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10-05-2020, 08:30
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#1
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Registered User
Join Date: May 2020
Posts: 2
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Yanmar 2GM20F leaky adjustment screw
Hi folks,
my first post here! (long time lurker)
Our Yanmar 2GM20F has an adjustment screw that has been leaking raw water for some time it appears. It is located on the SB/FWD side of the engine.
I looked through the manual, but somehow failed to locate what this screw is for. It was wired to the block, so I assume it is not to be touched frequently.
Any insights? Pretty disconcerting amount of corrosion there...Thanks!
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10-05-2020, 08:43
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#2
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Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,483
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Re: Yanmar 2GM20F leaky adjustment screw
That appears to be the injection pump adjustment. Dont move it! Why do you think it's leaking? I see corrosion around it, but that's from salt water. The pump has diesel in it.
The corrosion could be from various things, former work, hose leak, heavy weather/green water getting below into the engine compartment or etc. Is anything wet now?
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
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10-05-2020, 09:18
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#3
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Marine Service Provider
Join Date: Jan 2013
Location: Kimberton,Pa.
Boat: Cabo Rico 34
Posts: 1,028
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Re: Yanmar 2GM20F leaky adjustment screw
Appears to be possibly a raw water leak somewhere above the “screw” mentioned... Run the engine and observe...
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10-05-2020, 10:24
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#4
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Registered User
Join Date: May 2020
Posts: 2
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Re: Yanmar 2GM20F leaky adjustment screw
Thanks for the replies. It was dry when I found it, but judging from the corrosion it seemed like it was coming from there. That doesn’t make sense if it's part of the injection pump of course. I didn’t change the adjustment not knowing what it was though the locking wire did snap off being so corroded.
I’ll investigate more and report back!
Thanks for the replies
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10-05-2020, 15:24
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#5
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Marine Service Provider
Join Date: Sep 2014
Location: Auckland, NZ
Boat: Compass 790 , 7.9 metres or 26 ft
Posts: 2,803
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Re: Yanmar 2GM20F leaky adjustment screw
Quote:
Originally Posted by gatorjos
Thanks for the replies. It was dry when I found it, but judging from the corrosion it seemed like it was coming from there. That doesn’t make sense if it's part of the injection pump of course. I didn’t change the adjustment not knowing what it was though the locking wire did snap off being so corroded.
I’ll investigate more and report back!
Thanks for the replies
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Yep I'm with the other 2 posts, definitely not coming from the adjustment screw opening or it would be rusty. Whilst I'm not familiar with the 2gm20 cooling layout it's likely its from a raw water hose drip.
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10-05-2020, 16:21
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#6
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,305
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Re: Yanmar 2GM20F leaky adjustment screw
Quote:
Originally Posted by gatorjos
Thanks for the replies. It was dry when I found it, but judging from the corrosion it seemed like it was coming from there. That doesn’t make sense if it's part of the injection pump of course. I didn’t change the adjustment not knowing what it was though the locking wire did snap off being so corroded.
I’ll investigate more and report back!
Thanks for the replies
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Welcome aboard CF, gatorjos.
It is the No Load Maximum Speed Limiter part of the governor - essentially sets the maximum idle speed and is factory set as part of the engine's emission controls. It isn't the end of the earth if it has moved slightly but of course, it is best left alone.
The corrosion is almost certainly being caused by a raw water leak from somewhere in the heat exchanger / exhaust manifold which is directly above the governor housing. It could be as simple as dripping hose but it may be far more serious. Hunt it down!!!
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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10-05-2020, 16:28
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#7
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,305
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Re: Yanmar 2GM20F leaky adjustment screw
Quote:
Originally Posted by gatorjos
..........
I looked through the manual, but somehow failed to locate what this screw is for. It was wired to the block, so I assume it is not to be touched frequently.
..........
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FWIW
In my service manual, the governor system is chapter 4 and the heat exchanger / manifold is in chapter 8.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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10-05-2020, 18:33
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#8
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Moderator
Join Date: Feb 2010
Location: Australia
Posts: 3,252
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Re: Yanmar 2GM20F leaky adjustment screw
If you’re lucky it’s the raw water hose between the pump and heat exchanger........unlucky would be a leaking heat exchanger end cap, assuming this is a raw water leak and not from, say, the engine hatch or cockpit floor.
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11-05-2020, 09:07
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#9
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Registered User
Join Date: Jan 2014
Location: Ft. Lauderdale
Boat: Watkins 29
Posts: 409
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Re: Yanmar 2GM20F leaky adjustment screw
I had a similar problem with my engine! The hose from the raw water pump that winds its way up to the heat exchanger was worn out right where it connects to the heat exchanger input port! Mine dripped salt water on the throttle lever where it goes into the fuel injection pump . Right above the engine shut off cable!. My throttle at times is very difficult to move at times and requires extra lubrication!
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11-05-2020, 13:26
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#10
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Registered User
Join Date: Aug 2011
Location: West Sussex, United Kingdom
Boat: Tradewind 33, 33 foot, Parker 27 , 26 foot
Posts: 496
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Re: Yanmar 2GM20F leaky adjustment screw
Quote:
Originally Posted by Wotname
Welcome aboard CF, gatorjos.
It is the No Load Maximum Speed Limiter part of the governor - essentially sets the maximum idle speed and is factory set as part of the engine's emission controls. It isn't the end of the earth if it has moved slightly but of course, it is best left alone.
The corrosion is almost certainly being caused by a raw water leak from somewhere in the heat exchanger / exhaust manifold which is directly above the governor housing. It could be as simple as dripping hose but it may be far more serious. Hunt it down!!!
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I second that. It is a bit hard to find but if you have the Seloc Yanmar Inboards 1975-98 Repair Manual its on page 4-21 of the fuel system. It's wire locked together with the same piece of locking wire with the Fuel Injection Limiter which is on the vertical face below it on the forward face.
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11-05-2020, 15:41
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#11
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,305
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Re: Yanmar 2GM20F leaky adjustment screw
FWIW, there is _GM & _HM Yanmar service manual available for download in the CF Library (Manuals) area. This covers the OP engine.
https://www.cruisersforum.com/forums...id=1&sort=date
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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