke to Cummins parts dept and asked about new version of the hose to reinforced, they just had no clue. I ordered the regular old type, just to rule the "old hose" theory out.

    John,
    It would be a super easy fix if the hose was straight. The intake and outgoing from/to the raw water pump have sharp 90 degrees turn. A regular reinforced hose wouldn't be able to make that turn without sticking out too far out. The hoses you described is what I used in the past. If it wasn't for the short and sharp turn at the pump, I'd run it all the way to the pump.

    I have few ideas, if the new hose will also collapse. I'll keep you guys updated on how this situation unfolds. It'll be solved one way or the other.
     
    Last edited: Jul 11, 2020
    PlayDate likes this.
  11. Alex F

    Alex F Well-Known Member

    Nov 14, 2006
    East Coast
    2005 420DB with AB 11 DLX Tender, Raymarine Dual E120 MFD/Radar/XMWeather, ST7001 A/P, AIS, SeaLift
    T-Cummins 450Cs Straight-Drives, 9KW Onan Generator, 40HP Yamaha for tender.
    Quick update:

    I took my diving rig and decided to give closer look and extra cleaning of the screen. I used small pick tool to clean every hole in the screen to ensure that I loosen anything that can be stuck between the screen and the through hull. I also replaced both hoses (from/to the raw water pump).

    The issue of collapsing hose has been solved.
     
    PlayDate and Jaybeaux like this.

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