Groundhog Day

[Compass790]

I'll let someone who is familiar with the 2GM20 comment on its vibration but if your motor mounts are perished, cracked or sagging it's time to replace.
The other thing to check is the engine to prop shaft alignment. I'm not going to attempt a written tutorial on that as there are vids on utube explaining that better than I can write. Look for the one that uses feeler gauges. Dont do the alignment till after you get new motor mounts if they need replacing. Apologies if I'm stating the obvious but it may not be obvious to a newbie.
Alignment is a bugger of a job if access is limited & its always limited on a small yacht but if it hasnt been done for 20 years it should be done.
Yanmar engine mounts are a kings ransom. You can get much cheaper aftermarket ones should you need new ones. Parts4engines is one option, there will be others.
Hope that helps.

[Wotname]

Originally Posted by djousset

Thanks all, it sure feels good to have gotten to the other side.
............... Also a link to the shaft, how much vibration is ok? This was at idle.


https://photos.app.goo.gl/EhuV1X2RPpYHrHNg8

OK, being as no one else is responding to the vibration question, I'll jump in and have a stab at it.

First of all, the 2GM20 does vibrate and when in gear, they may (will?) have 'rough' spots over the rev range which is very installation dependent. For instance, I had to avoid 2,500 rpm but anything else was fine with my 2GM20 however other installations were OK at 2,500 rpm. The operator's manual warns about this!

Do you have a tach fitted, if so, what was the idle rpm in the link as to my ears it sounded a little high - but I won't trust my ears .

As to the vibration, it looked a tiny bit more than I would expect but this is certainly not a definitive diagnosis. I would rather see what it looked like over a range of rpm (say 800 to 1,200) and again over the full range (all in neutral) and then again loaded up (i.e in gear). The drive train setup will have a huge bearing on vibrations when in gear.

Disclaimer - I don't have a wealth of experience in various prop and shaft setups.

[Wotname]

Oh...look - cross posted with Compass790

[kaisardog]

"..I see no signs of a leak anywhere, and there’s no air from the fuel tank, to the lift pump, to the secondary filter, but I did discover diesel fuel in the pan under the engine, which I've not seen before. I assume this means there IS a leak. And in a place I am not qualified to touch..." 1/ note that on the yan 2 GM20 F when you mess with or change the no 2 fuel filter (closest to the injectors) you are supposed to use a new copper washer, or anneal the old one. a leak at this washer lets air in and can cause problems.. 2/ you say you see diesel fuel around the mechanical pump and or fuel lines between RACOR and 2ndary filter ? 1st carefully check your fuel hoses into/ out of the RACOR especially if t hey're old. then consider the possibility that in an old engine you my have a diaphragm crakc or other issue in the mechanical lift pump. a small undetectable crack in an old fuel hose , which only leaks when under pressure from the fuel pump, is hard to find. try the smell test: taking clean paper towels, paper towels, wipe the fuel hose going from RACOR to mechanical pump to RACOR one inch at a time. smell the paper towel, if you smell diesel you've found a microcrack in the fuel hose. 3/ YOU ARE the most qualified to fix this problem, the 'pro' will just repeat what you've done and charge $$$. I'd search for and read all the posts on 'diesel problem.. engine cutting out' on various internet diesel engine forums including this one. take notes and try other owner's suggestions. (and let us know what you find ...)

[kaisardog]

you might check this post in the engine forum :"Re: Help w/ Yanmar 3JH3 Power Drop-Off Mystery.' the suggestions include an interesting idea of checking for an air leak by having a mechanical squeeze bulb connected to a clear length of tubing, putting that bulb into your system to replace various pieces of existing fuel hose like RACOR to mechanical pump then mechsnical to 2 degree filter body, etc. and seeing where you have air bubbles showing in the clear plastic line. (presumably the clear plastic chosen is of sufficient strength to not collapse under the pressure created by the squeeze bulb or engine's fuel pump. ) it's not clear to me from that post whether the engine is supposed to be running with fuel supplied off a day tank , or off the main fuel tank.

[Wotname]

Originally Posted by kaisardog

.......(and let us know what you find ...)

Have a look at post #44 (and a few preceding ones)!

[Compass790]

Originally Posted by Wotname

Oh...look - cross posted with Compass790

Yea Wottie but you are an ex 2GM20 owner so at least you know what you are looking at.
To a Gold stamper owner ( ysm8 single) it doesnt look too bad but it's a long time since I've been on a 2gm20 powered yacht.
Good point Wottie about sweet rev spot, most diesels have 'em, ours varies between hammering on the feet or teeth rattling

[Wotname]

Originally Posted by kaisardog

"............
1/ note that on the yan 2 GM20 F when you mess with or change the no 2 fuel filter (closest to the injectors) you are supposed to use a new copper washer, or anneal the old one. a leak at this washer lets air in and can cause problems.. .........

You raise a good point as the bleed screw on this filter is usually the high point of the fuel piping and is prone to letting in air. The thread in the filter housing is often loose or partially stripped. It is an alloy housing and people torque up the steel bleed screw trying to get the old washer to seal and in doing so, destroy the thread in the filter head.

You might be interested to know that Yanmar is now using a softer nylon (or some other composite) washer under this bleed screw. It saves torquing hard on the bleed screw to get it to seal.

Djousset, you might want to check how good the thread is on the engine filter bleed screw and replace any copper washer there with a composite (fibre/nylon) one.

[djousset]

@compass and wotname. Thanks for the tips on the vibration. I will look over the mounts and check out alignment on Youtube. I'll watch it under varying speeds and see if there's anything to note. Sadly the tach recently stopped registering sooo..... that's a new thing to look into. Maybe a simple fix

Relative to the bleed screw at the engine filter, I did check that during my lengthy air-leak diagnostics foray, all looked good. I did replace the copper washers but the composite makes sense.

[Wotname]

Originally Posted by djousset

......... Sadly the tach recently stopped registering sooo..... that's a new thing to look into. Maybe a simple fix

..........

Yes, it is often a simple fix!

Assuming you have the standard Yanmar supplied tach, the most likely culprit is the corrosion or loose terminals on the tach sender; mounted near the top of the bell housing just to the port side.

Next most likely is corrosion in the engine loom connector.

After that, it requires a bit more in depth troubleshooting but nothing you can't handle.

[Shaneesprit]

Yanmar
From what I see on other posts - always suspect the fuel lift pump.
Although my personal experience on Yanmar engines has always been good

[Compass790]

Yea Wottie is on the ball as usual, we had continous problems with the wiring loom plug for tach ( trace wire back from flywheel sender ) as our engine shakes pretty violently so eventually the fix was to cable tie the two 1/2's of the plug together.
Personally I ditched the yanmar engine mounted fuel filter mount as the dinky little filters are overpriced & have to be changed at 100 hrs whereas you can get one that has replacement filters that cost 1/2 as much & last for 500hrs+.
Also i mounted it off engine to be easier to get at & keep fuel cooler but I must admit I noticed no power increase lol.
You can get non-yanmar replacement filter cartridges for yr engine mounted original a lot cheaper but I don't know where in the USA, fleabay might be worth a look.
Agree with Wottie again ( boring isnt it) about nylon/composite crush washers but I wouldnt touch it now you have new copper ones on if it isnt leaking.

[fnq grumpy]

Recently had not dis-similar problem with RO plant feed pump losing prime and all the usual things didn't get it solved.
Sufficient frustration eventually overcame laziness and isolated complete system at high pressure pump, got it empty ie full of air, sorted out fittings and a shrader valve (tyre valve)and pressurised the whole lot to 5 psi back to hull shut off valve with a 12v tyre pump.
Around and about with soapy water showed leaks I was sure were not there, sorted them one by one until it help pressure for 24 hrs. Problem solved. Should have done that many false 'fixed nows' ago.

Leaking air is much easier to find than leaking fluid in my experience even if there is a bit of a pain setting it up.

Something to think about if desperate enough.

[sailingharry]

Originally Posted by Shaneesprit

Yanmar
From what I see on other posts - always suspect the fuel lift pump.
Although my personal experience on Yanmar engines has always been good

Can you elaborate on what to suspect on the lift pump? I am also chasing air issues on my Yanmar, and I am beginning to suspect an air leak in the lift pump.

[djousset]

Originally Posted by Wotname

Yes, it is often a simple fix!

Assuming you have the standard Yanmar supplied tach, the most likely culprit is the corrosion or loose terminals on the tach sender; mounted near the top of the bell housing just to the port side.

Next most likely is corrosion in the engine loom connector.

After that, it requires a bit more in depth troubleshooting but nothing you can't handle.

After I looked up what a "bell housing" and "loom connector" were ..... I checked/jiggled/pushed the wires at the panel in the cockpit and then at the engine and guess what? Perhaps all my fussing around with the engine loosened something, can't say what but happy it's back up! Thank you